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/*
*
* * Copyright 2015 Skymind,Inc.
* *
* * Licensed 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.nd4j.linalg.util;
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
// package org.nevec.rjm ;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.MathContext;
import java.math.RoundingMode;
/**
* Fractions (rational numbers).
* They are divisions of two BigInteger variables, reduced to greatest
* common divisors of 1.
*/
class Rational implements Cloneable {
/* The maximum and minimum value of a standard Java integer, 2^31.
*/
static BigInteger MAX_INT = new BigInteger("2147483647");
static BigInteger MIN_INT = new BigInteger("-2147483648");
static Rational ONE = new Rational(1, 1);
static Rational ZERO = new Rational();
/**
* numerator
*/
BigInteger a;
/**
* denominator
*/
BigInteger b;
/**
* Default ctor, which represents the zero.
*/
public Rational() {
a = BigInteger.ZERO;
b = BigInteger.ONE;
}
/**
* ctor from a numerator and denominator.
*
* @param a the numerator.
* @param b the denominator.
*/
public Rational(BigInteger a, BigInteger b) {
this.a = a;
this.b = b;
normalize();
}
/**
* ctor from a numerator.
*
* @param a the BigInteger.
*/
public Rational(BigInteger a) {
this.a = a;
b = new BigInteger("1");
}
/**
* ctor from a numerator and denominator.
*
* @param a the numerator.
* @param b the denominator.
*/
public Rational(int a, int b) {
this(new BigInteger("" + a), new BigInteger("" + b));
}
/**
* ctor from a string representation.
*
* @param str the string.
* This either has a slash in it, separating two integers, or, if there is no slash,
* is representing the numerator with implicit denominator equal to 1.
* @warning this does not yet test for a denominator equal to zero
*/
public Rational(String str) throws NumberFormatException {
this(str, 10);
}
/**
* ctor from a string representation in a specified base.
*
* @param str the string.
* This either has a slash in it, separating two integers, or, if there is no slash,
* is just representing the numerator.
* @param radix the number base for numerator and denominator
* @warning this does not yet test for a denominator equal to zero
* 5
*/
public Rational(String str, int radix) throws NumberFormatException {
int hasslah = str.indexOf("/");
if (hasslah == -1) {
a = new BigInteger(str, radix);
b = new BigInteger("1", radix);
/* no normalization necessary here */
} else {
/* create numerator and denominator separately
*/
a = new BigInteger(str.substring(0, hasslah), radix);
b = new BigInteger(str.substring(hasslah + 1), radix);
normalize();
}
}
/**
* binomial (n choose m).
*
* @param n the numerator. Equals the size of the set to choose from.
* @param m the denominator. Equals the number of elements to select.
* @return the binomial coefficient.
*/
public static Rational binomial(Rational n, BigInteger m) {
if (m.compareTo(BigInteger.ZERO) == 0) {
return Rational.ONE;
}
Rational bin = n;
for (BigInteger i = new BigInteger("2"); i.compareTo(m) != 1; i = i.add(BigInteger.ONE)) {
bin = bin.multiply(n.subtract(i.subtract(BigInteger.ONE))).divide(i);
}
return bin;
} /* Rational.binomial */
/**
* binomial (n choose m).
*
* @param n the numerator. Equals the size of the set to choose from.
* @param m the denominator. Equals the number of elements to select.
* @return the binomial coefficient.
*/
public static Rational binomial(Rational n, int m) {
if (m == 0) {
return Rational.ONE;
}
Rational bin = n;
for (int i = 2; i <= m; i++) {
bin = bin.multiply(n.subtract(i - 1)).divide(i);
}
return bin;
} /* Rational.binomial */
/**
* Create a copy.
*/
@Override
public Rational clone() {
/* protected access means this does not work
* return new Rational(a.clone(), b.clone()) ;
*/
BigInteger aclon = new BigInteger("" + a);
BigInteger bclon = new BigInteger("" + b);
return new Rational(aclon, bclon);
} /* Rational.clone */
/**
* Multiply by another fraction.
*
* @param val a second rational number.
* @return the product of this with the val.
*/
public Rational multiply(final Rational val) {
BigInteger num = a.multiply(val.a);
BigInteger deno = b.multiply(val.b);
/* Normalization to an coprime format will be done inside
* the ctor() and is not duplicated here.
*/
return (new Rational(num, deno));
} /* Rational.multiply */
/**
* Multiply by a BigInteger.
*
* @param val a second number.
* @return the product of this with the value.
*/
public Rational multiply(final BigInteger val) {
Rational val2 = new Rational(val, BigInteger.ONE);
return (multiply(val2));
} /* Rational.multiply */
/**
* Multiply by an integer.
*
* @param val a second number.
* @return the product of this with the value.
*/
public Rational multiply(final int val) {
BigInteger tmp = new BigInteger("" + val);
return multiply(tmp);
} /* Rational.multiply */
/**
* Power to an integer.
*
* @param exponent the exponent.
* @return this value raised to the power given by the exponent.
* If the exponent is 0, the value 1 is returned.
*/
public Rational pow(int exponent) {
if (exponent == 0) {
return new Rational(1, 1);
}
BigInteger num = a.pow(Math.abs(exponent));
BigInteger deno = b.pow(Math.abs(exponent));
if (exponent > 0) {
return (new Rational(num, deno));
} else {
return (new Rational(deno, num));
}
} /* Rational.pow */
/**
* Power to an integer.
*
* @param exponent the exponent.
* @return this value raised to the power given by the exponent.
* If the exponent is 0, the value 1 is returned.
*/
public Rational pow(BigInteger exponent) throws NumberFormatException {
/* test for overflow */
if (exponent.compareTo(MAX_INT) == 1) {
throw new NumberFormatException("Exponent " + exponent.toString() + " too large.");
}
if (exponent.compareTo(MIN_INT) == -1) {
throw new NumberFormatException("Exponent " + exponent.toString() + " too small.");
}
/* promote to the simpler interface above */
return pow(exponent.intValue());
} /* Rational.pow */
/**
* Divide by another fraction.
*
* @param val A second rational number.
* @return The value of this/val
*/
public Rational divide(final Rational val) {
BigInteger num = a.multiply(val.b);
BigInteger deno = b.multiply(val.a);
/* Reduction to a coprime format is done inside the ctor,
* and not repeated here.
*/
return (new Rational(num, deno));
} /* Rational.divide */
/**
* Divide by an integer.
*
* @param val a second number.
* @return the value of this/val
*/
public Rational divide(BigInteger val) {
Rational val2 = new Rational(val, BigInteger.ONE);
return (divide(val2));
} /* Rational.divide */
/**
* Divide by an integer.
*
* @param val A second number.
* @return The value of this/val
*/
public Rational divide(int val) {
Rational val2 = new Rational(val, 1);
return (divide(val2));
} /* Rational.divide */
/**
* Add another fraction.
*
* @param val The number to be added
* @return this+val.
*/
public Rational add(Rational val) {
BigInteger num = a.multiply(val.b).add(b.multiply(val.a));
BigInteger deno = b.multiply(val.b);
return (new Rational(num, deno));
} /* Rational.add */
/**
* Add another integer.
*
* @param val The number to be added
* @return this+val.
*/
public Rational add(BigInteger val) {
Rational val2 = new Rational(val, BigInteger.ONE);
return (add(val2));
} /* Rational.add */
/**
* Compute the negative.
*
* @return -this.
*/
public Rational negate() {
return (new Rational(a.negate(), b));
} /* Rational.negate */
/**
* Subtract another fraction.
* 7
*
* @param val the number to be subtracted from this
* @return this - val.
*/
public Rational subtract(Rational val) {
Rational val2 = val.negate();
return (add(val2));
} /* Rational.subtract */
/**
* Subtract an integer.
*
* @param val the number to be subtracted from this
* @return this - val.
*/
public Rational subtract(BigInteger val) {
Rational val2 = new Rational(val, BigInteger.ONE);
return (subtract(val2));
} /* Rational.subtract */
/**
* Subtract an integer.
*
* @param val the number to be subtracted from this
* @return this - val.
*/
public Rational subtract(int val) {
Rational val2 = new Rational(val, 1);
return (subtract(val2));
} /* Rational.subtract */
/**
* Get the numerator.
*
* @return The numerator of the reduced fraction.
*/
public BigInteger numer() {
return a;
}
/**
* Get the denominator.
*
* @return The denominator of the reduced fraction.
*/
public BigInteger denom() {
return b;
}
/**
* Absolute value.
*
* @return The absolute (non-negative) value of this.
*/
public Rational abs() {
return (new Rational(a.abs(), b.abs()));
}
/**
* floor(): the nearest integer not greater than this.
*
* @return The integer rounded towards negative infinity.
*/
public BigInteger floor() {
/* is already integer: return the numerator
*/
if (b.compareTo(BigInteger.ONE) == 0) {
return a;
} else if (a.compareTo(BigInteger.ZERO) > 0) {
return a.divide(b);
} else {
return a.divide(b).subtract(BigInteger.ONE);
}
} /* Rational.floor */
/**
* Remove the fractional part.
*
* @return The integer rounded towards zero.
*/
public BigInteger trunc() {
/* is already integer: return the numerator
*/
if (b.compareTo(BigInteger.ONE) == 0) {
return a;
} else {
return a.divide(b);
}
} /* Rational.trunc */
/**
* Compares the value of this with another constant.
*
* @param val the other constant to compare with
* @return -1, 0 or 1 if this number is numerically less than, equal to,
* or greater than val.
*/
public int compareTo(final Rational val) {
/* Since we have always kept the denominators positive,
* simple cross-multiplying works without changing the sign.
*/
final BigInteger left = a.multiply(val.b);
final BigInteger right = val.a.multiply(b);
return left.compareTo(right);
} /* Rational.compareTo */
/**
* Compares the value of this with another constant.
*
* @param val the other constant to compare with
* @return -1, 0 or 1 if this number is numerically less than, equal to,
* or greater than val.
*/
public int compareTo(final BigInteger val) {
final Rational val2 = new Rational(val, BigInteger.ONE);
return (compareTo(val2));
} /* Rational.compareTo */
/**
* Return a string in the format number/denom.
* If the denominator equals 1, print just the numerator without a slash.
*
* @return the human-readable version in base 10
*/
@Override
public String toString() {
if (b.compareTo(BigInteger.ONE) != 0) {
return (a.toString() + "/" + b.toString());
} else {
return a.toString();
}
} /* Rational.toString */
/**
* Return a double value representation.
*
* @return The value with double precision.
*/
public double doubleValue() {
/* To meet the risk of individual overflows of the exponents of
* a separate invocation a.doubleValue() or b.doubleValue(), we divide first
* in a BigDecimal environment and converst the result.
*/
BigDecimal adivb = (new BigDecimal(a)).divide(new BigDecimal(b), MathContext.DECIMAL128);
return adivb.doubleValue();
} /* Rational.doubleValue */
/**
* Return a float value representation.
*
* @return The value with single precision.
*/
public float floatValue() {
BigDecimal adivb = (new BigDecimal(a)).divide(new BigDecimal(b), MathContext.DECIMAL128);
return adivb.floatValue();
} /* Rational.floatValue */
/**
* Return a representation as BigDecimal.
*
* @param mc the mathematical context which determines precision, rounding mode etc
* @return A representation as a BigDecimal floating point number.
*/
public BigDecimal BigDecimalValue(MathContext mc) {
/* numerator and denominator individually rephrased
*/
BigDecimal n = new BigDecimal(a);
BigDecimal d = new BigDecimal(b);
return n.divide(d, mc);
} /* Rational.BigDecimnalValue */
/**
* Return a string in floating point format.
*
* @param digits The precision (number of digits)
* @return The human-readable version in base 10.
*/
public String toFString(int digits) {
if (b.compareTo(BigInteger.ONE) != 0) {
MathContext mc = new MathContext(digits, RoundingMode.DOWN);
BigDecimal f = (new BigDecimal(a)).divide(new BigDecimal(b), mc);
return (f.toString());
} else {
return a.toString();
}
} /* Rational.toFString */
/**
* Compares the value of this with another constant.
*
* @param val The other constant to compare with
* @return The arithmetic maximum of this and val.
*/
public Rational max(final Rational val) {
if (compareTo(val) > 0) {
return this;
} else {
return val;
}
} /* Rational.max */
/**
* Compares the value of this with another constant.
*
* @param val The other constant to compare with
* @return The arithmetic minimum of this and val.
*/
public Rational min(final Rational val) {
if (compareTo(val) < 0) {
return this;
} else {
return val;
}
} /* Rational.min */
/**
* Compute Pochhammer’s symbol (this)_n.
*
* @param n The number of product terms in the evaluation.
* @return Gamma(this+n)/Gamma(this) = this*(this+1)*...*(this+n-1).
*/
public Rational Pochhammer(final BigInteger n) {
if (n.compareTo(BigInteger.ZERO) < 0) {
return null;
} else if (n.compareTo(BigInteger.ZERO) == 0) {
return Rational.ONE;
} else {
/* initialize results with the current value
*/
Rational res = new Rational(a, b);
BigInteger i = BigInteger.ONE;
for (; i.compareTo(n) < 0; i = i.add(BigInteger.ONE)) {
res = res.multiply(add(i));
}
return res;
}
} /* Rational.pochhammer */
/**
* Compute pochhammer’s symbol (this)_n.
*
* @param n The number of product terms in the evaluation.
* @return Gamma(this+n)/GAMMA(this).
*/
public Rational Pochhammer(int n) {
return Pochhammer(new BigInteger("" + n));
} /* Rational.pochhammer */
/**
* Normalize to coprime numerator and denominator.
* Also copy a negative sign of the denominator to the numerator.
*/
protected void normalize() {
/* compute greatest common divisor of numerator and denominator
*/
final BigInteger g = a.gcd(b);
if (g.compareTo(BigInteger.ONE) > 0) {
a = a.divide(g);
b = b.divide(g);
}
if (b.compareTo(BigInteger.ZERO) == -1) {
a = a.negate();
b = b.negate();
}
} /* Rational.normalize */
} /* Rational */
