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/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.examples.pi.math;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import org.apache.hadoop.examples.pi.Container;
import org.apache.hadoop.examples.pi.Util;
/**
* Bellard's BBP-type Pi formula
* 1/2^6 \sum_{n=0}^\infty (-1)^n/2^{10n}
* (-2^5/(4n+1) -1/(4n+3) +2^8/(10n+1) -2^6/(10n+3) -2^2/(10n+5)
* -2^2/(10n+7) +1/(10n+9))
*
* References:
*
* [1] David H. Bailey, Peter B. Borwein and Simon Plouffe. On the Rapid
* Computation of Various Polylogarithmic Constants.
* Math. Comp., 66:903-913, 1996.
*
* [2] Fabrice Bellard. A new formula to compute the n'th binary digit of pi,
* 1997. Available at http://fabrice.bellard.free.fr/pi .
*/
public final class Bellard {
/** Parameters for the sums */
public enum Parameter {
// \sum_{k=0}^\infty (-1)^{k+1}( 2^{d-10k-1}/(4k+1) + 2^{d-10k-6}/(4k+3) )
P8_1(false, 1, 8, -1),
P8_3(false, 3, 8, -6),
P8_5(P8_1),
P8_7(P8_3),
/*
* 2^d\sum_{k=0}^\infty (-1)^k( 2^{ 2-10k} / (10k + 1)
* -2^{ -10k} / (10k + 3)
* -2^{-4-10k} / (10k + 5)
* -2^{-4-10k} / (10k + 7)
* +2^{-6-10k} / (10k + 9) )
*/
P20_21(true , 1, 20, 2),
P20_3(false, 3, 20, 0),
P20_5(false, 5, 20, -4),
P20_7(false, 7, 20, -4),
P20_9(true , 9, 20, -6),
P20_11(P20_21),
P20_13(P20_3),
P20_15(P20_5),
P20_17(P20_7),
P20_19(P20_9);
final boolean isplus;
final long j;
final int deltaN;
final int deltaE;
final int offsetE;
private Parameter(boolean isplus, long j, int deltaN, int offsetE) {
this.isplus = isplus;
this.j = j;
this.deltaN = deltaN;
this.deltaE = -20;
this.offsetE = offsetE;
}
private Parameter(Parameter p) {
this.isplus = !p.isplus;
this.j = p.j + (p.deltaN >> 1);
this.deltaN = p.deltaN;
this.deltaE = p.deltaE;
this.offsetE = p.offsetE + (p.deltaE >> 1);
}
/** Get the Parameter represented by the String */
public static Parameter get(String s) {
s = s.trim();
if (s.charAt(0) == 'P')
s = s.substring(1);
final String[] parts = s.split("\\D+");
if (parts.length >= 2) {
final String name = "P" + parts[0] + "_" + parts[1];
for(Parameter p : values())
if (p.name().equals(name))
return p;
}
throw new IllegalArgumentException("s=" + s
+ ", parts=" + Arrays.asList(parts));
}
}
/** The sums in the Bellard's formula */
public static class Sum implements Container, Iterable {
private static final long ACCURACY_BIT = 50;
private final Parameter parameter;
private final Summation sigma;
private final Summation[] parts;
private final Tail tail;
/** Constructor */
private > Sum(long b, Parameter p, int nParts, List existing) {
if (b < 0)
throw new IllegalArgumentException("b = " + b + " < 0");
if (nParts < 1)
throw new IllegalArgumentException("nParts = " + nParts + " < 1");
final long i = p.j == 1 && p.offsetE >= 0? 1 : 0;
final long e = b + i*p.deltaE + p.offsetE;
final long n = i*p.deltaN + p.j;
this.parameter = p;
this.sigma = new Summation(n, p.deltaN, e, p.deltaE, 0);
this.parts = partition(sigma, nParts, existing);
this.tail = new Tail(n, e);
}
private static > Summation[] partition(
Summation sigma, int nParts, List existing) {
final List parts = new ArrayList();
if (existing == null || existing.isEmpty())
parts.addAll(Arrays.asList(sigma.partition(nParts)));
else {
final long stepsPerPart = sigma.getSteps()/nParts;
final List remaining = sigma.remainingTerms(existing);
for(Summation s : remaining) {
final int n = (int)((s.getSteps() - 1)/stepsPerPart) + 1;
parts.addAll(Arrays.asList(s.partition(n)));
}
for(Container c : existing)
parts.add(c.getElement());
Collections.sort(parts);
}
return parts.toArray(new Summation[parts.size()]);
}
/** {@inheritDoc} */
@Override
public String toString() {
int n = 0;
for(Summation s : parts)
if (s.getValue() == null)
n++;
return getClass().getSimpleName() + "{" + parameter + ": " + sigma
+ ", remaining=" + n + "}";
}
/** Set the value of sigma */
public void setValue(Summation s) {
if (s.getValue() == null)
throw new IllegalArgumentException("s.getValue()"
+ "\n sigma=" + sigma
+ "\n s =" + s);
if (!s.contains(sigma) || !sigma.contains(s))
throw new IllegalArgumentException("!s.contains(sigma) || !sigma.contains(s)"
+ "\n sigma=" + sigma
+ "\n s =" + s);
sigma.setValue(s.getValue());
}
/** get the value of sigma */
public double getValue() {
if (sigma.getValue() == null) {
double d = 0;
for(int i = 0; i < parts.length; i++)
d = Modular.addMod(d, parts[i].compute());
sigma.setValue(d);
}
final double s = Modular.addMod(sigma.getValue(), tail.compute());
return parameter.isplus? s: -s;
}
/** {@inheritDoc} */
@Override
public Summation getElement() {
if (sigma.getValue() == null) {
int i = 0;
double d = 0;
for(; i < parts.length && parts[i].getValue() != null; i++)
d = Modular.addMod(d, parts[i].getValue());
if (i == parts.length)
sigma.setValue(d);
}
return sigma;
}
/** The sum tail */
private class Tail {
private long n;
private long e;
private Tail(long n, long e) {
this.n = n;
this.e = e;
}
private double compute() {
if (e > 0) {
final long edelta = -sigma.E.delta;
long q = e / edelta;
long r = e % edelta;
if (r == 0) {
e = 0;
n += q * sigma.N.delta;
} else {
e = edelta - r;
n += (q + 1)*sigma.N.delta;
}
} else if (e < 0)
e = -e;
double s = 0;
for(;; e -= sigma.E.delta) {
if (e > ACCURACY_BIT || (1L << (ACCURACY_BIT - e)) < n)
return s;
s += 1.0 / (n << e);
if (s >= 1) s--;
n += sigma.N.delta;
}
}
}
/** {@inheritDoc} */
@Override
public Iterator iterator() {
return new Iterator() {
private int i = 0;
/** {@inheritDoc} */
@Override
public boolean hasNext() {return i < parts.length;}
/** {@inheritDoc} */
@Override
public Summation next() {return parts[i++];}
/** Unsupported */
@Override
public void remove() {throw new UnsupportedOperationException();}
};
}
}
/** Get the sums for the Bellard formula. */
public static > Map getSums(
long b, int partsPerSum, Map> existing) {
final Map sums = new TreeMap();
for(Parameter p : Parameter.values()) {
final Sum s = new Sum(b, p, partsPerSum, existing.get(p));
Util.out.println("put " + s);
sums.put(p, s);
}
return sums;
}
/** Compute bits of Pi from the results. */
public static > double computePi(
final long b, Map results) {
if (results.size() != Parameter.values().length)
throw new IllegalArgumentException("m.size() != Parameter.values().length"
+ ", m.size()=" + results.size()
+ "\n m=" + results);
double pi = 0;
for(Parameter p : Parameter.values()) {
final Summation sigma = results.get(p).getElement();
final Sum s = new Sum(b, p, 1, null);
s.setValue(sigma);
pi = Modular.addMod(pi, s.getValue());
}
return pi;
}
/** Compute bits of Pi in the local machine. */
public static double computePi(final long b) {
double pi = 0;
for(Parameter p : Parameter.values())
pi = Modular.addMod(pi, new Sum(b, p, 1, null).getValue());
return pi;
}
/** Estimate the number of terms. */
public static long bit2terms(long b) {
return 7*(b/10);
}
private static void computePi(Util.Timer t, long b) {
t.tick(Util.pi2string(computePi(b), bit2terms(b)));
}
/** main */
public static void main(String[] args) throws IOException {
final Util.Timer t = new Util.Timer(false);
computePi(t, 0);
computePi(t, 1);
computePi(t, 2);
computePi(t, 3);
computePi(t, 4);
Util.printBitSkipped(1008);
computePi(t, 1008);
computePi(t, 1012);
long b = 10;
for(int i = 0; i < 7; i++) {
Util.printBitSkipped(b);
computePi(t, b - 4);
computePi(t, b);
computePi(t, b + 4);
b *= 10;
}
}
}