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https://issues.apache.org/jira/browse/MATH-951?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Charles Cooper updated MATH-951:
--------------------------------
Description:
Between 40-50% faster than both current implementation and
java.lang.Math.copySign by my (sloppy) benchmark. Patch attached.
was:
Between 40-50% faster than both current implementation and
java.lang.Math.copySign by my (sloppy) benchmark. Patch below.
Index: src/main/java/org/apache/commons/math3/util/FastMath.java
===================================================================
--- src/main/java/org/apache/commons/math3/util/FastMath.java (revision
1458590)
+++ src/main/java/org/apache/commons/math3/util/FastMath.java (working copy)
@@ -3632,9 +3632,8 @@
public static double copySign(double magnitude, double sign){
long m = Double.doubleToLongBits(magnitude);
long s = Double.doubleToLongBits(sign);
- if ((m >= 0 && s >= 0) || (m < 0 && s < 0)) { // Sign is currently OK
+ if ((m^s) >= 0) // have same sign
return magnitude;
- }
return -magnitude; // flip sign
}
@@ -3649,9 +3648,8 @@
public static float copySign(float magnitude, float sign){
int m = Float.floatToIntBits(magnitude);
int s = Float.floatToIntBits(sign);
- if ((m >= 0 && s >= 0) || (m < 0 && s < 0)) { // Sign is currently OK
+ if ((m^s) >= 0)
return magnitude;
- }
return -magnitude; // flip sign
}
> Patch: Faster implementation of double
> org.apache.commons.math3.FastMath.copySign(double, double)
> -------------------------------------------------------------------------------------------------
>
> Key: MATH-951
> URL: https://issues.apache.org/jira/browse/MATH-951
> Project: Commons Math
> Issue Type: Improvement
> Affects Versions: 3.2
> Environment: java version "1.6.0_27"
> OpenJDK Runtime Environment (IcedTea6 1.12.3) (6b27-1.12.3-1)
> OpenJDK 64-Bit Server VM (build 20.0-b12, mixed mode)
> Linux debian 3.2.0-4-amd64 #2 SMP Wed Jan 2 01:41:29 PST 2013 x86_64 GNU/Linux
> Intel(R) Core(TM) i5-2500 CPU @ 3.30GHz
> Reporter: Charles Cooper
> Priority: Minor
> Labels: patch, performance
> Fix For: 3.2
>
> Original Estimate: 0h
> Remaining Estimate: 0h
>
> Between 40-50% faster than both current implementation and
> java.lang.Math.copySign by my (sloppy) benchmark. Patch attached.
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