net.openhft.chronicle.hash.impl.util.math.Precision Maven / Gradle / Ivy
/*
* Copyright 2012-2018 Chronicle Map Contributors
* Copyright 2001-2015 The Apache Software Foundation
* Copyright 2010-2012 CS Systèmes d'Information
*
* 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 net.openhft.chronicle.hash.impl.util.math;
class Precision {
/**
* Offset to order signed double numbers lexicographically.
*/
private static final long SGN_MASK = 0x8000000000000000L;
/**
* Positive zero bits.
*/
private static final long POSITIVE_ZERO_DOUBLE_BITS = Double.doubleToRawLongBits(+0.0);
/**
* Negative zero bits.
*/
private static final long NEGATIVE_ZERO_DOUBLE_BITS = Double.doubleToRawLongBits(-0.0);
/**
* Returns {@code true} if there is no double value strictly between the
* arguments or the difference between them is within the range of allowed
* error (inclusive).
*
* @param x First value.
* @param y Second value.
* @param eps Amount of allowed absolute error.
* @return {@code true} if the values are two adjacent floating point
* numbers or they are within range of each other.
*/
public static boolean isEquals(double x, double y, double eps) {
return isEquals(x, y, 1) || Math.abs(y - x) <= eps;
}
/**
* Returns true if both arguments are equal or within the range of allowed
* error (inclusive).
*
* Two float numbers are considered equal if there are {@code (maxUlps - 1)}
* (or fewer) floating point numbers between them, i.e. two adjacent
* floating point numbers are considered equal.
*
*
* Adapted from
* Bruce Dawson
*
*
* @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 fewer than {@code maxUlps} floating
* point values between {@code x} and {@code y}.
*/
public static boolean isEquals(final double x, final double y, final int maxUlps) {
final long xInt = Double.doubleToRawLongBits(x);
final long yInt = Double.doubleToRawLongBits(y);
final boolean isEqual;
if (((xInt ^ yInt) & SGN_MASK) == 0L) {
// number have same sign, there is no risk of overflow
isEqual = Math.abs(xInt - yInt) <= maxUlps;
} else {
// number have opposite signs, take care of overflow
final long deltaPlus;
final long deltaMinus;
if (xInt < yInt) {
deltaPlus = yInt - POSITIVE_ZERO_DOUBLE_BITS;
deltaMinus = xInt - NEGATIVE_ZERO_DOUBLE_BITS;
} else {
deltaPlus = xInt - POSITIVE_ZERO_DOUBLE_BITS;
deltaMinus = yInt - NEGATIVE_ZERO_DOUBLE_BITS;
}
if (deltaPlus > maxUlps) {
isEqual = false;
} else {
isEqual = deltaMinus <= (maxUlps - deltaPlus);
}
}
return isEqual && !Double.isNaN(x) && !Double.isNaN(y);
}
}