com.accelad.math.nilgiri.bigdecimal.BigDecimalMath Maven / Gradle / Ivy
package com.accelad.math.nilgiri.bigdecimal;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.MathContext;
import java.security.ProviderException;
public class BigDecimalMath {
static BigDecimal E = new BigDecimal(
"2.71828182845904523536028747135266249775724709369995957496696762772407663035354"
+ "759457138217852516642742746639193200305992181741359662904357290033429526059563"
+ "073813232862794349076323382988075319525101901157383418793070215408914993488416"
+ "750924476146066808226480016847741185374234544243710753907774499206955170276183"
+ "860626133138458300075204493382656029760673711320070932870912744374704723069697"
+ "720931014169283681902551510865746377211125238978442505695369677078544996996794"
+ "686445490598793163688923009879312773617821542499922957635148220826989519366803"
+ "318252886939849646510582093923982948879332036250944311730123819706841614039701"
+ "983767932068328237646480429531180232878250981945581530175671736133206981125099"
+ "618188159304169035159888851934580727386673858942287922849989208680582574927961"
+ "048419844436346324496848756023362482704197862320900216099023530436994184914631"
+ "409343173814364054625315209618369088870701676839642437814059271456354906130310"
+ "720851038375051011574770417189861068739696552126715468895703503540212340784981"
+ "933432106817012100562788023519303322474501585390473041995777709350366041699732"
+ "972508868769664035557071622684471625607988265178713419512466520103059212366771"
+ "943252786753985589448969709640975459185695638023637016211204774272283648961342"
+ "251644507818244235294863637214174023889344124796357437026375529444833799801612"
+ "549227850925778256209262264832627793338656648162772516401910590049164499828931");
static BigDecimal PI = new BigDecimal(
"3.14159265358979323846264338327950288419716939937510582097494459230781640628620"
+ "899862803482534211706798214808651328230664709384460955058223172535940812848111"
+ "745028410270193852110555964462294895493038196442881097566593344612847564823378"
+ "678316527120190914564856692346034861045432664821339360726024914127372458700660"
+ "631558817488152092096282925409171536436789259036001133053054882046652138414695"
+ "194151160943305727036575959195309218611738193261179310511854807446237996274956"
+ "735188575272489122793818301194912983367336244065664308602139494639522473719070"
+ "217986094370277053921717629317675238467481846766940513200056812714526356082778"
+ "577134275778960917363717872146844090122495343014654958537105079227968925892354"
+ "201995611212902196086403441815981362977477130996051870721134999999837297804995"
+ "105973173281609631859502445945534690830264252230825334468503526193118817101000"
+ "313783875288658753320838142061717766914730359825349042875546873115956286388235"
+ "378759375195778185778053217122680661300192787661119590921642019893809525720106"
+ "548586327886593615338182796823030195203530185296899577362259941389124972177528"
+ "347913151557485724245415069595082953311686172785588907509838175463746493931925"
+ "506040092770167113900984882401285836160356370766010471018194295559619894676783"
+ "744944825537977472684710404753464620804668425906949129331367702898915210475216"
+ "205696602405803815019351125338243003558764024749647326391419927260426992279678"
+ "235478163600934172164121992458631503028618297455570674983850549458858692699569"
+ "092721079750930295532116534498720275596023648066549911988183479775356636980742"
+ "654252786255181841757467289097777279380008164706001614524919217321721477235014");
static BigDecimal GAMMA = new BigDecimal("0.577215664901532860606512090082402431"
+ "0421593359399235988057672348848677267776646709369470632917467495146314472498070"
+ "8248096050401448654283622417399764492353625350033374293733773767394279259525824"
+ "7094916008735203948165670853233151776611528621199501507984793745085705740029921"
+ "3547861466940296043254215190587755352673313992540129674205137541395491116851028"
+ "0798423487758720503843109399736137255306088933126760017247953783675927135157722"
+ "6102734929139407984301034177717780881549570661075010161916633401522789358679654"
+ "9725203621287922655595366962817638879272680132431010476505963703947394957638906"
+ "5729679296010090151251959509222435014093498712282479497471956469763185066761290"
+ "6381105182419744486783638086174945516989279230187739107294578155431600500218284"
+ "4096053772434203285478367015177394398700302370339518328690001558193988042707411"
+ "5422278197165230110735658339673487176504919418123000406546931429992977795693031"
+ "0050308630341856980323108369164002589297089098548682577736428825395492587362959"
+ "6133298574739302373438847070370284412920166417850248733379080562754998434590761"
+ "6431671031467107223700218107450444186647591348036690255324586254422253451813879"
+ "1243457350136129778227828814894590986384600629316947188714958752549236649352047"
+ "3243641097268276160877595088095126208404544477992299157248292516251278427659657"
+ "0832146102982146179519579590959227042089896279712553632179488737642106606070659"
+ "8256199010288075612519913751167821764361905705844078357350158005607745793421314"
+ "49885007864151716151945");
static BigDecimal LOG2 = new BigDecimal("0.693147180559945309417232121458176568075"
+ "50013436025525412068000949339362196969471560586332699641868754200148102057068573"
+ "368552023575813055703267075163507596193072757082837143519030703862389167347112335"
+ "011536449795523912047517268157493206515552473413952588295045300709532636664265410"
+ "423915781495204374043038550080194417064167151864471283996817178454695702627163106"
+ "454615025720740248163777338963855069526066834113727387372292895649354702576265209"
+ "885969320196505855476470330679365443254763274495125040606943814710468994650622016"
+ "772042452452961268794654619316517468139267250410380254625965686914419287160829380"
+ "317271436778265487756648508567407764845146443994046142260319309673540257444607030"
+ "809608504748663852313818167675143866747664789088143714198549423151997354880375165"
+ "861275352916610007105355824987941472950929311389715599820565439287170007218085761"
+ "025236889213244971389320378439353088774825970171559107088236836275898425891853530"
+ "243634214367061189236789192372314672321720534016492568727477823445353476481149418"
+ "642386776774406069562657379600867076257199184734022651462837904883062033061144630"
+ "073719489002743643965002580936519443041191150608094879306786515887090060520346842"
+ "973619384128965255653968602219412292420757432175748909770675268711581705113700915"
+ "894266547859596489065305846025866838294002283300538207400567705304678700184162404"
+ "418833232798386349001563121889560650553151272199398332030751408426091479001265168"
+ "243443893572472788205486271552741877243002489794540196187233980860831664811490930"
+ "667519339312890431641370681397776498176974868903887789991296503619270710889264105"
+ "230924783917373501229842420499568935992206602204654941510613");
static public BigDecimal pi(final MathContext mc) {
/* look it up if possible */
if (mc.getPrecision() < PI.precision())
return PI.round(mc);
else {
/*
* Broadhurst arXiv:math/9803067
*/
int[] a = { 1, 0, 0, -1, -1, -1, 0, 0 };
BigDecimal S = broadhurstBBP(1, 1, a, mc);
return multiplyRound(S, 8);
}
} /* BigDecimalMath.pi */
static public BigDecimal gamma(MathContext mc) {
/* look it up if possible */
if (mc.getPrecision() < GAMMA.precision())
return GAMMA.round(mc);
else {
double eps = prec2err(0.577, mc.getPrecision());
/*
* Euler-Stieltjes as shown in Dilcher, Aequat Math 48 (1) (1994)
* 55-85
*/
MathContext mcloc = new MathContext(2 + mc.getPrecision());
BigDecimal resul = BigDecimal.ONE;
resul = resul.add(log(2, mcloc));
resul = resul.subtract(log(3, mcloc));
/*
* how many terms: zeta-1 falls as 1/2^(2n+1), so the terms drop
* faster than 1/2^(4n+2). Set 1/2^(4kmax+2) < eps. Leading term
* zeta(3)/(4^1*3) is 0.017. Leading zeta(3) is 1.2. Log(2) is 0.7
*/
int kmax = (int) ((Math.log(eps / 0.7) - 2.) / 4.);
mcloc = new MathContext(1 + err2prec(1.2, eps / kmax));
for (int n = 1;; n++) {
/*
* zeta is close to 1. Division of zeta-1 through 4^n*(2n+1)
* means divion through roughly 2^(2n+1)
*/
BigDecimal c = zeta(2 * n + 1, mcloc).subtract(BigDecimal.ONE);
BigInteger fourn = new BigInteger("" + (2 * n + 1));
fourn = fourn.shiftLeft(2 * n);
c = divideRound(c, fourn);
resul = resul.subtract(c);
if (c.doubleValue() < 0.1 * eps)
break;
}
return resul.round(mc);
}
} /* BigDecimalMath.gamma */
static public BigDecimal sqrt(final BigDecimal x, final MathContext mc) {
if (x.compareTo(BigDecimal.ZERO) < 0)
throw new ArithmeticException("negative argument " + x.toString() + " of square root");
if (x.abs().subtract(new BigDecimal(Math.pow(10., -mc.getPrecision())))
.compareTo(BigDecimal.ZERO) < 0)
return BigDecimalMath.scalePrec(BigDecimal.ZERO, mc);
/* start the computation from a double precision estimate */
BigDecimal s = new BigDecimal(Math.sqrt(x.doubleValue()), mc);
final BigDecimal half = new BigDecimal("2");
/* increase the local accuracy by 2 digits */
MathContext locmc = new MathContext(mc.getPrecision() + 2, mc.getRoundingMode());
/*
* relative accuracy requested is 10^(-precision)
*/
final double eps = Math.pow(10.0, -mc.getPrecision());
for (;;) {
/*
* s = s -(s/2-x/2s); test correction s-x/s for being smaller than
* the precision requested. The relative correction is 1-x/s^2,
* (actually half of this, which we use for a little bit of
* additional protection).
*/
if (Math.abs(
BigDecimal.ONE.subtract(x.divide(s.pow(2, locmc), locmc)).doubleValue()) < eps)
break;
s = s.add(x.divide(s, locmc)).divide(half, locmc);
/*
* debugging System.out.println("itr "+x.round(locmc).toString() +
* " " + s.round(locmc).toString()) ;
*/
}
return s;
} /* BigDecimalMath.sqrt */
static public BigDecimal sqrt(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) < 0)
throw new ArithmeticException("negative argument " + x.toString() + " of square root");
return root(2, x);
} /* BigDecimalMath.sqrt */
static public BigDecimal cbrt(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) < 0)
return root(3, x.negate()).negate();
else
return root(3, x);
} /* BigDecimalMath.cbrt */
static public BigDecimal root(final int n, final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) < 0)
throw new ArithmeticException("negative argument " + x.toString() + " of root");
if (n <= 0)
throw new ArithmeticException("negative power " + n + " of root");
if (n == 1)
return x;
/* start the computation from a double precision estimate */
BigDecimal s = new BigDecimal(Math.pow(x.doubleValue(), 1.0 / n));
/*
* this creates nth with nominal precision of 1 digit
*/
final BigDecimal nth = new BigDecimal(n);
/*
* Specify an internal accuracy within the loop which is slightly larger
* than what is demanded by 'eps' below.
*/
final BigDecimal xhighpr = scalePrec(x, 2);
MathContext mc = new MathContext(2 + x.precision());
/*
* Relative accuracy of the result is eps.
*/
final double eps = x.ulp().doubleValue() / (2 * n * x.doubleValue());
for (;;) {
/*
* s = s -(s/n-x/n/s^(n-1)) = s-(s-x/s^(n-1))/n; test correction
* s/n-x/s for being smaller than the precision requested. The
* relative correction is (1-x/s^n)/n,
*/
BigDecimal c = xhighpr.divide(s.pow(n - 1), mc);
c = s.subtract(c);
MathContext locmc = new MathContext(c.precision());
c = c.divide(nth, locmc);
s = s.subtract(c);
if (Math.abs(c.doubleValue() / s.doubleValue()) < eps)
break;
}
return s.round(new MathContext(err2prec(eps)));
} /* BigDecimalMath.root */
static public BigDecimal hypot(final BigDecimal x, final BigDecimal y) {
/*
* compute x^2+y^2
*/
BigDecimal z = x.pow(2).add(y.pow(2));
/*
* truncate to the precision set by x and y. Absolute error =
* 2*x*xerr+2*y*yerr, where the two errors are 1/2 of the ulp's. Two
* intermediate protectio digits.
*/
BigDecimal zerr = x.abs().multiply(x.ulp()).add(y.abs().multiply(y.ulp()));
MathContext mc = new MathContext(2 + err2prec(z, zerr));
/* Pull square root */
z = sqrt(z.round(mc));
/*
* Final rounding. Absolute error in the square root is
* (y*yerr+x*xerr)/z, where zerr holds 2*(x*xerr+y*yerr).
*/
mc = new MathContext(err2prec(z.doubleValue(), 0.5 * zerr.doubleValue() / z.doubleValue()));
return z.round(mc);
} /* BigDecimalMath.hypot */
static public BigDecimal hypot(final int n, final BigDecimal x) {
/*
* compute n^2+x^2 in infinite precision
*/
BigDecimal z = (new BigDecimal(n)).pow(2).add(x.pow(2));
/*
* Truncate to the precision set by x. Absolute error = in z (square of
* the result) is |2*x*xerr|, where the error is 1/2 of the ulp. Two
* intermediate protection digits. zerr is a signed value, but used only
* in conjunction with err2prec(), so this feature does not harm.
*/
double zerr = x.doubleValue() * x.ulp().doubleValue();
MathContext mc = new MathContext(2 + err2prec(z.doubleValue(), zerr));
/* Pull square root */
z = sqrt(z.round(mc));
/*
* Final rounding. Absolute error in the square root is x*xerr/z, where
* zerr holds 2*x*xerr.
*/
mc = new MathContext(err2prec(z.doubleValue(), 0.5 * zerr / z.doubleValue()));
return z.round(mc);
} /* BigDecimalMath.hypot */
static private int TAYLOR_NTERM = 8;
static public BigDecimal exp(BigDecimal x) {
/*
* To calculate the value if x is negative, use exp(-x) = 1/exp(x)
*/
if (x.compareTo(BigDecimal.ZERO) < 0) {
final BigDecimal invx = exp(x.negate());
/*
* Relative error in inverse of invx is the same as the relative
* errror in invx. This is used to define the precision of the
* result.
*/
MathContext mc = new MathContext(invx.precision());
return BigDecimal.ONE.divide(invx, mc);
} else if (x.compareTo(BigDecimal.ZERO) == 0) {
/*
* recover the valid number of digits from x.ulp(), if x hits the
* zero. The x.precision() is 1 then, and does not provide this
* information.
*/
return scalePrec(BigDecimal.ONE, -(int) (Math.log10(x.ulp().doubleValue())));
} else {
/*
* Push the number in the Taylor expansion down to a small value
* where TAYLOR_NTERM terms will do. If x<1, the n-th term is of the
* order x^n/n!, and equal to both the absolute and relative error
* of the result since the result is close to 1. The x.ulp() sets
* the relative and absolute error of the result, as estimated from
* the first Taylor term. We want x^TAYLOR_NTERM/TAYLOR_NTERM! <
* x.ulp, which is guaranteed if x^TAYLOR_NTERM <
* TAYLOR_NTERM*(TAYLOR_NTERM-1)*...*x.ulp.
*/
final double xDbl = x.doubleValue();
final double xUlpDbl = x.ulp().doubleValue();
if (Math.pow(xDbl, TAYLOR_NTERM) < TAYLOR_NTERM * (TAYLOR_NTERM - 1.0)
* (TAYLOR_NTERM - 2.0) * xUlpDbl) {
/*
* Add TAYLOR_NTERM terms of the Taylor expansion (Euler's sum
* formula)
*/
BigDecimal resul = BigDecimal.ONE;
/* x^i */
BigDecimal xpowi = BigDecimal.ONE;
/* i factorial */
BigInteger ifac = BigInteger.ONE;
/*
* TAYLOR_NTERM terms to be added means we move x.ulp() to the
* right for each power of 10 in TAYLOR_NTERM, so the addition
* won't add noise beyond what's already in x.
*/
MathContext mcTay = new MathContext(err2prec(1., xUlpDbl / TAYLOR_NTERM));
for (int i = 1; i <= TAYLOR_NTERM; i++) {
ifac = ifac.multiply(new BigInteger("" + i));
xpowi = xpowi.multiply(x);
final BigDecimal c = xpowi.divide(new BigDecimal(ifac), mcTay);
resul = resul.add(c);
if (Math.abs(xpowi.doubleValue()) < i
&& Math.abs(c.doubleValue()) < 0.5 * xUlpDbl)
break;
}
/*
* exp(x+deltax) = exp(x)(1+deltax) if deltax is <<1. So the
* relative error in the result equals the absolute error in the
* argument.
*/
MathContext mc = new MathContext(err2prec(xUlpDbl / 2.));
return resul.round(mc);
} else {
/*
* Compute exp(x) = (exp(0.1*x))^10. Division by 10 does not
* lead to loss of accuracy.
*/
int exSc = (int) (1.0
- Math.log10(TAYLOR_NTERM * (TAYLOR_NTERM - 1.0) * (TAYLOR_NTERM - 2.0)
* xUlpDbl / Math.pow(xDbl, TAYLOR_NTERM)) / (TAYLOR_NTERM - 1.0));
BigDecimal xby10 = x.scaleByPowerOfTen(-exSc);
BigDecimal expxby10 = exp(xby10);
/*
* Final powering by 10 means that the relative error of the
* result is 10 times the relative error of the base (First
* order binomial expansion). This looses one digit.
*/
MathContext mc = new MathContext(expxby10.precision() - exSc);
/*
* Rescaling the powers of 10 is done in chunks of a maximum of
* 8 to avoid an invalid operation response by the
* BigDecimal.pow library or integer overflow.
*/
while (exSc > 0) {
int exsub = Math.min(8, exSc);
exSc -= exsub;
MathContext mctmp = new MathContext(expxby10.precision() - exsub + 2);
int pex = 1;
while (exsub-- > 0)
pex *= 10;
expxby10 = expxby10.pow(pex, mctmp);
}
return expxby10.round(mc);
}
}
} /* BigDecimalMath.exp */
static public BigDecimal exp(final MathContext mc) {
/* look it up if possible */
if (mc.getPrecision() < E.precision())
return E.round(mc);
else {
/*
* Instantiate a 1.0 with the requested pseudo-accuracy and delegate
* the computation to the public method above.
*/
BigDecimal uni = scalePrec(BigDecimal.ONE, mc.getPrecision());
return exp(uni);
}
} /* BigDecimalMath.exp */
static public BigDecimal log(BigDecimal x) {
/*
* the value is undefined if x is negative.
*/
if (x.compareTo(BigDecimal.ZERO) < 0)
throw new ArithmeticException("Cannot take log of negative " + x.toString());
else if (x.compareTo(BigDecimal.ONE) == 0) {
/* log 1. = 0. */
return scalePrec(BigDecimal.ZERO, x.precision() - 1);
} else if (Math.abs(x.doubleValue() - 1.0) <= 0.3) {
/*
* The standard Taylor series around x=1, z=0, z=x-1.
* Abramowitz-Stegun 4.124. The absolute error is err(z)/(1+z) =
* err(x)/x.
*/
BigDecimal z = scalePrec(x.subtract(BigDecimal.ONE), 2);
BigDecimal zpown = z;
double eps = 0.5 * x.ulp().doubleValue() / Math.abs(x.doubleValue());
BigDecimal resul = z;
for (int k = 2;; k++) {
zpown = multiplyRound(zpown, z);
BigDecimal c = divideRound(zpown, k);
if (k % 2 == 0)
resul = resul.subtract(c);
else
resul = resul.add(c);
if (Math.abs(c.doubleValue()) < eps)
break;
}
MathContext mc = new MathContext(err2prec(resul.doubleValue(), eps));
return resul.round(mc);
} else {
final double xDbl = x.doubleValue();
final double xUlpDbl = x.ulp().doubleValue();
/*
* Map log(x) = log root[r](x)^r = r*log( root[r](x)) with the aim
* to move roor[r](x) near to 1.2 (that is, below the 0.3 appearing
* above), where log(1.2) is roughly 0.2.
*/
int r = (int) (Math.log(xDbl) / 0.2);
/*
* Since the actual requirement is a function of the value 0.3
* appearing above, we avoid the hypothetical case of endless
* recurrence by ensuring that r >= 2.
*/
r = Math.max(2, r);
/*
* Compute r-th root with 2 additional digits of precision
*/
BigDecimal xhighpr = scalePrec(x, 2);
BigDecimal resul = root(r, xhighpr);
resul = log(resul).multiply(new BigDecimal(r));
/*
* error propagation: log(x+errx) = log(x)+errx/x, so the absolute
* error in the result equals the relative error in the input,
* xUlpDbl/xDbl .
*/
MathContext mc = new MathContext(err2prec(resul.doubleValue(), xUlpDbl / xDbl));
return resul.round(mc);
}
} /* BigDecimalMath.log */
static public BigDecimal log(int n, final MathContext mc) {
/*
* the value is undefined if x is negative.
*/
if (n <= 0)
throw new ArithmeticException("Cannot take log of negative " + n);
else if (n == 1)
return BigDecimal.ZERO;
else if (n == 2) {
if (mc.getPrecision() < LOG2.precision())
return LOG2.round(mc);
else {
/*
* Broadhurst arXiv:math/9803067 Error propagation: the error in log(2) is twice the error
* in S(2,-5,...).
*/
int[] a = { 2, -5, -2, -7, -2, -5, 2, -3 };
BigDecimal S = broadhurstBBP(2, 1, a, new MathContext(1 + mc.getPrecision()));
S = S.multiply(new BigDecimal(8));
S = sqrt(divideRound(S, 3));
return S.round(mc);
}
} else if (n == 3) {
/*
* summation of a series roughly proportional to (7/500)^k. Estimate
* count of terms to estimate the precision (drop the favorable
* additional 1/k here): 0.013^k <= 10^(-precision), so
* k*log10(0.013) <= -precision so k>= precision/1.87.
*/
int kmax = (int) (mc.getPrecision() / 1.87);
MathContext mcloc = new MathContext(
mc.getPrecision() + 1 + (int) (Math.log10(kmax * 0.693 / 1.098)));
BigDecimal log3 = multiplyRound(log(2, mcloc), 19);
/*
* log3 is roughly 1, so absolute and relative error are the same.
* The result will be divided by 12, so a conservative error is the
* one already found in mc
*/
double eps = prec2err(1.098, mc.getPrecision()) / kmax;
Rational r = new Rational(7153, 524288);
Rational pk = new Rational(7153, 524288);
for (int k = 1;; k++) {
Rational tmp = pk.divide(k);
if (tmp.doubleValue() < eps)
break;
/*
* how many digits of tmp do we need in the sum?
*/
mcloc = new MathContext(err2prec(tmp.doubleValue(), eps));
BigDecimal c = pk.divide(k).BigDecimalValue(mcloc);
if (k % 2 != 0)
log3 = log3.add(c);
else
log3 = log3.subtract(c);
pk = pk.multiply(r);
}
log3 = divideRound(log3, 12);
return log3.round(mc);
} else if (n == 5) {
/*
* summation of a series roughly proportional to (7/160)^k. Estimate
* count of terms to estimate the precision (drop the favorable
* additional 1/k here): 0.046^k <= 10^(-precision), so
* k*log10(0.046) <= -precision so k>= precision/1.33.
*/
int kmax = (int) (mc.getPrecision() / 1.33);
MathContext mcloc = new MathContext(
mc.getPrecision() + 1 + (int) (Math.log10(kmax * 0.693 / 1.609)));
BigDecimal log5 = multiplyRound(log(2, mcloc), 14);
/*
* log5 is roughly 1.6, so absolute and relative error are the same.
* The result will be divided by 6, so a conservative error is the
* one already found in mc
*/
double eps = prec2err(1.6, mc.getPrecision()) / kmax;
Rational r = new Rational(759, 16384);
Rational pk = new Rational(759, 16384);
for (int k = 1;; k++) {
Rational tmp = pk.divide(k);
if (tmp.doubleValue() < eps)
break;
/*
* how many digits of tmp do we need in the sum?
*/
mcloc = new MathContext(err2prec(tmp.doubleValue(), eps));
BigDecimal c = pk.divide(k).BigDecimalValue(mcloc);
log5 = log5.subtract(c);
pk = pk.multiply(r);
}
log5 = divideRound(log5, 6);
return log5.round(mc);
} else if (n == 7) {
/*
* summation of a series roughly proportional to (1/8)^k. Estimate
* count of terms to estimate the precision (drop the favorable
* additional 1/k here): 0.125^k <= 10^(-precision), so
* k*log10(0.125) <= -precision so k>= precision/0.903.
*/
int kmax = (int) (mc.getPrecision() / 0.903);
MathContext mcloc = new MathContext(
mc.getPrecision() + 1 + (int) (Math.log10(kmax * 3 * 0.693 / 1.098)));
BigDecimal log7 = multiplyRound(log(2, mcloc), 3);
/*
* log7 is roughly 1.9, so absolute and relative error are the same.
*/
double eps = prec2err(1.9, mc.getPrecision()) / kmax;
Rational r = new Rational(1, 8);
Rational pk = new Rational(1, 8);
for (int k = 1;; k++) {
Rational tmp = pk.divide(k);
if (tmp.doubleValue() < eps)
break;
/*
* how many digits of tmp do we need in the sum?
*/
mcloc = new MathContext(err2prec(tmp.doubleValue(), eps));
BigDecimal c = pk.divide(k).BigDecimalValue(mcloc);
log7 = log7.subtract(c);
pk = pk.multiply(r);
}
return log7.round(mc);
}
else {
/*
* At this point one could either forward to the log(BigDecimal)
* signature (implemented) or decompose n into Ifactors and use an
* implemenation of all the prime bases. Estimate of the result;
* convert the mc argument to an absolute error eps log(n+errn) =
* log(n)+errn/n = log(n)+eps
*/
double res = Math.log((double) n);
double eps = prec2err(res, mc.getPrecision());
/*
* errn = eps*n, convert absolute error in result to requirement on
* absolute error in input
*/
eps *= n;
/*
* Convert this absolute requirement of error in n to a relative
* error in n
*/
final MathContext mcloc = new MathContext(1 + err2prec((double) n, eps));
/*
* Padd n with a number of zeros to trigger the required accuracy in
* the standard signature method
*/
BigDecimal nb = scalePrec(new BigDecimal(n), mcloc);
return log(nb);
}
} /* log */
static public BigDecimal log(final Rational r, final MathContext mc) {
/*
* the value is undefined if x is negative.
*/
if (r.compareTo(Rational.ZERO) <= 0)
throw new ArithmeticException("Cannot take log of negative " + r.toString());
else if (r.compareTo(Rational.ONE) == 0)
return BigDecimal.ZERO;
else {
/*
* log(r+epsr) = log(r)+epsr/r. Convert the precision to an absolute
* error in the result. eps contains the required absolute error of
* the result, epsr/r.
*/
double eps = prec2err(Math.log(r.doubleValue()), mc.getPrecision());
/*
* Convert this further into a requirement of the relative precision
* in r, given that epsr/r is also the relative precision of r. Add
* one safety digit.
*/
MathContext mcloc = new MathContext(1 + err2prec(eps));
final BigDecimal resul = log(r.BigDecimalValue(mcloc));
return resul.round(mc);
}
} /* log */
static public BigDecimal pow(final BigDecimal x, final BigDecimal y) {
if (x.compareTo(BigDecimal.ZERO) < 0)
throw new ArithmeticException("Cannot power negative " + x.toString());
else if (x.compareTo(BigDecimal.ZERO) == 0)
return BigDecimal.ZERO;
else {
/*
* return x^y = exp(y*log(x)) ;
*/
BigDecimal logx = log(x);
BigDecimal ylogx = y.multiply(logx);
BigDecimal resul = exp(ylogx);
/*
* The estimation of the relative error in the result is
* |log(x)*err(y)|+|y*err(x)/x|
*/
double errR = Math.abs(logx.doubleValue() * y.ulp().doubleValue() / 2.)
+ Math.abs(y.doubleValue() * x.ulp().doubleValue() / 2. / x.doubleValue());
MathContext mcR = new MathContext(err2prec(1.0, errR));
return resul.round(mcR);
}
} /* BigDecimalMath.pow */
static public BigDecimal powRound(final BigDecimal x, final int n) {
if (n == 1)
return x;
else if (n == 0)
return BigDecimal.ONE;
else {
/*
* The relative error in the result is n times the relative error in
* the input. The estimation is slightly optimistic due to the
* integer rounding of the logarithm. Since the standard
* BigDecimal.pow can only handle positive n, we split the
* algorithm.
*/
MathContext mc = new MathContext(
x.precision() - (int) Math.log10((double) (Math.abs(n))));
if (n > 0)
return x.pow(n, mc);
else
return BigDecimal.ONE.divide(x.pow(-n), mc);
}
} /* BigDecimalMath.powRound */
static public BigDecimal powRound(final BigDecimal x, final BigInteger n) {
if (n.compareTo(Rational.MAX_INT) > 0 || n.compareTo(Rational.MIN_INT) < 0)
throw new ProviderException("Not implemented: big power " + n.toString());
else
return powRound(x, n.intValue());
} /* BigDecimalMath.powRound */
static public BigDecimal powRound(final BigDecimal x, final Rational q) {
if (q.compareTo(BigInteger.ONE) == 0)
return x;
else if (q.signum() == 0)
return BigDecimal.ONE;
else if (q.isInteger()) {
/*
* We are sure that the denominator is positive here, because
* normalize() has been called during constrution etc.
*/
return powRound(x, q.a);
}
/*
* Refuse to operate on the general negative basis. The integer q have
* already been handled above.
*/
else if (x.compareTo(BigDecimal.ZERO) < 0)
throw new ArithmeticException("Cannot power negative " + x.toString());
else {
if (q.isIntegerFrac()) {
/*
* Newton method with first estimate in double precision. The
* disadvantage of this first line here is that the result must
* fit in the standard range of double precision numbers
* exponents.
*/
double estim = Math.pow(x.doubleValue(), q.doubleValue());
BigDecimal res = new BigDecimal(estim);
/*
* The error in x^q is q*x^(q-1)*Delta(x). The relative error is
* q*Delta(x)/x, q times the relative error of x.
*/
BigDecimal reserr = new BigDecimal(0.5 * q.abs().doubleValue()
* x.ulp().divide(x.abs(), MathContext.DECIMAL64).doubleValue());
/*
* The main point in branching the cases above is that this
* conversion will succeed for numerator and denominator of q.
*/
int qa = q.a.intValue();
int qb = q.b.intValue();
/* Newton iterations. */
BigDecimal xpowa = powRound(x, qa);
for (;;) {
/*
* numerator and denominator of the Newton term. The major
* disadvantage of this implementation is that the updates
* of the powers of the new estimate are done in full
* precision calling BigDecimal.pow(), which becomes slow if
* the denominator of q is large.
*/
BigDecimal nu = res.pow(qb).subtract(xpowa);
BigDecimal de = multiplyRound(res.pow(qb - 1), q.b);
/* estimated correction */
BigDecimal eps = nu.divide(de, MathContext.DECIMAL64);
BigDecimal err = res.multiply(reserr, MathContext.DECIMAL64);
int precDiv = 2 + err2prec(eps, err);
if (precDiv <= 0) {
/*
* The case when the precision is already reached and
* any precision will do.
*/
eps = nu.divide(de, MathContext.DECIMAL32);
} else {
MathContext mc = new MathContext(precDiv);
eps = nu.divide(de, mc);
}
res = subtractRound(res, eps);
/*
* reached final precision if the relative error fell below
* reserr, |eps/res| < reserr
*/
if (eps.divide(res, MathContext.DECIMAL64).abs().compareTo(reserr) < 0) {
/*
* delete the bits of extra precision kept in this
* working copy.
*/
MathContext mc = new MathContext(err2prec(reserr.doubleValue()));
return res.round(mc);
}
}
} else {
/*
* The error in x^q is q*x^(q-1)*Delta(x) + Delta(q)*x^q*log(x).
* The relative error is q/x*Delta(x) + Delta(q)*log(x). Convert
* q to a floating point number such that its relative error
* becomes negligible: Delta(q)/q << Delta(x)/x/log(x) .
*/
int precq = 3 + err2prec((x.ulp().divide(x, MathContext.DECIMAL64)).doubleValue()
/ Math.log(x.doubleValue()));
MathContext mc = new MathContext(precq);
/*
* Perform the actual calculation as exponentiation of two
* floating point numbers.
*/
return pow(x, q.BigDecimalValue(mc));
}
}
} /* BigDecimalMath.powRound */
static public BigDecimal sin(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) < 0)
return sin(x.negate()).negate();
else if (x.compareTo(BigDecimal.ZERO) == 0)
return BigDecimal.ZERO;
else {
/*
* reduce modulo 2pi
*/
BigDecimal res = mod2pi(x);
double errpi = 0.5 * Math.abs(x.ulp().doubleValue());
MathContext mc = new MathContext(2 + err2prec(3.14159, errpi));
BigDecimal p = pi(mc);
mc = new MathContext(x.precision());
if (res.compareTo(p) > 0) {
/*
* pi 0) {
/*
* pi/2 0) {
/*
* x>pi/4: sin(x) = cos(pi/2-x)
*/
return cos(subtractRound(p.divide(new BigDecimal("2")), res));
} else {
/*
* Simple Taylor expansion, sum_{i=1..infinity}
* (-1)^(..)res^(2i+1)/(2i+1)!
*/
BigDecimal resul = res;
/* x^i */
BigDecimal xpowi = res;
/* 2i+1 factorial */
BigInteger ifac = BigInteger.ONE;
/*
* The error in the result is set by the error in x itself.
*/
double xUlpDbl = res.ulp().doubleValue();
/*
* The error in the result is set by the error in x itself.
* We need at most k terms to squeeze x^(2k+1)/(2k+1)! below
* this value. x^(2k+1) < x.ulp; (2k+1)*log10(x) <
* -x.precision; 2k*log10(x)< -x.precision; 2k*(-log10(x)) >
* x.precision; 2k*log10(1/x) > x.precision
*/
int k = (int) (res.precision() / Math.log10(1.0 / res.doubleValue())) / 2;
MathContext mcTay = new MathContext(err2prec(res.doubleValue(), xUlpDbl / k));
for (int i = 1;; i++) {
/*
* TBD: at which precision will 2*i or 2*i+1 overflow?
*/
ifac = ifac.multiply(new BigInteger("" + (2 * i)));
ifac = ifac.multiply(new BigInteger("" + (2 * i + 1)));
xpowi = xpowi.multiply(res).multiply(res).negate();
BigDecimal corr = xpowi.divide(new BigDecimal(ifac), mcTay);
resul = resul.add(corr);
if (corr.abs().doubleValue() < 0.5 * xUlpDbl)
break;
}
/*
* The error in the result is set by the error in x itself.
*/
mc = new MathContext(res.precision());
return resul.round(mc);
}
}
}
} /* sin */
static public BigDecimal cos(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) < 0)
return cos(x.negate());
else if (x.compareTo(BigDecimal.ZERO) == 0)
return BigDecimal.ONE;
else {
/*
* reduce modulo 2pi
*/
BigDecimal res = mod2pi(x);
double errpi = 0.5 * Math.abs(x.ulp().doubleValue());
MathContext mc = new MathContext(2 + err2prec(3.14159, errpi));
BigDecimal p = pi(mc);
mc = new MathContext(x.precision());
if (res.compareTo(p) > 0) {
/*
* pi 0) {
/*
* pi/2 0) {
/*
* x>pi/4: cos(x) = sin(pi/2-x)
*/
return sin(subtractRound(p.divide(new BigDecimal("2")), res));
} else {
/*
* Simple Taylor expansion, sum_{i=0..infinity}
* (-1)^(..)res^(2i)/(2i)!
*/
BigDecimal resul = BigDecimal.ONE;
/* x^i */
BigDecimal xpowi = BigDecimal.ONE;
/* 2i factorial */
BigInteger ifac = BigInteger.ONE;
/*
* The absolute error in the result is the error in x^2/2
* which is x times the error in x.
*/
double xUlpDbl = 0.5 * res.ulp().doubleValue() * res.doubleValue();
/*
* The error in the result is set by the error in x^2/2
* itself, xUlpDbl. We need at most k terms to push
* x^(2k+1)/(2k+1)! below this value. x^(2k) < xUlpDbl;
* (2k)*log(x) < log(xUlpDbl);
*/
int k = (int) (Math.log(xUlpDbl) / Math.log(res.doubleValue())) / 2;
MathContext mcTay = new MathContext(err2prec(1., xUlpDbl / k));
for (int i = 1;; i++) {
/*
* TBD: at which precision will 2*i-1 or 2*i overflow?
*/
ifac = ifac.multiply(new BigInteger("" + (2 * i - 1)));
ifac = ifac.multiply(new BigInteger("" + (2 * i)));
xpowi = xpowi.multiply(res).multiply(res).negate();
BigDecimal corr = xpowi.divide(new BigDecimal(ifac), mcTay);
resul = resul.add(corr);
if (corr.abs().doubleValue() < 0.5 * xUlpDbl)
break;
}
/*
* The error in the result is governed by the error in x
* itself.
*/
mc = new MathContext(err2prec(resul.doubleValue(), xUlpDbl));
return resul.round(mc);
}
}
}
} /* BigDecimalMath.cos */
static public BigDecimal tan(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) == 0)
return BigDecimal.ZERO;
else if (x.compareTo(BigDecimal.ZERO) < 0) {
return tan(x.negate()).negate();
} else {
/*
* reduce modulo pi
*/
BigDecimal res = modpi(x);
/*
* absolute error in the result is err(x)/cos^2(x) to lowest order
*/
final double xDbl = res.doubleValue();
final double xUlpDbl = x.ulp().doubleValue() / 2.;
final double eps = xUlpDbl / 2. / Math.pow(Math.cos(xDbl), 2.);
if (xDbl > 0.8) {
/* tan(x) = 1/cot(x) */
BigDecimal co = cot(x);
MathContext mc = new MathContext(err2prec(1. / co.doubleValue(), eps));
return BigDecimal.ONE.divide(co, mc);
} else {
final BigDecimal xhighpr = scalePrec(res, 2);
final BigDecimal xhighprSq = multiplyRound(xhighpr, xhighpr);
BigDecimal resul = xhighpr.plus();
/* x^(2i+1) */
BigDecimal xpowi = xhighpr;
Bernoulli b = new Bernoulli();
/* 2^(2i) */
BigInteger fourn = new BigInteger("4");
/* (2i)! */
BigInteger fac = new BigInteger("2");
for (int i = 2;; i++) {
Rational f = b.at(2 * i).abs();
fourn = fourn.shiftLeft(2);
fac = fac.multiply(new BigInteger("" + (2 * i)))
.multiply(new BigInteger("" + (2 * i - 1)));
f = f.multiply(fourn).multiply(fourn.subtract(BigInteger.ONE)).divide(fac);
xpowi = multiplyRound(xpowi, xhighprSq);
BigDecimal c = multiplyRound(xpowi, f);
resul = resul.add(c);
if (Math.abs(c.doubleValue()) < 0.1 * eps)
break;
}
MathContext mc = new MathContext(err2prec(resul.doubleValue(), eps));
return resul.round(mc);
}
}
} /* BigDecimalMath.tan */
static public BigDecimal cot(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) == 0) {
throw new ArithmeticException("Cannot take cot of zero " + x.toString());
} else if (x.compareTo(BigDecimal.ZERO) < 0) {
return cot(x.negate()).negate();
} else {
/*
* reduce modulo pi
*/
BigDecimal res = modpi(x);
/*
* absolute error in the result is err(x)/sin^2(x) to lowest order
*/
final double xDbl = res.doubleValue();
final double xUlpDbl = x.ulp().doubleValue() / 2.;
final double eps = xUlpDbl / 2. / Math.pow(Math.sin(xDbl), 2.);
final BigDecimal xhighpr = scalePrec(res, 2);
final BigDecimal xhighprSq = multiplyRound(xhighpr, xhighpr);
MathContext mc = new MathContext(err2prec(xhighpr.doubleValue(), eps));
BigDecimal resul = BigDecimal.ONE.divide(xhighpr, mc);
/* x^(2i-1) */
BigDecimal xpowi = xhighpr;
Bernoulli b = new Bernoulli();
/* 2^(2i) */
BigInteger fourn = new BigInteger("4");
/* (2i)! */
BigInteger fac = BigInteger.ONE;
for (int i = 1;; i++) {
Rational f = b.at(2 * i);
fac = fac.multiply(new BigInteger("" + (2 * i)))
.multiply(new BigInteger("" + (2 * i - 1)));
f = f.multiply(fourn).divide(fac);
BigDecimal c = multiplyRound(xpowi, f);
if (i % 2 == 0)
resul = resul.add(c);
else
resul = resul.subtract(c);
if (Math.abs(c.doubleValue()) < 0.1 * eps)
break;
fourn = fourn.shiftLeft(2);
xpowi = multiplyRound(xpowi, xhighprSq);
}
mc = new MathContext(err2prec(resul.doubleValue(), eps));
return resul.round(mc);
}
} /* BigDecimalMath.cot */
static public BigDecimal asin(final BigDecimal x) {
if (x.compareTo(BigDecimal.ONE) > 0 || x.compareTo(BigDecimal.ONE.negate()) < 0) {
throw new ArithmeticException("Out of range argument " + x.toString() + " of asin");
} else if (x.compareTo(BigDecimal.ZERO) == 0)
return BigDecimal.ZERO;
else if (x.compareTo(BigDecimal.ONE) == 0) {
/*
* arcsin(1) = pi/2
*/
double errpi = Math.sqrt(x.ulp().doubleValue());
MathContext mc = new MathContext(err2prec(3.14159, errpi));
return pi(mc).divide(new BigDecimal(2));
} else if (x.compareTo(BigDecimal.ZERO) < 0) {
return asin(x.negate()).negate();
} else if (x.doubleValue() > 0.7) {
final BigDecimal xCompl = BigDecimal.ONE.subtract(x);
final double xDbl = x.doubleValue();
final double xUlpDbl = x.ulp().doubleValue() / 2.;
final double eps = xUlpDbl / 2. / Math.sqrt(1. - Math.pow(xDbl, 2.));
final BigDecimal xhighpr = scalePrec(xCompl, 3);
final BigDecimal xhighprV = divideRound(xhighpr, 4);
BigDecimal resul = BigDecimal.ONE;
/* x^(2i+1) */
BigDecimal xpowi = BigDecimal.ONE;
/* i factorial */
BigInteger ifacN = BigInteger.ONE;
BigInteger ifacD = BigInteger.ONE;
for (int i = 1;; i++) {
ifacN = ifacN.multiply(new BigInteger("" + (2 * i - 1)));
ifacD = ifacD.multiply(new BigInteger("" + i));
if (i == 1)
xpowi = xhighprV;
else
xpowi = multiplyRound(xpowi, xhighprV);
BigDecimal c = divideRound(multiplyRound(xpowi, ifacN),
ifacD.multiply(new BigInteger("" + (2 * i + 1))));
resul = resul.add(c);
/*
* series started 1+x/12+... which yields an estimate of the
* sum's error
*/
if (Math.abs(c.doubleValue()) < xUlpDbl / 120.)
break;
}
/*
* sqrt(2*z)*(1+...)
*/
xpowi = sqrt(xhighpr.multiply(new BigDecimal(2)));
resul = multiplyRound(xpowi, resul);
MathContext mc = new MathContext(resul.precision());
BigDecimal pihalf = pi(mc).divide(new BigDecimal(2));
mc = new MathContext(err2prec(resul.doubleValue(), eps));
return pihalf.subtract(resul, mc);
} else {
/*
* absolute error in the result is err(x)/sqrt(1-x^2) to lowest
* order
*/
final double xDbl = x.doubleValue();
final double xUlpDbl = x.ulp().doubleValue() / 2.;
final double eps = xUlpDbl / 2. / Math.sqrt(1. - Math.pow(xDbl, 2.));
final BigDecimal xhighpr = scalePrec(x, 2);
final BigDecimal xhighprSq = multiplyRound(xhighpr, xhighpr);
BigDecimal resul = xhighpr.plus();
/* x^(2i+1) */
BigDecimal xpowi = xhighpr;
/* i factorial */
BigInteger ifacN = BigInteger.ONE;
BigInteger ifacD = BigInteger.ONE;
for (int i = 1;; i++) {
ifacN = ifacN.multiply(new BigInteger("" + (2 * i - 1)));
ifacD = ifacD.multiply(new BigInteger("" + (2 * i)));
xpowi = multiplyRound(xpowi, xhighprSq);
BigDecimal c = divideRound(multiplyRound(xpowi, ifacN),
ifacD.multiply(new BigInteger("" + (2 * i + 1))));
resul = resul.add(c);
if (Math.abs(c.doubleValue()) < 0.1 * eps)
break;
}
MathContext mc = new MathContext(err2prec(resul.doubleValue(), eps));
return resul.round(mc);
}
} /* BigDecimalMath.asin */
static public BigDecimal acos(final BigDecimal x) {
/*
* Essentially forwarded to pi/2 - asin(x)
*/
final BigDecimal xhighpr = scalePrec(x, 2);
BigDecimal resul = asin(xhighpr);
double eps = resul.ulp().doubleValue() / 2.;
MathContext mc = new MathContext(err2prec(3.14159, eps));
BigDecimal pihalf = pi(mc).divide(new BigDecimal(2));
resul = pihalf.subtract(resul);
/*
* absolute error in the result is err(x)/sqrt(1-x^2) to lowest order
*/
final double xDbl = x.doubleValue();
final double xUlpDbl = x.ulp().doubleValue() / 2.;
eps = xUlpDbl / 2. / Math.sqrt(1. - Math.pow(xDbl, 2.));
mc = new MathContext(err2prec(resul.doubleValue(), eps));
return resul.round(mc);
} /* BigDecimalMath.acos */
static public BigDecimal atan(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) < 0) {
return atan(x.negate()).negate();
} else if (x.compareTo(BigDecimal.ZERO) == 0)
return BigDecimal.ZERO;
else if (x.doubleValue() > 0.7 && x.doubleValue() < 3.0) {
/*
* Abramowitz-Stegun 4.4.34 convergence acceleration 2*arctan(x) =
* arctan(2x/(1-x^2)) = arctan(y). x=(sqrt(1+y^2)-1)/y This maps
* 0<=y<=3 to 0<=x<=0.73 roughly. Temporarily with 2 protectionist
* digits.
*/
BigDecimal y = scalePrec(x, 2);
BigDecimal newx = divideRound(hypot(1, y).subtract(BigDecimal.ONE), y);
/* intermediate result with too optimistic error estimate */
BigDecimal resul = multiplyRound(atan(newx), 2);
/*
* absolute error in the result is errx/(1+x^2), where errx = half
* of the ulp.
*/
double eps = x.ulp().doubleValue() / (2.0 * Math.hypot(1.0, x.doubleValue()));
MathContext mc = new MathContext(err2prec(resul.doubleValue(), eps));
return resul.round(mc);
} else if (x.doubleValue() < 0.71) {
/* Taylor expansion around x=0; Abramowitz-Stegun 4.4.42 */
final BigDecimal xhighpr = scalePrec(x, 2);
final BigDecimal xhighprSq = multiplyRound(xhighpr, xhighpr).negate();
BigDecimal resul = xhighpr.plus();
/* signed x^(2i+1) */
BigDecimal xpowi = xhighpr;
/*
* absolute error in the result is errx/(1+x^2), where errx = half
* of the ulp.
*/
double eps = x.ulp().doubleValue() / (2.0 * Math.hypot(1.0, x.doubleValue()));
for (int i = 1;; i++) {
xpowi = multiplyRound(xpowi, xhighprSq);
BigDecimal c = divideRound(xpowi, 2 * i + 1);
resul = resul.add(c);
if (Math.abs(c.doubleValue()) < 0.1 * eps)
break;
}
MathContext mc = new MathContext(err2prec(resul.doubleValue(), eps));
return resul.round(mc);
} else {
/* Taylor expansion around x=infinity; Abramowitz-Stegun 4.4.42 */
/*
* absolute error in the result is errx/(1+x^2), where errx = half
* of the ulp.
*/
double eps = x.ulp().doubleValue() / (2.0 * Math.hypot(1.0, x.doubleValue()));
/*
* start with the term pi/2; gather its precision relative to the
* expected result
*/
MathContext mc = new MathContext(2 + err2prec(3.1416, eps));
BigDecimal onepi = pi(mc);
BigDecimal resul = onepi.divide(new BigDecimal(2));
final BigDecimal xhighpr = divideRound(-1, scalePrec(x, 2));
final BigDecimal xhighprSq = multiplyRound(xhighpr, xhighpr).negate();
/* signed x^(2i+1) */
BigDecimal xpowi = xhighpr;
for (int i = 0;; i++) {
BigDecimal c = divideRound(xpowi, 2 * i + 1);
resul = resul.add(c);
if (Math.abs(c.doubleValue()) < 0.1 * eps)
break;
xpowi = multiplyRound(xpowi, xhighprSq);
}
mc = new MathContext(err2prec(resul.doubleValue(), eps));
return resul.round(mc);
}
} /* BigDecimalMath.atan */
static public BigDecimal cosh(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) < 0)
return cos(x.negate());
else if (x.compareTo(BigDecimal.ZERO) == 0)
return BigDecimal.ONE;
else {
if (x.doubleValue() > 1.5) {
/*
* cosh^2(x) = 1+ sinh^2(x).
*/
return hypot(1, sinh(x));
} else {
BigDecimal xhighpr = scalePrec(x, 2);
/* Simple Taylor expansion, sum_{0=1..infinity} x^(2i)/(2i)! */
BigDecimal resul = BigDecimal.ONE;
/* x^i */
BigDecimal xpowi = BigDecimal.ONE;
/* 2i factorial */
BigInteger ifac = BigInteger.ONE;
/*
* The absolute error in the result is the error in x^2/2 which
* is x times the error in x.
*/
double xUlpDbl = 0.5 * x.ulp().doubleValue() * x.doubleValue();
/*
* The error in the result is set by the error in x^2/2 itself,
* xUlpDbl. We need at most k terms to push x^(2k)/(2k)! below
* this value. x^(2k) < xUlpDbl; (2k)*log(x) < log(xUlpDbl);
*/
int k = (int) (Math.log(xUlpDbl) / Math.log(x.doubleValue())) / 2;
/*
* The individual terms are all smaller than 1, so an estimate
* of 1.0 for the absolute value will give a safe relative error
* estimate for the indivdual terms
*/
MathContext mcTay = new MathContext(err2prec(1., xUlpDbl / k));
for (int i = 1;; i++) {
/*
* TBD: at which precision will 2*i-1 or 2*i overflow?
*/
ifac = ifac.multiply(new BigInteger("" + (2 * i - 1)));
ifac = ifac.multiply(new BigInteger("" + (2 * i)));
xpowi = xpowi.multiply(xhighpr).multiply(xhighpr);
BigDecimal corr = xpowi.divide(new BigDecimal(ifac), mcTay);
resul = resul.add(corr);
if (corr.abs().doubleValue() < 0.5 * xUlpDbl)
break;
}
/*
* The error in the result is governed by the error in x itself.
*/
MathContext mc = new MathContext(err2prec(resul.doubleValue(), xUlpDbl));
return resul.round(mc);
}
}
} /* BigDecimalMath.cosh */
static public BigDecimal sinh(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) < 0)
return sinh(x.negate()).negate();
else if (x.compareTo(BigDecimal.ZERO) == 0)
return BigDecimal.ZERO;
else {
if (x.doubleValue() > 2.4) {
/*
* Move closer to zero with sinh(2x)= 2*sinh(x)*cosh(x).
*/
BigDecimal two = new BigDecimal(2);
BigDecimal xhalf = x.divide(two);
BigDecimal resul = sinh(xhalf).multiply(cosh(xhalf)).multiply(two);
/*
* The error in the result is set by the error in x itself. The
* first derivative of sinh(x) is cosh(x), so the absolute error
* in the result is cosh(x)*errx, and the relative error is
* coth(x)*errx = errx/tanh(x)
*/
double eps = Math.tanh(x.doubleValue());
MathContext mc = new MathContext(err2prec(0.5 * x.ulp().doubleValue() / eps));
return resul.round(mc);
} else {
BigDecimal xhighpr = scalePrec(x, 2);
/*
* Simple Taylor expansion, sum_{i=0..infinity} x^(2i+1)/(2i+1)!
*/
BigDecimal resul = xhighpr;
/* x^i */
BigDecimal xpowi = xhighpr;
/* 2i+1 factorial */
BigInteger ifac = BigInteger.ONE;
/*
* The error in the result is set by the error in x itself.
*/
double xUlpDbl = x.ulp().doubleValue();
/*
* The error in the result is set by the error in x itself. We
* need at most k terms to squeeze x^(2k+1)/(2k+1)! below this
* value. x^(2k+1) < x.ulp; (2k+1)*log10(x) < -x.precision;
* 2k*log10(x)< -x.precision; 2k*(-log10(x)) > x.precision;
* 2k*log10(1/x) > x.precision
*/
int k = (int) (x.precision() / Math.log10(1.0 / xhighpr.doubleValue())) / 2;
MathContext mcTay = new MathContext(err2prec(x.doubleValue(), xUlpDbl / k));
for (int i = 1;; i++) {
/*
* TBD: at which precision will 2*i or 2*i+1 overflow?
*/
ifac = ifac.multiply(new BigInteger("" + (2 * i)));
ifac = ifac.multiply(new BigInteger("" + (2 * i + 1)));
xpowi = xpowi.multiply(xhighpr).multiply(xhighpr);
BigDecimal corr = xpowi.divide(new BigDecimal(ifac), mcTay);
resul = resul.add(corr);
if (corr.abs().doubleValue() < 0.5 * xUlpDbl)
break;
}
/*
* The error in the result is set by the error in x itself.
*/
MathContext mc = new MathContext(x.precision());
return resul.round(mc);
}
}
} /* BigDecimalMath.sinh */
static public BigDecimal tanh(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) < 0)
return tanh(x.negate()).negate();
else if (x.compareTo(BigDecimal.ZERO) == 0)
return BigDecimal.ZERO;
else {
BigDecimal xhighpr = scalePrec(x, 2);
/*
* tanh(x) = (1-e^(-2x))/(1+e^(-2x)) .
*/
BigDecimal exp2x = exp(xhighpr.multiply(new BigDecimal(-2)));
/*
* The error in tanh x is err(x)/cosh^2(x).
*/
double eps = 0.5 * x.ulp().doubleValue() / Math.pow(Math.cosh(x.doubleValue()), 2.0);
MathContext mc = new MathContext(err2prec(Math.tanh(x.doubleValue()), eps));
return BigDecimal.ONE.subtract(exp2x).divide(BigDecimal.ONE.add(exp2x), mc);
}
} /* BigDecimalMath.tanh */
static public BigDecimal asinh(final BigDecimal x) {
if (x.compareTo(BigDecimal.ZERO) == 0)
return BigDecimal.ZERO;
else {
BigDecimal xhighpr = scalePrec(x, 2);
/*
* arcsinh(x) = log(x+hypot(1,x))
*/
BigDecimal logx = log(hypot(1, xhighpr).add(xhighpr));
/*
* The absolute error in arcsinh x is err(x)/sqrt(1+x^2)
*/
double xDbl = x.doubleValue();
double eps = 0.5 * x.ulp().doubleValue() / Math.hypot(1., xDbl);
MathContext mc = new MathContext(err2prec(logx.doubleValue(), eps));
return logx.round(mc);
}
} /* BigDecimalMath.asinh */
static public BigDecimal acosh(final BigDecimal x) {
if (x.compareTo(BigDecimal.ONE) < 0)
throw new ArithmeticException("Out of range argument cosh " + x.toString());
else if (x.compareTo(BigDecimal.ONE) == 0)
return BigDecimal.ZERO;
else {
BigDecimal xhighpr = scalePrec(x, 2);
/*
* arccosh(x) = log(x+sqrt(x^2-1))
*/
BigDecimal logx = log(sqrt(xhighpr.pow(2).subtract(BigDecimal.ONE)).add(xhighpr));
/*
* The absolute error in arcsinh x is err(x)/sqrt(x^2-1)
*/
double xDbl = x.doubleValue();
double eps = 0.5 * x.ulp().doubleValue() / Math.sqrt(xDbl * xDbl - 1.);
MathContext mc = new MathContext(err2prec(logx.doubleValue(), eps));
return logx.round(mc);
}
} /* BigDecimalMath.acosh */
static public BigDecimal Gamma(final BigDecimal x) {
/*
* reduce to interval near 1.0 with the functional relation,
* Abramowitz-Stegun 6.1.33
*/
if (x.compareTo(BigDecimal.ZERO) < 0)
return divideRound(Gamma(x.add(BigDecimal.ONE)), x);
else if (x.doubleValue() > 1.5) {
/*
* Gamma(x) = Gamma(xmin+n) = Gamma(xmin)*Pochhammer(xmin,n).
*/
int n = (int) (x.doubleValue() - 0.5);
BigDecimal xmin1 = x.subtract(new BigDecimal(n));
return multiplyRound(Gamma(xmin1), pochhammer(xmin1, n));
} else {
/*
* apply Abramowitz-Stegun 6.1.33
*/
BigDecimal z = x.subtract(BigDecimal.ONE);
/*
* add intermediately 2 digits to the partial sum accumulation
*/
z = scalePrec(z, 2);
MathContext mcloc = new MathContext(z.precision());
/*
* measure of the absolute error is the relative error in the first,
* logarithmic term
*/
double eps = x.ulp().doubleValue() / x.doubleValue();
BigDecimal resul = log(scalePrec(x, 2)).negate();
if (x.compareTo(BigDecimal.ONE) != 0) {
BigDecimal gammCompl = BigDecimal.ONE.subtract(gamma(mcloc));
resul = resul.add(multiplyRound(z, gammCompl));
for (int n = 2;; n++) {
/*
* multiplying z^n/n by zeta(n-1) means that the two
* relative errors add. so the requirement in the relative
* error of zeta(n)-1 is that this is somewhat smaller than
* the relative error in z^n/n (the absolute error of
* thelatter is the absolute error in z)
*/
BigDecimal c = divideRound(z.pow(n, mcloc), n);
MathContext m = new MathContext(
err2prec(n * z.ulp().doubleValue() / 2. / z.doubleValue()));
c = c.round(m);
/*
* At larger n, zeta(n)-1 is roughly 1/2^n. The product is
* c/2^n. The relative error in c is c.ulp/2/c . The error
* in the product should be small versus eps/10. Error from
* 1/2^n is c*err(sigma-1). We need a relative error of
* zeta-1 of the order of c.ulp/50/c. This is an absolute
* error in zeta-1 of c.ulp/50/c/2^n, and also the absolute
* error in zeta, because zeta is of the order of 1.
*/
if (eps / 100. / c.doubleValue() < 0.01)
m = new MathContext(err2prec(eps / 100. / c.doubleValue()));
else
m = new MathContext(2);
/* zeta(n) -1 */
BigDecimal zetm1 = zeta(n, m).subtract(BigDecimal.ONE);
c = multiplyRound(c, zetm1);
if (n % 2 == 0)
resul = resul.add(c);
else
resul = resul.subtract(c);
/*
* alternating sum, so truncating as eps is reached suffices
*/
if (Math.abs(c.doubleValue()) < eps)
break;
}
}
/*
* The relative error in the result is the absolute error in the
* input variable times the digamma (psi) value at that point.
*/
double zdbl = z.doubleValue();
eps = psi(zdbl) * x.ulp().doubleValue() / 2.;
mcloc = new MathContext(err2prec(eps));
return exp(resul).round(mcloc);
}
} /* BigDecimalMath.gamma */
static public BigDecimal Gamma(final Rational q, final MathContext mc) {
if (q.isBigInteger()) {
if (q.compareTo(Rational.ZERO) <= 0)
throw new ArithmeticException("Gamma at " + q.toString());
else {
/* Gamma(n) = (n-1)! */
Factorial f = new Factorial();
BigInteger g = f.at(q.trunc().intValue() - 1);
return scalePrec(new BigDecimal(g), mc);
}
} else if (q.b.intValue() == 2) {
/*
* half integer cases which are related to sqrt(pi)
*/
BigDecimal p = sqrt(pi(mc));
if (q.compareTo(Rational.ZERO) >= 0) {
Rational pro = Rational.ONE;
Rational f = q.subtract(1);
while (f.compareTo(Rational.ZERO) > 0) {
pro = pro.multiply(f);
f = f.subtract(1);
}
return multiplyRound(p, pro);
} else {
Rational pro = Rational.ONE;
Rational f = q;
while (f.compareTo(Rational.ZERO) < 0) {
pro = pro.divide(f);
f = f.add(1);
}
return multiplyRound(p, pro);
}
} else {
/*
* The relative error of the result is psi(x)*Delta(x). Tune
* Delta(x) such that this is equivalent to mc: Delta(x) =
* precision/psi(x).
*/
double qdbl = q.doubleValue();
double deltx = 5. * Math.pow(10., -mc.getPrecision()) / psi(qdbl);
MathContext mcx = new MathContext(err2prec(qdbl, deltx));
BigDecimal x = q.BigDecimalValue(mcx);
/* forward calculation to the general floating point case */
return Gamma(x);
}
} /* BigDecimalMath.Gamma */
static public BigDecimal pochhammer(final BigDecimal x, final int n) {
/*
* reduce to interval near 1.0 with the functional relation,
* Abramowitz-Stegun 6.1.33
*/
if (n < 0)
throw new ProviderException("Not implemented: pochhammer with negative index " + n);
else if (n == 0)
return BigDecimal.ONE;
else {
/*
* internally two safety digits
*/
BigDecimal xhighpr = scalePrec(x, 2);
BigDecimal resul = xhighpr;
double xUlpDbl = x.ulp().doubleValue();
double xDbl = x.doubleValue();
/*
* relative error of the result is the sum of the relative errors of
* the factors
*/
double eps = 0.5 * xUlpDbl / Math.abs(xDbl);
for (int i = 1; i < n; i++) {
eps += 0.5 * xUlpDbl / Math.abs(xDbl + i);
resul = resul.multiply(xhighpr.add(new BigDecimal(i)));
final MathContext mcloc = new MathContext(4 + err2prec(eps));
resul = resul.round(mcloc);
}
return resul.round(new MathContext(err2prec(eps)));
}
} /* BigDecimalMath.pochhammer */
static public BigDecimal mod2pi(BigDecimal x) {
/*
* write x= 2*pi*k+r with the precision in r defined by the precision of
* x and not compromised by the precision of 2*pi, so the ulp of 2*pi*k
* should match the ulp of x. First get a guess of k to figure out how
* many digits of 2*pi are needed.
*/
int k = (int) (0.5 * x.doubleValue() / Math.PI);
/*
* want to have err(2*pi*k)< err(x)=0.5*x.ulp, so err(pi) = err(x)/(4k)
* with two safety digits
*/
double err2pi;
if (k != 0)
err2pi = 0.25 * Math.abs(x.ulp().doubleValue() / k);
else
err2pi = 0.5 * Math.abs(x.ulp().doubleValue());
MathContext mc = new MathContext(2 + err2prec(6.283, err2pi));
BigDecimal twopi = pi(mc).multiply(new BigDecimal(2));
/*
* Delegate the actual operation to the BigDecimal class, which may
* return a negative value of x was negative .
*/
BigDecimal res = x.remainder(twopi);
if (res.compareTo(BigDecimal.ZERO) < 0)
res = res.add(twopi);
/*
* The actual precision is set by the input value, its absolute value of
* x.ulp()/2.
*/
mc = new MathContext(err2prec(res.doubleValue(), x.ulp().doubleValue() / 2.));
return res.round(mc);
} /* mod2pi */
static public BigDecimal modpi(BigDecimal x) {
/*
* write x= pi*k+r with the precision in r defined by the precision of x
* and not compromised by the precision of pi, so the ulp of pi*k should
* match the ulp of x. First get a guess of k to figure out how many
* digits of pi are needed.
*/
int k = (int) (x.doubleValue() / Math.PI);
/*
* want to have err(pi*k)< err(x)=x.ulp/2, so err(pi) = err(x)/(2k) with
* two safety digits
*/
double errpi;
if (k != 0)
errpi = 0.5 * Math.abs(x.ulp().doubleValue() / k);
else
errpi = 0.5 * Math.abs(x.ulp().doubleValue());
MathContext mc = new MathContext(2 + err2prec(3.1416, errpi));
BigDecimal onepi = pi(mc);
BigDecimal pihalf = onepi.divide(new BigDecimal(2));
/*
* Delegate the actual operation to the BigDecimal class, which may
* return a negative value of x was negative .
*/
BigDecimal res = x.remainder(onepi);
if (res.compareTo(pihalf) > 0)
res = res.subtract(onepi);
else if (res.compareTo(pihalf.negate()) < 0)
res = res.add(onepi);
/*
* The actual precision is set by the input value, its absolute value of
* x.ulp()/2.
*/
mc = new MathContext(err2prec(res.doubleValue(), x.ulp().doubleValue() / 2.));
return res.round(mc);
} /* modpi */
static public BigDecimal zeta(final int n, final MathContext mc) {
if (n <= 0)
throw new ProviderException("Not implemented: zeta at negative argument " + n);
if (n == 1)
throw new ArithmeticException("Pole at zeta(1) ");
if (n % 2 == 0) {
/*
* Even indices. Abramowitz-Stegun 23.2.16. Start with
* 2^(n-1)*B(n)/n!
*/
Rational b = (new Bernoulli()).at(n).abs();
b = b.divide((new Factorial()).at(n));
b = b.multiply(BigInteger.ONE.shiftLeft(n - 1));
/*
* to be multiplied by pi^n. Absolute error in the result of pi^n is
* n times error in pi times pi^(n-1). Relative error is
* n*error(pi)/pi, requested by mc. Need one more digit in pi if
* n=10, two digits if n=100 etc, and add one extra digit.
*/
MathContext mcpi = new MathContext(mc.getPrecision() + (int) (Math.log10(10.0 * n)));
final BigDecimal piton = pi(mcpi).pow(n, mc);
return multiplyRound(piton, b);
} else if (n == 3) {
/*
* Broadhurst BBP arXiv:math/9803067
* Error propagation: S31 is roughly 0.087, S33 roughly 0.131
*/
int[] a31 = { 1, -7, -1, 10, -1, -7, 1, 0 };
int[] a33 = { 1, 1, -1, -2, -1, 1, 1, 0 };
BigDecimal S31 = broadhurstBBP(3, 1, a31, mc);
BigDecimal S33 = broadhurstBBP(3, 3, a33, mc);
S31 = S31.multiply(new BigDecimal(48));
S33 = S33.multiply(new BigDecimal(32));
return S31.add(S33).divide(new BigDecimal(7), mc);
} else if (n == 5) {
/*
* Broadhurst BBP arXiv:math/9803067
* Error propagation: S51 is roughly -11.15, S53 roughly 22.165, S55
* is roughly 0.031 9*2048*S51/6265 = -3.28. 7*2038*S53/61651= 5.07.
* 738*2048*S55/61651= 0.747. The result is of the order 1.03, so we
* add 2 digits to S51 and S52 and one digit to S55.
*/
int[] a51 = { 31, -1614, -31, -6212, -31, -1614, 31, 74552 };
int[] a53 = { 173, 284, -173, -457, -173, 284, 173, -111 };
int[] a55 = { 1, 0, -1, -1, -1, 0, 1, 1 };
BigDecimal S51 = broadhurstBBP(5, 1, a51, new MathContext(2 + mc.getPrecision()));
BigDecimal S53 = broadhurstBBP(5, 3, a53, new MathContext(2 + mc.getPrecision()));
BigDecimal S55 = broadhurstBBP(5, 5, a55, new MathContext(1 + mc.getPrecision()));
S51 = S51.multiply(new BigDecimal(18432));
S53 = S53.multiply(new BigDecimal(14336));
S55 = S55.multiply(new BigDecimal(1511424));
return S51.add(S53).subtract(S55).divide(new BigDecimal(62651), mc);
} else {
/*
* Cohen et al Exp Math 1 (1) (1992) 25
*/
Rational betsum = new Rational();
Bernoulli bern = new Bernoulli();
Factorial fact = new Factorial();
for (int npr = 0; npr <= (n + 1) / 2; npr++) {
Rational b = bern.at(2 * npr).multiply(bern.at(n + 1 - 2 * npr));
b = b.divide(fact.at(2 * npr)).divide(fact.at(n + 1 - 2 * npr));
b = b.multiply(1 - 2 * npr);
if (npr % 2 == 0)
betsum = betsum.add(b);
else
betsum = betsum.subtract(b);
}
betsum = betsum.divide(n - 1);
/*
* The first term, including the facor (2pi)^n, is essentially most
* of the result, near one. The second term below is roughly in the
* range 0.003 to 0.009. So the precision here is matching the
* precisionn requested by mc, and the precision requested for 2*pi
* is in absolute terms adjusted.
*/
MathContext mcloc = new MathContext(
2 + mc.getPrecision() + (int) (Math.log10((double) (n))));
BigDecimal ftrm = pi(mcloc).multiply(new BigDecimal(2));
ftrm = ftrm.pow(n);
ftrm = multiplyRound(ftrm, betsum.BigDecimalValue(mcloc));
BigDecimal exps = new BigDecimal(0);
/*
* the basic accuracy of the accumulated terms before multiplication
* with 2
*/
double eps = Math.pow(10., -mc.getPrecision());
if (n % 4 == 3) {
/*
* since the argument n is at least 7 here, the drop of the
* terms is at rather constant pace at least 10^-3, for example
* 0.0018, 0.2e-7, 0.29e-11, 0.74e-15 etc for npr=1,2,3.... We
* want 2 times these terms fall below eps/10.
*/
int kmax = mc.getPrecision() / 3;
eps /= kmax;
/*
* need an error of eps for 2/(exp(2pi)-1) = 0.0037 The absolute
* error is 4*exp(2pi)*err(pi)/(exp(2pi)-1)^2=0.0075*err(pi)
*/
BigDecimal exp2p = pi(new MathContext(3 + err2prec(3.14, eps / 0.0075)));
exp2p = exp(exp2p.multiply(new BigDecimal(2)));
BigDecimal c = exp2p.subtract(BigDecimal.ONE);
exps = divideRound(1, c);
for (int npr = 2; npr <= kmax; npr++) {
/*
* the error estimate above for npr=1 is the worst case of
* the absolute error created by an error in 2pi. So we can
* safely re-use the exp2p value computed above without
* reassessment of its error.
*/
c = powRound(exp2p, npr).subtract(BigDecimal.ONE);
c = multiplyRound(c, (new BigInteger("" + npr)).pow(n));
c = divideRound(1, c);
exps = exps.add(c);
}
} else {
/*
* since the argument n is at least 9 here, the drop of the
* terms is at rather constant pace at least 10^-3, for example
* 0.0096, 0.5e-7, 0.3e-11, 0.6e-15 etc. We want these terms
* fall below eps/10.
*/
int kmax = (1 + mc.getPrecision()) / 3;
eps /= kmax;
/*
* need an error of eps for
* 2/(exp(2pi)-1)*(1+4*Pi/8/(1-exp(-2pi)) = 0.0096 at k=7 or =
* 0.00766 at k=13 for example. The absolute error is
* 0.017*err(pi) at k=9, 0.013*err(pi) at k=13, 0.012 at k=17
*/
BigDecimal twop = pi(new MathContext(3 + err2prec(3.14, eps / 0.017)));
twop = twop.multiply(new BigDecimal(2));
BigDecimal exp2p = exp(twop);
BigDecimal c = exp2p.subtract(BigDecimal.ONE);
exps = divideRound(1, c);
c = BigDecimal.ONE.subtract(divideRound(1, exp2p));
c = divideRound(twop, c).multiply(new BigDecimal(2));
c = divideRound(c, n - 1).add(BigDecimal.ONE);
exps = multiplyRound(exps, c);
for (int npr = 2; npr <= kmax; npr++) {
c = powRound(exp2p, npr).subtract(BigDecimal.ONE);
c = multiplyRound(c, (new BigInteger("" + npr)).pow(n));
BigDecimal d = divideRound(1, exp2p.pow(npr));
d = BigDecimal.ONE.subtract(d);
d = divideRound(twop, d).multiply(new BigDecimal(2 * npr));
d = divideRound(d, n - 1).add(BigDecimal.ONE);
d = divideRound(d, c);
exps = exps.add(d);
}
}
exps = exps.multiply(new BigDecimal(2));
return ftrm.subtract(exps, mc);
}
} /* zeta */
static public double zeta1(final int n) {
/*
* precomputed static table in double precision
*/
final double[] zmin1 = { 0., 0., 6.449340668482264364724151666e-01,
2.020569031595942853997381615e-01, 8.232323371113819151600369654e-02,
3.692775514336992633136548646e-02, 1.734306198444913971451792979e-02,
8.349277381922826839797549850e-03, 4.077356197944339378685238509e-03,
2.008392826082214417852769232e-03, 9.945751278180853371459589003e-04,
4.941886041194645587022825265e-04, 2.460865533080482986379980477e-04,
1.227133475784891467518365264e-04, 6.124813505870482925854510514e-05,
3.058823630702049355172851064e-05, 1.528225940865187173257148764e-05,
7.637197637899762273600293563e-06, 3.817293264999839856461644622e-06,
1.908212716553938925656957795e-06, 9.539620338727961131520386834e-07,
4.769329867878064631167196044e-07, 2.384505027277329900036481868e-07,
1.192199259653110730677887189e-07, 5.960818905125947961244020794e-08,
2.980350351465228018606370507e-08, 1.490155482836504123465850663e-08,
7.450711789835429491981004171e-09, 3.725334024788457054819204018e-09,
1.862659723513049006403909945e-09, 9.313274324196681828717647350e-10,
4.656629065033784072989233251e-10, 2.328311833676505492001455976e-10,
1.164155017270051977592973835e-10, 5.820772087902700889243685989e-11,
2.910385044497099686929425228e-11, 1.455192189104198423592963225e-11,
7.275959835057481014520869012e-12, 3.637979547378651190237236356e-12,
1.818989650307065947584832101e-12, 9.094947840263889282533118387e-13,
4.547473783042154026799112029e-13, 2.273736845824652515226821578e-13,
1.136868407680227849349104838e-13, 5.684341987627585609277182968e-14,
2.842170976889301855455073705e-14, 1.421085482803160676983430714e-14,
7.105427395210852712877354480e-15, 3.552713691337113673298469534e-15,
1.776356843579120327473349014e-15, 8.881784210930815903096091386e-16,
4.440892103143813364197770940e-16, 2.220446050798041983999320094e-16,
1.110223025141066133720544570e-16, 5.551115124845481243723736590e-17,
2.775557562136124172581632454e-17, 1.387778780972523276283909491e-17,
6.938893904544153697446085326e-18, 3.469446952165922624744271496e-18,
1.734723476047576572048972970e-18, 8.673617380119933728342055067e-19,
4.336808690020650487497023566e-19, 2.168404344997219785013910168e-19,
1.084202172494241406301271117e-19, 5.421010862456645410918700404e-20,
2.710505431223468831954621312e-20, 1.355252715610116458148523400e-20,
6.776263578045189097995298742e-21, 3.388131789020796818085703100e-21,
1.694065894509799165406492747e-21, 8.470329472546998348246992609e-22,
4.235164736272833347862270483e-22, 2.117582368136194731844209440e-22,
1.058791184068023385226500154e-22, 5.293955920339870323813912303e-23,
2.646977960169852961134116684e-23, 1.323488980084899080309451025e-23,
6.617444900424404067355245332e-24, 3.308722450212171588946956384e-24,
1.654361225106075646229923677e-24, 8.271806125530344403671105617e-25,
4.135903062765160926009382456e-25, 2.067951531382576704395967919e-25,
1.033975765691287099328409559e-25, 5.169878828456431320410133217e-26,
2.584939414228214268127761771e-26, 1.292469707114106670038112612e-26,
6.462348535570531803438002161e-27, 3.231174267785265386134814118e-27,
1.615587133892632521206011406e-27, 8.077935669463162033158738186e-28,
4.038967834731580825622262813e-28, 2.019483917365790349158762647e-28,
1.009741958682895153361925070e-28, 5.048709793414475696084771173e-29,
2.524354896707237824467434194e-29, 1.262177448353618904375399966e-29,
6.310887241768094495682609390e-30, 3.155443620884047239109841220e-30,
1.577721810442023616644432780e-30, 7.888609052210118073520537800e-31 };
if (n <= 0)
throw new ProviderException("Not implemented: zeta at negative argument " + n);
if (n == 1)
throw new ArithmeticException("Pole at zeta(1) ");
if (n < zmin1.length)
/* look it up if available */
return zmin1[n];
else {
/*
* Result is roughly 2^(-n), desired accuracy 18 digits. If zeta(n)
* is computed, the equivalent accuracy in relative units is higher,
* because zeta is around 1.
*/
double eps = 1.e-18 * Math.pow(2., (double) (-n));
MathContext mc = new MathContext(err2prec(eps));
return zeta(n, mc).subtract(BigDecimal.ONE).doubleValue();
}
} /* zeta */
static public double cot(final double x) {
return 1. / Math.tan(x);
}
static public double psi(final double x) {
/*
* the single positive zero of psi(x)
*/
final double psi0 = 1.46163214496836234126265954232572132846819;
if (x > 2.0) {
/*
* Reduce to a value near x=1 with the standard recurrence formula.
* Abramowitz-Stegun 6.3.5
*/
int m = (int) (x - 0.5);
double xmin1 = x - m;
double resul = 0.;
for (int i = 1; i <= m; i++)
resul += 1. / (x - i);
return resul + psi(xmin1);
} else if (Math.abs(x - psi0) < 0.55) {
/*
* Taylor approximation around the local zero
*/
final double[] psiT0 = { 9.67672245447621170427e-01, -4.42763168983592106093e-01,
2.58499760955651010624e-01, -1.63942705442406527504e-01,
1.07824050691262365757e-01, -7.21995612564547109261e-02,
4.88042881641431072251e-02, -3.31611264748473592923e-02,
2.25976482322181046596e-02, -1.54247659049489591388e-02,
1.05387916166121753881e-02, -7.20453438635686824097e-03,
4.92678139572985344635e-03, -3.36980165543932808279e-03,
2.30512632673492783694e-03, -1.57693677143019725927e-03,
1.07882520191629658069e-03, -7.38070938996005129566e-04,
5.04953265834602035177e-04, -3.45468025106307699556e-04,
2.36356015640270527924e-04, -1.61706220919748034494e-04,
1.10633727687474109041e-04, -7.56917958219506591924e-05,
5.17857579522208086899e-05, -3.54300709476596063157e-05,
2.42400661186013176527e-05, -1.65842422718541333752e-05,
1.13463845846638498067e-05, -7.76281766846209442527e-06,
5.31106092088986338732e-06, -3.63365078980104566837e-06,
2.48602273312953794890e-06, -1.70085388543326065825e-06,
1.16366753635488427029e-06, -7.96142543124197040035e-07,
5.44694193066944527850e-07, -3.72661612834382295890e-07,
2.54962655202155425666e-07, -1.74436951177277452181e-07,
1.19343948298302427790e-07, -8.16511518948840884084e-08,
5.58629968353217144428e-08, -3.82196006191749421243e-08,
2.61485769519618662795e-08, -1.78899848649114926515e-08,
1.22397314032336619391e-08, -8.37401629767179054290e-09,
5.72922285984999377160e-09 };
final double xdiff = x - psi0;
double resul = 0.;
for (int i = psiT0.length - 1; i >= 0; i--)
resul = resul * xdiff + psiT0[i];
return resul * xdiff;
} else if (x < 0.) {
/* Reflection formula */
double xmin = 1. - x;
return psi(xmin) + Math.PI / Math.tan(Math.PI * xmin);
} else {
double xmin1 = x - 1;
double resul = 0.;
for (int k = 26; k >= 1; k--) {
resul -= zeta1(2 * k + 1);
resul *= xmin1 * xmin1;
}
/* 0.422... = 1 -gamma */
return resul + 0.422784335098467139393487909917597568 + 0.5 / xmin1
- 1. / (1 - xmin1 * xmin1) - Math.PI / (2. * Math.tan(Math.PI * xmin1));
}
} /* psi */
static protected BigDecimal broadhurstBBP(final int n, final int p, final int a[],
MathContext mc) {
/*
* Explore the actual magnitude of the result first with a quick
* estimate.
*/
double x = 0.0;
for (int k = 1; k < 10; k++)
x += a[(k - 1) % 8] / Math.pow(2., p * (k + 1) / 2) / Math.pow((double) k, n);
/*
* Convert the relative precision and estimate of the result into an
* absolute precision.
*/
double eps = prec2err(x, mc.getPrecision());
/*
* Divide this through the number of terms in the sum to account for
* error accumulation The divisor 2^(p(k+1)/2) means that on the average
* each 8th term in k has shrunk by relative to the 8th predecessor by
* 1/2^(4p). 1/2^(4pc) = 10^(-precision) with c the 8term cycles yields
* c=log_2( 10^precision)/4p = 3.3*precision/4p with k=8c
*/
int kmax = (int) (6.6 * mc.getPrecision() / p);
/* Now eps is the absolute error in each term */
eps /= kmax;
BigDecimal res = BigDecimal.ZERO;
for (int c = 0;; c++) {
Rational r = new Rational();
for (int k = 0; k < 8; k++) {
Rational tmp = new Rational(new BigInteger("" + a[k]),
(new BigInteger("" + (1 + 8 * c + k))).pow(n));
/*
* floor( (pk+p)/2)
*/
int pk1h = p * (2 + 8 * c + k) / 2;
tmp = tmp.divide(BigInteger.ONE.shiftLeft(pk1h));
r = r.add(tmp);
}
if (Math.abs(r.doubleValue()) < eps)
break;
MathContext mcloc = new MathContext(1 + err2prec(r.doubleValue(), eps));
res = res.add(r.BigDecimalValue(mcloc));
}
return res.round(mc);
} /* broadhurstBBP */
static public BigDecimal add(final BigDecimal x, final BigInteger y) {
return x.add(new BigDecimal(y));
} /* add */
static public BigDecimal addRound(final BigDecimal x, final BigDecimal y) {
BigDecimal resul = x.add(y);
/*
* The estimation of the absolute error in the result is
* |err(y)|+|err(x)|
*/
double errR = Math.abs(y.ulp().doubleValue() / 2.) + Math.abs(x.ulp().doubleValue() / 2.);
MathContext mc = new MathContext(err2prec(resul.doubleValue(), errR));
return resul.round(mc);
} /* addRound */
static public BigComplex addRound(final BigComplex x, final BigDecimal y) {
final BigDecimal R = addRound(x.re, y);
return new BigComplex(R, x.im);
} /* addRound */
static public BigComplex addRound(final BigComplex x, final BigComplex y) {
final BigDecimal R = addRound(x.re, y.re);
final BigDecimal I = addRound(x.im, y.im);
return new BigComplex(R, I);
} /* addRound */
static public BigDecimal subtractRound(final BigDecimal x, final BigDecimal y) {
BigDecimal resul = x.subtract(y);
/*
* The estimation of the absolute error in the result is
* |err(y)|+|err(x)|
*/
double errR = Math.abs(y.ulp().doubleValue() / 2.) + Math.abs(x.ulp().doubleValue() / 2.);
MathContext mc = new MathContext(err2prec(resul.doubleValue(), errR));
return resul.round(mc);
} /* subtractRound */
static public BigComplex subtractRound(final BigComplex x, final BigComplex y) {
final BigDecimal R = subtractRound(x.re, y.re);
final BigDecimal I = subtractRound(x.im, y.im);
return new BigComplex(R, I);
} /* subtractRound */
static public BigDecimal multiplyRound(final BigDecimal x, final BigDecimal y) {
BigDecimal resul = x.multiply(y);
/*
* The estimation of the relative error in the result is the sum of the
* relative errors |err(y)/y|+|err(x)/x|
*/
MathContext mc = new MathContext(Math.min(x.precision(), y.precision()));
return resul.round(mc);
} /* multiplyRound */
static public BigComplex multiplyRound(final BigComplex x, final BigDecimal y) {
BigDecimal R = multiplyRound(x.re, y);
BigDecimal I = multiplyRound(x.im, y);
return new BigComplex(R, I);
} /* multiplyRound */
static public BigComplex multiplyRound(final BigComplex x, final BigComplex y) {
BigDecimal R = subtractRound(multiplyRound(x.re, y.re), multiplyRound(x.im, y.im));
BigDecimal I = addRound(multiplyRound(x.re, y.im), multiplyRound(x.im, y.re));
return new BigComplex(R, I);
} /* multiplyRound */
static public BigDecimal multiplyRound(final BigDecimal x, final Rational f) {
if (f.compareTo(BigInteger.ZERO) == 0)
return BigDecimal.ZERO;
else {
/*
* Convert the rational value with two digits of extra precision
*/
MathContext mc = new MathContext(2 + x.precision());
BigDecimal fbd = f.BigDecimalValue(mc);
/*
* and the precision of the product is then dominated by the
* precision in x
*/
return multiplyRound(x, fbd);
}
}
static public BigDecimal multiplyRound(final BigDecimal x, final int n) {
BigDecimal resul = x.multiply(new BigDecimal(n));
/*
* The estimation of the absolute error in the result is |n*err(x)|
*/
MathContext mc = new MathContext(n != 0 ? x.precision() : 0);
return resul.round(mc);
}
static public BigDecimal multiplyRound(final BigDecimal x, final BigInteger n) {
BigDecimal resul = x.multiply(new BigDecimal(n));
/*
* The estimation of the absolute error in the result is |n*err(x)|
*/
MathContext mc = new MathContext(n.compareTo(BigInteger.ZERO) != 0 ? x.precision() : 0);
return resul.round(mc);
}
static public BigDecimal divideRound(final BigDecimal x, final BigDecimal y) {
/*
* The estimation of the relative error in the result is
* |err(y)/y|+|err(x)/x|
*/
MathContext mc = new MathContext(Math.min(x.precision(), y.precision()));
BigDecimal resul = x.divide(y, mc);
/*
* If x and y are precise integer values that may have common factors,
* the method above will truncate trailing zeros, which may result in a
* smaller apparent accuracy than starte... add missing trailing zeros
* now.
*/
return scalePrec(resul, mc);
}
static public BigComplex invertRound(final BigComplex z) {
if (z.im.compareTo(BigDecimal.ZERO) == 0) {
/*
* In this case with vanishing Im(x), the result is simply 1/Re z.
*/
final MathContext mc = new MathContext(z.re.precision());
return new BigComplex(BigDecimal.ONE.divide(z.re, mc));
} else if (z.re.compareTo(BigDecimal.ZERO) == 0) {
/*
* In this case with vanishing Re(z), the result is simply -i/Im z
*/
final MathContext mc = new MathContext(z.im.precision());
return new BigComplex(BigDecimal.ZERO, BigDecimal.ONE.divide(z.im, mc).negate());
} else {
/*
* 1/(x.re+I*x.im) = 1/(x.re+x.im^2/x.re) - I /(x.im +x.re^2/x.im)
*/
BigDecimal R = addRound(z.re, divideRound(multiplyRound(z.im, z.im), z.re));
BigDecimal I = addRound(z.im, divideRound(multiplyRound(z.re, z.re), z.im));
MathContext mc = new MathContext(1 + R.precision());
R = BigDecimal.ONE.divide(R, mc);
mc = new MathContext(1 + I.precision());
I = BigDecimal.ONE.divide(I, mc);
return new BigComplex(R, I.negate());
}
}
static public BigComplex divideRound(final BigComplex x, final BigComplex y) {
return multiplyRound(x, invertRound(y));
}
static public BigDecimal divideRound(final BigDecimal x, final int n) {
/*
* The estimation of the relative error in the result is |err(x)/x|
*/
MathContext mc = new MathContext(x.precision());
return x.divide(new BigDecimal(n), mc);
}
static public BigDecimal divideRound(final BigDecimal x, final BigInteger n) {
/*
* The estimation of the relative error in the result is |err(x)/x|
*/
MathContext mc = new MathContext(x.precision());
return x.divide(new BigDecimal(n), mc);
} /* divideRound */
static public BigDecimal divideRound(final BigInteger n, final BigDecimal x) {
/*
* The estimation of the relative error in the result is |err(x)/x|
*/
MathContext mc = new MathContext(x.precision());
return new BigDecimal(n).divide(x, mc);
} /* divideRound */
static public BigComplex divideRound(final BigInteger n, final BigComplex x) {
/*
* catch case of real-valued denominator first
*/
if (x.im.compareTo(BigDecimal.ZERO) == 0)
return new BigComplex(divideRound(n, x.re), BigDecimal.ZERO);
else if (x.re.compareTo(BigDecimal.ZERO) == 0)
return new BigComplex(BigDecimal.ZERO, divideRound(n, x.im).negate());
BigComplex z = invertRound(x);
/*
* n/(x+iy) = nx/(x^2+y^2) -nyi/(x^2+y^2)
*/
BigDecimal repart = multiplyRound(z.re, n);
BigDecimal impart = multiplyRound(z.im, n);
return new BigComplex(repart, impart);
} /* divideRound */
static public BigDecimal divideRound(final int n, final BigDecimal x) {
/*
* The estimation of the relative error in the result is |err(x)/x|
*/
MathContext mc = new MathContext(x.precision());
return new BigDecimal(n).divide(x, mc);
}
static public BigDecimal scalePrec(final BigDecimal x, int d) {
return x.setScale(d + x.scale());
}
static public BigComplex scalePrec(final BigComplex x, int d) {
return new BigComplex(scalePrec(x.re, d), scalePrec(x.im, d));
}
static public BigDecimal scalePrec(final BigDecimal x, final MathContext mc) {
final int diffPr = mc.getPrecision() - x.precision();
if (diffPr > 0)
return scalePrec(x, diffPr);
else
return x;
} /* BigDecimalMath.scalePrec */
static public int err2prec(BigDecimal x, BigDecimal xerr) {
return err2prec(xerr.divide(x, MathContext.DECIMAL64).doubleValue());
}
static public int err2prec(double x, double xerr) {
/*
* Example: an error of xerr=+-0.5 at x=100 represents 100+-0.5 with a
* precision = 3 (digits).
*/
return 1 + (int) (Math.log10(Math.abs(0.5 * x / xerr)));
}
static public int err2prec(double xerr) {
/*
* Example: an error of xerr=+-0.5 a precision of 1 (digit), an error of
* +-0.05 a precision of 2 (digits)
*/
return 1 + (int) (Math.log10(Math.abs(0.5 / xerr)));
}
static public double prec2err(final double x, final int prec) {
return 5. * Math.abs(x) * Math.pow(10., -prec);
}
} /* BigDecimalMath */
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