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Commons Math example source code file (MathUtils.java)
This example Commons Math source code file (MathUtils.java) is included in the DevDaily.com
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Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.
The Commons Math MathUtils.java source code
/*
* 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.commons.math.util;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Arrays;
import org.apache.commons.math.MathRuntimeException;
/**
* Some useful additions to the built-in functions in {@link Math}.
* @version $Revision: 927249 $ $Date: 2010-03-24 21:06:51 -0400 (Wed, 24 Mar 2010) $
*/
public final class MathUtils {
/** Smallest positive number such that 1 - EPSILON is not numerically equal to 1. */
public static final double EPSILON = 0x1.0p-53;
/** Safe minimum, such that 1 / SAFE_MIN does not overflow.
* <p>In IEEE 754 arithmetic, this is also the smallest normalized
* number 2<sup>-1022.
*/
public static final double SAFE_MIN = 0x1.0p-1022;
/**
* 2 ?.
* @since 2.1
*/
public static final double TWO_PI = 2 * Math.PI;
/** -1.0 cast as a byte. */
private static final byte NB = (byte)-1;
/** -1.0 cast as a short. */
private static final short NS = (short)-1;
/** 1.0 cast as a byte. */
private static final byte PB = (byte)1;
/** 1.0 cast as a short. */
private static final short PS = (short)1;
/** 0.0 cast as a byte. */
private static final byte ZB = (byte)0;
/** 0.0 cast as a short. */
private static final short ZS = (short)0;
/** Gap between NaN and regular numbers. */
private static final int NAN_GAP = 4 * 1024 * 1024;
/** Offset to order signed double numbers lexicographically. */
private static final long SGN_MASK = 0x8000000000000000L;
/** All long-representable factorials */
private static final long[] FACTORIALS = new long[] {
1l, 1l, 2l,
6l, 24l, 120l,
720l, 5040l, 40320l,
362880l, 3628800l, 39916800l,
479001600l, 6227020800l, 87178291200l,
1307674368000l, 20922789888000l, 355687428096000l,
6402373705728000l, 121645100408832000l, 2432902008176640000l };
/**
* Private Constructor
*/
private MathUtils() {
super();
}
/**
* Add two integers, checking for overflow.
*
* @param x an addend
* @param y an addend
* @return the sum <code>x+y
* @throws ArithmeticException if the result can not be represented as an
* int
* @since 1.1
*/
public static int addAndCheck(int x, int y) {
long s = (long)x + (long)y;
if (s < Integer.MIN_VALUE || s > Integer.MAX_VALUE) {
throw new ArithmeticException("overflow: add");
}
return (int)s;
}
/**
* Add two long integers, checking for overflow.
*
* @param a an addend
* @param b an addend
* @return the sum <code>a+b
* @throws ArithmeticException if the result can not be represented as an
* long
* @since 1.2
*/
public static long addAndCheck(long a, long b) {
return addAndCheck(a, b, "overflow: add");
}
/**
* Add two long integers, checking for overflow.
*
* @param a an addend
* @param b an addend
* @param msg the message to use for any thrown exception.
* @return the sum <code>a+b
* @throws ArithmeticException if the result can not be represented as an
* long
* @since 1.2
*/
private static long addAndCheck(long a, long b, String msg) {
long ret;
if (a > b) {
// use symmetry to reduce boundary cases
ret = addAndCheck(b, a, msg);
} else {
// assert a <= b
if (a < 0) {
if (b < 0) {
// check for negative overflow
if (Long.MIN_VALUE - b <= a) {
ret = a + b;
} else {
throw new ArithmeticException(msg);
}
} else {
// opposite sign addition is always safe
ret = a + b;
}
} else {
// assert a >= 0
// assert b >= 0
// check for positive overflow
if (a <= Long.MAX_VALUE - b) {
ret = a + b;
} else {
throw new ArithmeticException(msg);
}
}
}
return ret;
}
/**
* Returns an exact representation of the <a
* href="http://mathworld.wolfram.com/BinomialCoefficient.html"> Binomial
* Coefficient</a>, "n choose k", the number of
* <code>k-element subsets that can be selected from an
* <code>n-element set.
* <p>
* <Strong>Preconditions:
* <ul>
* <li> 0 <= k <= n (otherwise
* <code>IllegalArgumentException is thrown)
* <li> The result is small enough to fit into a long. The
* largest value of <code>n for which all coefficients are
* <code> < Long.MAX_VALUE is 66. If the computed value exceeds
* <code>Long.MAX_VALUE an ArithMeticException is
* thrown.</li>
* </ul>
*
* @param n the size of the set
* @param k the size of the subsets to be counted
* @return <code>n choose k
* @throws IllegalArgumentException if preconditions are not met.
* @throws ArithmeticException if the result is too large to be represented
* by a long integer.
*/
public static long binomialCoefficient(final int n, final int k) {
checkBinomial(n, k);
if ((n == k) || (k == 0)) {
return 1;
}
if ((k == 1) || (k == n - 1)) {
return n;
}
// Use symmetry for large k
if (k > n / 2)
return binomialCoefficient(n, n - k);
// We use the formula
// (n choose k) = n! / (n-k)! / k!
// (n choose k) == ((n-k+1)*...*n) / (1*...*k)
// which could be written
// (n choose k) == (n-1 choose k-1) * n / k
long result = 1;
if (n <= 61) {
// For n <= 61, the naive implementation cannot overflow.
int i = n - k + 1;
for (int j = 1; j <= k; j++) {
result = result * i / j;
i++;
}
} else if (n <= 66) {
// For n > 61 but n <= 66, the result cannot overflow,
// but we must take care not to overflow intermediate values.
int i = n - k + 1;
for (int j = 1; j <= k; j++) {
// We know that (result * i) is divisible by j,
// but (result * i) may overflow, so we split j:
// Filter out the gcd, d, so j/d and i/d are integer.
// result is divisible by (j/d) because (j/d)
// is relative prime to (i/d) and is a divisor of
// result * (i/d).
final long d = gcd(i, j);
result = (result / (j / d)) * (i / d);
i++;
}
} else {
// For n > 66, a result overflow might occur, so we check
// the multiplication, taking care to not overflow
// unnecessary.
int i = n - k + 1;
for (int j = 1; j <= k; j++) {
final long d = gcd(i, j);
result = mulAndCheck(result / (j / d), i / d);
i++;
}
}
return result;
}
/**
* Returns a <code>double representation of the n choose k", the number of
* <code>k-element subsets that can be selected from an
* <code>n-element set.
* <p>
* <Strong>Preconditions:
* <ul>
* <li> 0 <= k <= n (otherwise
* <code>IllegalArgumentException is thrown)
* <li> The result is small enough to fit into a double. The
* largest value of <code>n for which all coefficients are <
* Double.MAX_VALUE is 1029. If the computed value exceeds Double.MAX_VALUE,
* Double.POSITIVE_INFINITY is returned</li>
* </ul>
*
* @param n the size of the set
* @param k the size of the subsets to be counted
* @return <code>n choose k
* @throws IllegalArgumentException if preconditions are not met.
*/
public static double binomialCoefficientDouble(final int n, final int k) {
checkBinomial(n, k);
if ((n == k) || (k == 0)) {
return 1d;
}
if ((k == 1) || (k == n - 1)) {
return n;
}
if (k > n/2) {
return binomialCoefficientDouble(n, n - k);
}
if (n < 67) {
return binomialCoefficient(n,k);
}
double result = 1d;
for (int i = 1; i <= k; i++) {
result *= (double)(n - k + i) / (double)i;
}
return Math.floor(result + 0.5);
}
/**
* Returns the natural <code>log of the n choose k", the number of
* <code>k-element subsets that can be selected from an
* <code>n-element set.
* <p>
* <Strong>Preconditions:
* <ul>
* <li> 0 <= k <= n (otherwise
* <code>IllegalArgumentException is thrown)
* </ul>
*
* @param n the size of the set
* @param k the size of the subsets to be counted
* @return <code>n choose k
* @throws IllegalArgumentException if preconditions are not met.
*/
public static double binomialCoefficientLog(final int n, final int k) {
checkBinomial(n, k);
if ((n == k) || (k == 0)) {
return 0;
}
if ((k == 1) || (k == n - 1)) {
return Math.log(n);
}
/*
* For values small enough to do exact integer computation,
* return the log of the exact value
*/
if (n < 67) {
return Math.log(binomialCoefficient(n,k));
}
/*
* Return the log of binomialCoefficientDouble for values that will not
* overflow binomialCoefficientDouble
*/
if (n < 1030) {
return Math.log(binomialCoefficientDouble(n, k));
}
if (k > n / 2) {
return binomialCoefficientLog(n, n - k);
}
/*
* Sum logs for values that could overflow
*/
double logSum = 0;
// n!/(n-k)!
for (int i = n - k + 1; i <= n; i++) {
logSum += Math.log(i);
}
// divide by k!
for (int i = 2; i <= k; i++) {
logSum -= Math.log(i);
}
return logSum;
}
/**
* Check binomial preconditions.
* @param n the size of the set
* @param k the size of the subsets to be counted
* @exception IllegalArgumentException if preconditions are not met.
*/
private static void checkBinomial(final int n, final int k)
throws IllegalArgumentException {
if (n < k) {
throw MathRuntimeException.createIllegalArgumentException(
"must have n >= k for binomial coefficient (n,k), got n = {0}, k = {1}",
n, k);
}
if (n < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"must have n >= 0 for binomial coefficient (n,k), got n = {0}",
n);
}
}
/**
* Compares two numbers given some amount of allowed error.
*
* @param x the first number
* @param y the second number
* @param eps the amount of error to allow when checking for equality
* @return <ul>0 if {@link #equals(double, double, double) equals(x, y, eps)}
* <li>< 0 if !{@link #equals(double, double, double) equals(x, y, eps)} && x < y
* <li>> 0 if !{@link #equals(double, double, double) equals(x, y, eps)} && x > y
*/
public static int compareTo(double x, double y, double eps) {
if (equals(x, y, eps)) {
return 0;
} else if (x < y) {
return -1;
}
return 1;
}
/**
* Returns the <a href="http://mathworld.wolfram.com/HyperbolicCosine.html">
* hyperbolic cosine</a> of x.
*
* @param x double value for which to find the hyperbolic cosine
* @return hyperbolic cosine of x
*/
public static double cosh(double x) {
return (Math.exp(x) + Math.exp(-x)) / 2.0;
}
/**
* Returns true iff both arguments are NaN or neither is NaN and they are
* equal
*
* @param x first value
* @param y second value
* @return true if the values are equal or both are NaN
*/
public static boolean equals(double x, double y) {
return (Double.isNaN(x) && Double.isNaN(y)) || x == y;
}
/**
* Returns true iff both arguments are equal or within the range of allowed
* error (inclusive).
* <p>
* Two NaNs are considered equals, as are two infinities with same sign.
* </p>
*
* @param x first value
* @param y second value
* @param eps the amount of absolute error to allow
* @return true if the values are equal or within range of each other
*/
public static boolean equals(double x, double y, double eps) {
return equals(x, y) || (Math.abs(y - x) <= eps);
}
/**
* Returns true iff both arguments are equal or within the range of allowed
* error (inclusive).
* Adapted from <a
* href="http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm">
* Bruce Dawson</a>
*
* @param x first value
* @param y second value
* @param maxUlps {@code (maxUlps - 1)} is the number of floating point
* values between {@code x} and {@code y}.
* @return {@code true} if there are less than {@code maxUlps} floating
* point values between {@code x} and {@code y}
*/
public static boolean equals(double x, double y, int maxUlps) {
// Check that "maxUlps" is non-negative and small enough so that the
// default NAN won't compare as equal to anything.
assert maxUlps > 0 && maxUlps < NAN_GAP;
long xInt = Double.doubleToLongBits(x);
long yInt = Double.doubleToLongBits(y);
// Make lexicographically ordered as a two's-complement integer.
if (xInt < 0) {
xInt = SGN_MASK - xInt;
}
if (yInt < 0) {
yInt = SGN_MASK - yInt;
}
return Math.abs(xInt - yInt) <= maxUlps;
}
/**
* Returns true iff both arguments are null or have same dimensions
* and all their elements are {@link #equals(double,double) equals}
*
* @param x first array
* @param y second array
* @return true if the values are both null or have same dimension
* and equal elements
* @since 1.2
*/
public static boolean equals(double[] x, double[] y) {
if ((x == null) || (y == null)) {
return !((x == null) ^ (y == null));
}
if (x.length != y.length) {
return false;
}
for (int i = 0; i < x.length; ++i) {
if (!equals(x[i], y[i])) {
return false;
}
}
return true;
}
/**
* Returns n!. Shorthand for <code>n , the
* product of the numbers <code>1,...,n.
* <p>
* <Strong>Preconditions:
* <ul>
* <li> n >= 0 (otherwise
* <code>IllegalArgumentException is thrown)
* <li> The result is small enough to fit into a long. The
* largest value of <code>n for which n! <
* Long.MAX_VALUE</code> is 20. If the computed value exceeds Long.MAX_VALUE
* an <code>ArithMeticException is thrown.
* </ul>
* </p>
*
* @param n argument
* @return <code>n!
* @throws ArithmeticException if the result is too large to be represented
* by a long integer.
* @throws IllegalArgumentException if n < 0
*/
public static long factorial(final int n) {
if (n < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"must have n >= 0 for n!, got n = {0}",
n);
}
if (n > 20) {
throw new ArithmeticException(
"factorial value is too large to fit in a long");
}
return FACTORIALS[n];
}
/**
* Returns n!. Shorthand for <code>n , the
* product of the numbers <code>1,...,n as a double.
* <p>
* <Strong>Preconditions:
* <ul>
* <li> n >= 0 (otherwise
* <code>IllegalArgumentException is thrown)
* <li> The result is small enough to fit into a double. The
* largest value of <code>n for which n! <
* Double.MAX_VALUE</code> is 170. If the computed value exceeds
* Double.MAX_VALUE, Double.POSITIVE_INFINITY is returned</li>
* </ul>
* </p>
*
* @param n argument
* @return <code>n!
* @throws IllegalArgumentException if n < 0
*/
public static double factorialDouble(final int n) {
if (n < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"must have n >= 0 for n!, got n = {0}",
n);
}
if (n < 21) {
return factorial(n);
}
return Math.floor(Math.exp(factorialLog(n)) + 0.5);
}
/**
* Returns the natural logarithm of n!.
* <p>
* <Strong>Preconditions:
* <ul>
* <li> n >= 0 (otherwise
* <code>IllegalArgumentException is thrown)
* </ul>
*
* @param n argument
* @return <code>n!
* @throws IllegalArgumentException if preconditions are not met.
*/
public static double factorialLog(final int n) {
if (n < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"must have n >= 0 for n!, got n = {0}",
n);
}
if (n < 21) {
return Math.log(factorial(n));
}
double logSum = 0;
for (int i = 2; i <= n; i++) {
logSum += Math.log(i);
}
return logSum;
}
/**
* <p>
* Gets the greatest common divisor of the absolute value of two numbers,
* using the "binary gcd" method which avoids division and modulo
* operations. See Knuth 4.5.2 algorithm B. This algorithm is due to Josef
* Stein (1961).
* </p>
* Special cases:
* <ul>
* <li>The invocations
* <code>gcd(Integer.MIN_VALUE, Integer.MIN_VALUE),
* <code>gcd(Integer.MIN_VALUE, 0) and
* <code>gcd(0, Integer.MIN_VALUE) throw an
* <code>ArithmeticException, because the result would be 2^31, which
* is too large for an int value.</li>
* <li>The result of gcd(x, x), gcd(0, x) and
* <code>gcd(x, 0) is the absolute value of x, except
* for the special cases above.
* <li>The invocation gcd(0, 0) is the only one which returns
* <code>0.
* </ul>
*
* @param p any number
* @param q any number
* @return the greatest common divisor, never negative
* @throws ArithmeticException if the result cannot be represented as a
* nonnegative int value
* @since 1.1
*/
public static int gcd(final int p, final int q) {
int u = p;
int v = q;
if ((u == 0) || (v == 0)) {
if ((u == Integer.MIN_VALUE) || (v == Integer.MIN_VALUE)) {
throw MathRuntimeException.createArithmeticException(
"overflow: gcd({0}, {1}) is 2^31",
p, q);
}
return Math.abs(u) + Math.abs(v);
}
// keep u and v negative, as negative integers range down to
// -2^31, while positive numbers can only be as large as 2^31-1
// (i.e. we can't necessarily negate a negative number without
// overflow)
/* assert u!=0 && v!=0; */
if (u > 0) {
u = -u;
} // make u negative
if (v > 0) {
v = -v;
} // make v negative
// B1. [Find power of 2]
int k = 0;
while ((u & 1) == 0 && (v & 1) == 0 && k < 31) { // while u and v are
// both even...
u /= 2;
v /= 2;
k++; // cast out twos.
}
if (k == 31) {
throw MathRuntimeException.createArithmeticException(
"overflow: gcd({0}, {1}) is 2^31",
p, q);
}
// B2. Initialize: u and v have been divided by 2^k and at least
// one is odd.
int t = ((u & 1) == 1) ? v : -(u / 2)/* B3 */;
// t negative: u was odd, v may be even (t replaces v)
// t positive: u was even, v is odd (t replaces u)
do {
/* assert u<0 && v<0; */
// B4/B3: cast out twos from t.
while ((t & 1) == 0) { // while t is even..
t /= 2; // cast out twos
}
// B5 [reset max(u,v)]
if (t > 0) {
u = -t;
} else {
v = t;
}
// B6/B3. at this point both u and v should be odd.
t = (v - u) / 2;
// |u| larger: t positive (replace u)
// |v| larger: t negative (replace v)
} while (t != 0);
return -u * (1 << k); // gcd is u*2^k
}
/**
* <p>
* Gets the greatest common divisor of the absolute value of two numbers,
* using the "binary gcd" method which avoids division and modulo
* operations. See Knuth 4.5.2 algorithm B. This algorithm is due to Josef
* Stein (1961).
* </p>
* Special cases:
* <ul>
* <li>The invocations
* <code>gcd(Long.MIN_VALUE, Long.MIN_VALUE),
* <code>gcd(Long.MIN_VALUE, 0L) and
* <code>gcd(0L, Long.MIN_VALUE) throw an
* <code>ArithmeticException, because the result would be 2^63, which
* is too large for a long value.</li>
* <li>The result of gcd(x, x), gcd(0L, x) and
* <code>gcd(x, 0L) is the absolute value of x, except
* for the special cases above.
* <li>The invocation gcd(0L, 0L) is the only one which returns
* <code>0L.
* </ul>
*
* @param p any number
* @param q any number
* @return the greatest common divisor, never negative
* @throws ArithmeticException if the result cannot be represented as a nonnegative long
* value
* @since 2.1
*/
public static long gcd(final long p, final long q) {
long u = p;
long v = q;
if ((u == 0) || (v == 0)) {
if ((u == Long.MIN_VALUE) || (v == Long.MIN_VALUE)){
throw MathRuntimeException.createArithmeticException(
"overflow: gcd({0}, {1}) is 2^63",
p, q);
}
return Math.abs(u) + Math.abs(v);
}
// keep u and v negative, as negative integers range down to
// -2^63, while positive numbers can only be as large as 2^63-1
// (i.e. we can't necessarily negate a negative number without
// overflow)
/* assert u!=0 && v!=0; */
if (u > 0) {
u = -u;
} // make u negative
if (v > 0) {
v = -v;
} // make v negative
// B1. [Find power of 2]
int k = 0;
while ((u & 1) == 0 && (v & 1) == 0 && k < 63) { // while u and v are
// both even...
u /= 2;
v /= 2;
k++; // cast out twos.
}
if (k == 63) {
throw MathRuntimeException.createArithmeticException(
"overflow: gcd({0}, {1}) is 2^63",
p, q);
}
// B2. Initialize: u and v have been divided by 2^k and at least
// one is odd.
long t = ((u & 1) == 1) ? v : -(u / 2)/* B3 */;
// t negative: u was odd, v may be even (t replaces v)
// t positive: u was even, v is odd (t replaces u)
do {
/* assert u<0 && v<0; */
// B4/B3: cast out twos from t.
while ((t & 1) == 0) { // while t is even..
t /= 2; // cast out twos
}
// B5 [reset max(u,v)]
if (t > 0) {
u = -t;
} else {
v = t;
}
// B6/B3. at this point both u and v should be odd.
t = (v - u) / 2;
// |u| larger: t positive (replace u)
// |v| larger: t negative (replace v)
} while (t != 0);
return -u * (1L << k); // gcd is u*2^k
}
/**
* Returns an integer hash code representing the given double value.
*
* @param value the value to be hashed
* @return the hash code
*/
public static int hash(double value) {
return new Double(value).hashCode();
}
/**
* Returns an integer hash code representing the given double array.
*
* @param value the value to be hashed (may be null)
* @return the hash code
* @since 1.2
*/
public static int hash(double[] value) {
return Arrays.hashCode(value);
}
/**
* For a byte value x, this method returns (byte)(+1) if x >= 0 and
* (byte)(-1) if x < 0.
*
* @param x the value, a byte
* @return (byte)(+1) or (byte)(-1), depending on the sign of x
*/
public static byte indicator(final byte x) {
return (x >= ZB) ? PB : NB;
}
/**
* For a double precision value x, this method returns +1.0 if x >= 0 and
* -1.0 if x < 0. Returns if x is
* <code>NaN.
*
* @param x the value, a double
* @return +1.0 or -1.0, depending on the sign of x
*/
public static double indicator(final double x) {
if (Double.isNaN(x)) {
return Double.NaN;
}
return (x >= 0.0) ? 1.0 : -1.0;
}
/**
* For a float value x, this method returns +1.0F if x >= 0 and -1.0F if x <
* 0. Returns <code>NaN if x is NaN.
*
* @param x the value, a float
* @return +1.0F or -1.0F, depending on the sign of x
*/
public static float indicator(final float x) {
if (Float.isNaN(x)) {
return Float.NaN;
}
return (x >= 0.0F) ? 1.0F : -1.0F;
}
/**
* For an int value x, this method returns +1 if x >= 0 and -1 if x < 0.
*
* @param x the value, an int
* @return +1 or -1, depending on the sign of x
*/
public static int indicator(final int x) {
return (x >= 0) ? 1 : -1;
}
/**
* For a long value x, this method returns +1L if x >= 0 and -1L if x < 0.
*
* @param x the value, a long
* @return +1L or -1L, depending on the sign of x
*/
public static long indicator(final long x) {
return (x >= 0L) ? 1L : -1L;
}
/**
* For a short value x, this method returns (short)(+1) if x >= 0 and
* (short)(-1) if x < 0.
*
* @param x the value, a short
* @return (short)(+1) or (short)(-1), depending on the sign of x
*/
public static short indicator(final short x) {
return (x >= ZS) ? PS : NS;
}
/**
* <p>
* Returns the least common multiple of the absolute value of two numbers,
* using the formula <code>lcm(a,b) = (a / gcd(a,b)) * b.
* </p>
* Special cases:
* <ul>
* <li>The invocations lcm(Integer.MIN_VALUE, n) and
* <code>lcm(n, Integer.MIN_VALUE), where abs(n) is a
* power of 2, throw an <code>ArithmeticException, because the result
* would be 2^31, which is too large for an int value.</li>
* <li>The result of lcm(0, x) and lcm(x, 0) is
* <code>0 for any x.
* </ul>
*
* @param a any number
* @param b any number
* @return the least common multiple, never negative
* @throws ArithmeticException
* if the result cannot be represented as a nonnegative int
* value
* @since 1.1
*/
public static int lcm(int a, int b) {
if (a==0 || b==0){
return 0;
}
int lcm = Math.abs(mulAndCheck(a / gcd(a, b), b));
if (lcm == Integer.MIN_VALUE) {
throw MathRuntimeException.createArithmeticException(
"overflow: lcm({0}, {1}) is 2^31",
a, b);
}
return lcm;
}
/**
* <p>
* Returns the least common multiple of the absolute value of two numbers,
* using the formula <code>lcm(a,b) = (a / gcd(a,b)) * b.
* </p>
* Special cases:
* <ul>
* <li>The invocations lcm(Long.MIN_VALUE, n) and
* <code>lcm(n, Long.MIN_VALUE), where abs(n) is a
* power of 2, throw an <code>ArithmeticException, because the result
* would be 2^63, which is too large for an int value.</li>
* <li>The result of lcm(0L, x) and lcm(x, 0L) is
* <code>0L for any x.
* </ul>
*
* @param a any number
* @param b any number
* @return the least common multiple, never negative
* @throws ArithmeticException if the result cannot be represented as a nonnegative long
* value
* @since 2.1
*/
public static long lcm(long a, long b) {
if (a==0 || b==0){
return 0;
}
long lcm = Math.abs(mulAndCheck(a / gcd(a, b), b));
if (lcm == Long.MIN_VALUE){
throw MathRuntimeException.createArithmeticException(
"overflow: lcm({0}, {1}) is 2^63",
a, b);
}
return lcm;
}
/**
* <p>Returns the
* <a href="http://mathworld.wolfram.com/Logarithm.html">logarithm
* for base <code>b of x.
* </p>
* <p>Returns NaN if either argument is negative. If
* <code>base is 0 and x is positive, 0 is returned.
* If <code>base is positive and x is 0,
* <code>Double.NEGATIVE_INFINITY is returned. If both arguments
* are 0, the result is <code>NaN.
*
* @param base the base of the logarithm, must be greater than 0
* @param x argument, must be greater than 0
* @return the value of the logarithm - the number y such that base^y = x.
* @since 1.2
*/
public static double log(double base, double x) {
return Math.log(x)/Math.log(base);
}
/**
* Multiply two integers, checking for overflow.
*
* @param x a factor
* @param y a factor
* @return the product <code>x*y
* @throws ArithmeticException if the result can not be represented as an
* int
* @since 1.1
*/
public static int mulAndCheck(int x, int y) {
long m = ((long)x) * ((long)y);
if (m < Integer.MIN_VALUE || m > Integer.MAX_VALUE) {
throw new ArithmeticException("overflow: mul");
}
return (int)m;
}
/**
* Multiply two long integers, checking for overflow.
*
* @param a first value
* @param b second value
* @return the product <code>a * b
* @throws ArithmeticException if the result can not be represented as an
* long
* @since 1.2
*/
public static long mulAndCheck(long a, long b) {
long ret;
String msg = "overflow: multiply";
if (a > b) {
// use symmetry to reduce boundary cases
ret = mulAndCheck(b, a);
} else {
if (a < 0) {
if (b < 0) {
// check for positive overflow with negative a, negative b
if (a >= Long.MAX_VALUE / b) {
ret = a * b;
} else {
throw new ArithmeticException(msg);
}
} else if (b > 0) {
// check for negative overflow with negative a, positive b
if (Long.MIN_VALUE / b <= a) {
ret = a * b;
} else {
throw new ArithmeticException(msg);
}
} else {
// assert b == 0
ret = 0;
}
} else if (a > 0) {
// assert a > 0
// assert b > 0
// check for positive overflow with positive a, positive b
if (a <= Long.MAX_VALUE / b) {
ret = a * b;
} else {
throw new ArithmeticException(msg);
}
} else {
// assert a == 0
ret = 0;
}
}
return ret;
}
/**
* Get the next machine representable number after a number, moving
* in the direction of another number.
* <p>
* If <code>direction is greater than or equal tod,
* the smallest machine representable number strictly greater than
* <code>d is returned; otherwise the largest representable number
* strictly less than <code>d is returned.
* <p>
* If <code>d is NaN or Infinite, it is returned unchanged.
*
* @param d base number
* @param direction (the only important thing is whether
* direction is greater or smaller than d)
* @return the next machine representable number in the specified direction
* @since 1.2
*/
public static double nextAfter(double d, double direction) {
// handling of some important special cases
if (Double.isNaN(d) || Double.isInfinite(d)) {
return d;
} else if (d == 0) {
return (direction < 0) ? -Double.MIN_VALUE : Double.MIN_VALUE;
}
// special cases MAX_VALUE to infinity and MIN_VALUE to 0
// are handled just as normal numbers
// split the double in raw components
long bits = Double.doubleToLongBits(d);
long sign = bits & 0x8000000000000000L;
long exponent = bits & 0x7ff0000000000000L;
long mantissa = bits & 0x000fffffffffffffL;
if (d * (direction - d) >= 0) {
// we should increase the mantissa
if (mantissa == 0x000fffffffffffffL) {
return Double.longBitsToDouble(sign |
(exponent + 0x0010000000000000L));
} else {
return Double.longBitsToDouble(sign |
exponent | (mantissa + 1));
}
} else {
// we should decrease the mantissa
if (mantissa == 0L) {
return Double.longBitsToDouble(sign |
(exponent - 0x0010000000000000L) |
0x000fffffffffffffL);
} else {
return Double.longBitsToDouble(sign |
exponent | (mantissa - 1));
}
}
}
/**
* Scale a number by 2<sup>scaleFactor.
* <p>If d is 0 or NaN or Infinite, it is returned unchanged.
*
* @param d base number
* @param scaleFactor power of two by which d sould be multiplied
* @return d × 2<sup>scaleFactor
* @since 2.0
*/
public static double scalb(final double d, final int scaleFactor) {
// handling of some important special cases
if ((d == 0) || Double.isNaN(d) || Double.isInfinite(d)) {
return d;
}
// split the double in raw components
final long bits = Double.doubleToLongBits(d);
final long exponent = bits & 0x7ff0000000000000L;
final long rest = bits & 0x800fffffffffffffL;
// shift the exponent
final long newBits = rest | (exponent + (((long) scaleFactor) << 52));
return Double.longBitsToDouble(newBits);
}
/**
* Normalize an angle in a 2&pi wide interval around a center value.
* <p>This method has three main uses:
* <ul>
* <li>normalize an angle between 0 and 2?:
* <code>a = MathUtils.normalizeAngle(a, Math.PI);
* <li>normalize an angle between -? and +?
* <code>a = MathUtils.normalizeAngle(a, 0.0);
* <li>compute the angle between two defining angular positions:
* <code>angle = MathUtils.normalizeAngle(end, start) - start;
* </ul>
* <p>Note that due to numerical accuracy and since ? cannot be represented
* exactly, the result interval is <em>closed, it cannot be half-closed
* as would be more satisfactory in a purely mathematical view.</p>
* @param a angle to normalize
* @param center center of the desired 2? interval for the result
* @return a-2k? with integer k and center-? <= a-2k? <= center+?
* @since 1.2
*/
public static double normalizeAngle(double a, double center) {
return a - TWO_PI * Math.floor((a + Math.PI - center) / TWO_PI);
}
/**
* <p>Normalizes an array to make it sum to a specified value.
* Returns the result of the transformation <pre>
* x |-> x * normalizedSum / sum
* </pre>
* applied to each non-NaN element x of the input array, where sum is the
* sum of the non-NaN entries in the input array.</p>
*
* <p>Throws IllegalArgumentException if normalizedSum is infinite
* or NaN and ArithmeticException if the input array contains any infinite elements
* or sums to 0</p>
*
* <p>Ignores (i.e., copies unchanged to the output array) NaNs in the input array.
*
* @param values input array to be normalized
* @param normalizedSum target sum for the normalized array
* @return normalized array
* @throws ArithmeticException if the input array contains infinite elements or sums to zero
* @throws IllegalArgumentException if the target sum is infinite or NaN
* @since 2.1
*/
public static double[] normalizeArray(double[] values, double normalizedSum)
throws ArithmeticException, IllegalArgumentException {
if (Double.isInfinite(normalizedSum)) {
throw MathRuntimeException.createIllegalArgumentException(
"Cannot normalize to an infinite value");
}
if (Double.isNaN(normalizedSum)) {
throw MathRuntimeException.createIllegalArgumentException(
"Cannot normalize to NaN");
}
double sum = 0d;
final int len = values.length;
double[] out = new double[len];
for (int i = 0; i < len; i++) {
if (Double.isInfinite(values[i])) {
throw MathRuntimeException.createArithmeticException(
"Array contains an infinite element, {0} at index {1}", values[i], i);
}
if (!Double.isNaN(values[i])) {
sum += values[i];
}
}
if (sum == 0) {
throw MathRuntimeException.createArithmeticException(
"Array sums to zero");
}
for (int i = 0; i < len; i++) {
if (Double.isNaN(values[i])) {
out[i] = Double.NaN;
} else {
out[i] = values[i] * normalizedSum / sum;
}
}
return out;
}
/**
* Round the given value to the specified number of decimal places. The
* value is rounded using the {@link BigDecimal#ROUND_HALF_UP} method.
*
* @param x the value to round.
* @param scale the number of digits to the right of the decimal point.
* @return the rounded value.
* @since 1.1
*/
public static double round(double x, int scale) {
return round(x, scale, BigDecimal.ROUND_HALF_UP);
}
/**
* Round the given value to the specified number of decimal places. The
* value is rounded using the given method which is any method defined in
* {@link BigDecimal}.
*
* @param x the value to round.
* @param scale the number of digits to the right of the decimal point.
* @param roundingMethod the rounding method as defined in
* {@link BigDecimal}.
* @return the rounded value.
* @since 1.1
*/
public static double round(double x, int scale, int roundingMethod) {
try {
return (new BigDecimal
(Double.toString(x))
.setScale(scale, roundingMethod))
.doubleValue();
} catch (NumberFormatException ex) {
if (Double.isInfinite(x)) {
return x;
} else {
return Double.NaN;
}
}
}
/**
* Round the given value to the specified number of decimal places. The
* value is rounding using the {@link BigDecimal#ROUND_HALF_UP} method.
*
* @param x the value to round.
* @param scale the number of digits to the right of the decimal point.
* @return the rounded value.
* @since 1.1
*/
public static float round(float x, int scale) {
return round(x, scale, BigDecimal.ROUND_HALF_UP);
}
/**
* Round the given value to the specified number of decimal places. The
* value is rounded using the given method which is any method defined in
* {@link BigDecimal}.
*
* @param x the value to round.
* @param scale the number of digits to the right of the decimal point.
* @param roundingMethod the rounding method as defined in
* {@link BigDecimal}.
* @return the rounded value.
* @since 1.1
*/
public static float round(float x, int scale, int roundingMethod) {
float sign = indicator(x);
float factor = (float)Math.pow(10.0f, scale) * sign;
return (float)roundUnscaled(x * factor, sign, roundingMethod) / factor;
}
/**
* Round the given non-negative, value to the "nearest" integer. Nearest is
* determined by the rounding method specified. Rounding methods are defined
* in {@link BigDecimal}.
*
* @param unscaled the value to round.
* @param sign the sign of the original, scaled value.
* @param roundingMethod the rounding method as defined in
* {@link BigDecimal}.
* @return the rounded value.
* @since 1.1
*/
private static double roundUnscaled(double unscaled, double sign,
int roundingMethod) {
switch (roundingMethod) {
case BigDecimal.ROUND_CEILING :
if (sign == -1) {
unscaled = Math.floor(nextAfter(unscaled, Double.NEGATIVE_INFINITY));
} else {
unscaled = Math.ceil(nextAfter(unscaled, Double.POSITIVE_INFINITY));
}
break;
case BigDecimal.ROUND_DOWN :
unscaled = Math.floor(nextAfter(unscaled, Double.NEGATIVE_INFINITY));
break;
case BigDecimal.ROUND_FLOOR :
if (sign == -1) {
unscaled = Math.ceil(nextAfter(unscaled, Double.POSITIVE_INFINITY));
} else {
unscaled = Math.floor(nextAfter(unscaled, Double.NEGATIVE_INFINITY));
}
break;
case BigDecimal.ROUND_HALF_DOWN : {
unscaled = nextAfter(unscaled, Double.NEGATIVE_INFINITY);
double fraction = unscaled - Math.floor(unscaled);
if (fraction > 0.5) {
unscaled = Math.ceil(unscaled);
} else {
unscaled = Math.floor(unscaled);
}
break;
}
case BigDecimal.ROUND_HALF_EVEN : {
double fraction = unscaled - Math.floor(unscaled);
if (fraction > 0.5) {
unscaled = Math.ceil(unscaled);
} else if (fraction < 0.5) {
unscaled = Math.floor(unscaled);
} else {
// The following equality test is intentional and needed for rounding purposes
if (Math.floor(unscaled) / 2.0 == Math.floor(Math
.floor(unscaled) / 2.0)) { // even
unscaled = Math.floor(unscaled);
} else { // odd
unscaled = Math.ceil(unscaled);
}
}
break;
}
case BigDecimal.ROUND_HALF_UP : {
unscaled = nextAfter(unscaled, Double.POSITIVE_INFINITY);
double fraction = unscaled - Math.floor(unscaled);
if (fraction >= 0.5) {
unscaled = Math.ceil(unscaled);
} else {
unscaled = Math.floor(unscaled);
}
break;
}
case BigDecimal.ROUND_UNNECESSARY :
if (unscaled != Math.floor(unscaled)) {
throw new ArithmeticException("Inexact result from rounding");
}
break;
case BigDecimal.ROUND_UP :
unscaled = Math.ceil(nextAfter(unscaled, Double.POSITIVE_INFINITY));
break;
default :
throw MathRuntimeException.createIllegalArgumentException(
"invalid rounding method {0}, valid methods: {1} ({2}), {3} ({4})," +
" {5} ({6}), {7} ({8}), {9} ({10}), {11} ({12}), {13} ({14}), {15} ({16})",
roundingMethod,
"ROUND_CEILING", BigDecimal.ROUND_CEILING,
"ROUND_DOWN", BigDecimal.ROUND_DOWN,
"ROUND_FLOOR", BigDecimal.ROUND_FLOOR,
"ROUND_HALF_DOWN", BigDecimal.ROUND_HALF_DOWN,
"ROUND_HALF_EVEN", BigDecimal.ROUND_HALF_EVEN,
"ROUND_HALF_UP", BigDecimal.ROUND_HALF_UP,
"ROUND_UNNECESSARY", BigDecimal.ROUND_UNNECESSARY,
"ROUND_UP", BigDecimal.ROUND_UP);
}
return unscaled;
}
/**
* Returns the <a href="http://mathworld.wolfram.com/Sign.html"> sign
* for byte value <code>x.
* <p>
* For a byte value x, this method returns (byte)(+1) if x > 0, (byte)(0) if
* x = 0, and (byte)(-1) if x < 0.
* for double precision <code>x.
* <p>
* For a double value <code>x, this method returns
* <code>+1.0 if x > 0, 0.0 if
* <code>x = 0.0, and -1.0 if x < 0.
* Returns <code>NaN if x is NaN.
*
* @param x the value, a double
* @return +1.0, 0.0, or -1.0, depending on the sign of x
*/
public static double sign(final double x) {
if (Double.isNaN(x)) {
return Double.NaN;
}
return (x == 0.0) ? 0.0 : (x > 0.0) ? 1.0 : -1.0;
}
/**
* Returns the <a href="http://mathworld.wolfram.com/Sign.html"> sign
* for float value <code>x.
* <p>
* For a float value x, this method returns +1.0F if x > 0, 0.0F if x =
* 0.0F, and -1.0F if x < 0. Returns if x
* is <code>NaN.
*
* @param x the value, a float
* @return +1.0F, 0.0F, or -1.0F, depending on the sign of x
*/
public static float sign(final float x) {
if (Float.isNaN(x)) {
return Float.NaN;
}
return (x == 0.0F) ? 0.0F : (x > 0.0F) ? 1.0F : -1.0F;
}
/**
* Returns the <a href="http://mathworld.wolfram.com/Sign.html"> sign
* for int value <code>x.
* <p>
* For an int value x, this method returns +1 if x > 0, 0 if x = 0, and -1
* if x < 0.
* for long value <code>x.
* <p>
* For a long value x, this method returns +1L if x > 0, 0L if x = 0, and
* -1L if x < 0.
* for short value <code>x.
* <p>
* For a short value x, this method returns (short)(+1) if x > 0, (short)(0)
* if x = 0, and (short)(-1) if x < 0.
* @throws ArithmeticException if the result can not be represented as an
* int
* @since 1.1
*/
public static int subAndCheck(int x, int y) {
long s = (long)x - (long)y;
if (s < Integer.MIN_VALUE || s > Integer.MAX_VALUE) {
throw new ArithmeticException("overflow: subtract");
}
return (int)s;
}
/**
* Subtract two long integers, checking for overflow.
*
* @param a first value
* @param b second value
* @return the difference <code>a-b
* @throws ArithmeticException if the result can not be represented as an
* long
* @since 1.2
*/
public static long subAndCheck(long a, long b) {
long ret;
String msg = "overflow: subtract";
if (b == Long.MIN_VALUE) {
if (a < 0) {
ret = a - b;
} else {
throw new ArithmeticException(msg);
}
} else {
// use additive inverse
ret = addAndCheck(a, -b, msg);
}
return ret;
}
/**
* Raise an int to an int power.
* @param k number to raise
* @param e exponent (must be positive or null)
* @return k<sup>e
* @exception IllegalArgumentException if e is negative
*/
public static int pow(final int k, int e)
throws IllegalArgumentException {
if (e < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"cannot raise an integral value to a negative power ({0}^{1})",
k, e);
}
int result = 1;
int k2p = k;
while (e != 0) {
if ((e & 0x1) != 0) {
result *= k2p;
}
k2p *= k2p;
e = e >> 1;
}
return result;
}
/**
* Raise an int to a long power.
* @param k number to raise
* @param e exponent (must be positive or null)
* @return k<sup>e
* @exception IllegalArgumentException if e is negative
*/
public static int pow(final int k, long e)
throws IllegalArgumentException {
if (e < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"cannot raise an integral value to a negative power ({0}^{1})",
k, e);
}
int result = 1;
int k2p = k;
while (e != 0) {
if ((e & 0x1) != 0) {
result *= k2p;
}
k2p *= k2p;
e = e >> 1;
}
return result;
}
/**
* Raise a long to an int power.
* @param k number to raise
* @param e exponent (must be positive or null)
* @return k<sup>e
* @exception IllegalArgumentException if e is negative
*/
public static long pow(final long k, int e)
throws IllegalArgumentException {
if (e < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"cannot raise an integral value to a negative power ({0}^{1})",
k, e);
}
long result = 1l;
long k2p = k;
while (e != 0) {
if ((e & 0x1) != 0) {
result *= k2p;
}
k2p *= k2p;
e = e >> 1;
}
return result;
}
/**
* Raise a long to a long power.
* @param k number to raise
* @param e exponent (must be positive or null)
* @return k<sup>e
* @exception IllegalArgumentException if e is negative
*/
public static long pow(final long k, long e)
throws IllegalArgumentException {
if (e < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"cannot raise an integral value to a negative power ({0}^{1})",
k, e);
}
long result = 1l;
long k2p = k;
while (e != 0) {
if ((e & 0x1) != 0) {
result *= k2p;
}
k2p *= k2p;
e = e >> 1;
}
return result;
}
/**
* Raise a BigInteger to an int power.
* @param k number to raise
* @param e exponent (must be positive or null)
* @return k<sup>e
* @exception IllegalArgumentException if e is negative
*/
public static BigInteger pow(final BigInteger k, int e)
throws IllegalArgumentException {
if (e < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"cannot raise an integral value to a negative power ({0}^{1})",
k, e);
}
return k.pow(e);
}
/**
* Raise a BigInteger to a long power.
* @param k number to raise
* @param e exponent (must be positive or null)
* @return k<sup>e
* @exception IllegalArgumentException if e is negative
*/
public static BigInteger pow(final BigInteger k, long e)
throws IllegalArgumentException {
if (e < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"cannot raise an integral value to a negative power ({0}^{1})",
k, e);
}
BigInteger result = BigInteger.ONE;
BigInteger k2p = k;
while (e != 0) {
if ((e & 0x1) != 0) {
result = result.multiply(k2p);
}
k2p = k2p.multiply(k2p);
e = e >> 1;
}
return result;
}
/**
* Raise a BigInteger to a BigInteger power.
* @param k number to raise
* @param e exponent (must be positive or null)
* @return k<sup>e
* @exception IllegalArgumentException if e is negative
*/
public static BigInteger pow(final BigInteger k, BigInteger e)
throws IllegalArgumentException {
if (e.compareTo(BigInteger.ZERO) < 0) {
throw MathRuntimeException.createIllegalArgumentException(
"cannot raise an integral value to a negative power ({0}^{1})",
k, e);
}
BigInteger result = BigInteger.ONE;
BigInteger k2p = k;
while (!BigInteger.ZERO.equals(e)) {
if (e.testBit(0)) {
result = result.multiply(k2p);
}
k2p = k2p.multiply(k2p);
e = e.shiftRight(1);
}
return result;
}
/**
* Calculates the L<sub>1 (sum of abs) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>1 distance between the two points
*/
public static double distance1(double[] p1, double[] p2) {
double sum = 0;
for (int i = 0; i < p1.length; i++) {
sum += Math.abs(p1[i] - p2[i]);
}
return sum;
}
/**
* Calculates the L<sub>1 (sum of abs) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>1 distance between the two points
*/
public static int distance1(int[] p1, int[] p2) {
int sum = 0;
for (int i = 0; i < p1.length; i++) {
sum += Math.abs(p1[i] - p2[i]);
}
return sum;
}
/**
* Calculates the L<sub>2 (Euclidean) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>2 distance between the two points
*/
public static double distance(double[] p1, double[] p2) {
double sum = 0;
for (int i = 0; i < p1.length; i++) {
final double dp = p1[i] - p2[i];
sum += dp * dp;
}
return Math.sqrt(sum);
}
/**
* Calculates the L<sub>2 (Euclidean) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>2 distance between the two points
*/
public static double distance(int[] p1, int[] p2) {
double sum = 0;
for (int i = 0; i < p1.length; i++) {
final double dp = p1[i] - p2[i];
sum += dp * dp;
}
return Math.sqrt(sum);
}
/**
* Calculates the L<sub>? (max of abs) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>? distance between the two points
*/
public static double distanceInf(double[] p1, double[] p2) {
double max = 0;
for (int i = 0; i < p1.length; i++) {
max = Math.max(max, Math.abs(p1[i] - p2[i]));
}
return max;
}
/**
* Calculates the L<sub>? (max of abs) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>? distance between the two points
*/
public static int distanceInf(int[] p1, int[] p2) {
int max = 0;
for (int i = 0; i < p1.length; i++) {
max = Math.max(max, Math.abs(p1[i] - p2[i]));
}
return max;
}
/**
* Checks that the given array is sorted.
*
* @param val Values
* @param dir Order direction (-1 for decreasing, 1 for increasing)
* @param strict Whether the order should be strict
* @throws IllegalArgumentException if the array is not sorted.
*/
public static void checkOrder(double[] val, int dir, boolean strict) {
double previous = val[0];
int max = val.length;
for (int i = 1; i < max; i++) {
if (dir > 0) {
if (strict) {
if (val[i] <= previous) {
throw MathRuntimeException.createIllegalArgumentException("points {0} and {1} are not strictly increasing ({2} >= {3})",
i - 1, i, previous, val[i]);
}
} else {
if (val[i] < previous) {
throw MathRuntimeException.createIllegalArgumentException("points {0} and {1} are not increasing ({2} > {3})",
i - 1, i, previous, val[i]);
}
}
} else {
if (strict) {
if (val[i] >= previous) {
throw MathRuntimeException.createIllegalArgumentException("points {0} and {1} are not strictly decreasing ({2} <= {3})",
i - 1, i, previous, val[i]);
}
} else {
if (val[i] > previous) {
throw MathRuntimeException.createIllegalArgumentException("points {0} and {1} are not decreasing ({2} < {3})",
i - 1, i, previous, val[i]);
}
}
}
previous = val[i];
}
}
}
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