Author: luc
Date: Mon Mar 25 10:46:42 2013
New Revision: 1460604
URL: http://svn.apache.org/r1460604
Log:
Improved speed of FastMath.abs methods, by removing branching.
JIRA: MATH-954
Modified:
commons/proper/math/trunk/src/changes/changes.xml
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/util/FastMath.java
Modified: commons/proper/math/trunk/src/changes/changes.xml
URL:
http://svn.apache.org/viewvc/commons/proper/math/trunk/src/changes/changes.xml?rev=1460604&r1=1460603&r2=1460604&view=diff
==============================================================================
--- commons/proper/math/trunk/src/changes/changes.xml (original)
+++ commons/proper/math/trunk/src/changes/changes.xml Mon Mar 25 10:46:42 2013
@@ -55,10 +55,13 @@ This is a minor release: It combines bug
Changes to existing features were made in a backwards-compatible
way such as to allow drop-in replacement of the v3.1[.1] JAR file.
">
+ <action dev="luc" type="update" issue="MATH-954" due-to="Charles Cooper">
+ Improved speed of FastMath.abs methods for all signatures, by removing
branching.
+ </action>
<action dev="luc" type="update" issue="MATH-953" due-to="Charles Cooper">
Improved speed of several FastMath methods.
</action>
- <action dev="luc" type="fix" issue="MATH-934">
+ <action dev="luc" type="fix" issue="MATH-934">
Fixed Complex.reciprocal() for zero argument.
</action>
<action dev="luc" type="update" issue="MATH-951" due-to="Charles Cooper">
Modified:
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/util/FastMath.java
URL:
http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math3/util/FastMath.java?rev=1460604&r1=1460603&r2=1460604&view=diff
==============================================================================
---
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/util/FastMath.java
(original)
+++
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/util/FastMath.java
Mon Mar 25 10:46:42 2013
@@ -2987,7 +2987,8 @@ public class FastMath {
* @return abs(x)
*/
public static int abs(final int x) {
- return (x < 0) ? -x : x;
+ final int i = x >>> 31;
+ return (x ^ (~i + 1)) + i;
}
/**
@@ -2996,7 +2997,12 @@ public class FastMath {
* @return abs(x)
*/
public static long abs(final long x) {
- return (x < 0l) ? -x : x;
+ final long l = x >>> 63;
+ // l is one if x negative zero else
+ // ~l+1 is zero if x is positive, -1 if x is negative
+ // x^(~l+1) is x is x is positive, ~x if x is negative
+ // add around
+ return (x ^ (~l + 1)) + l;
}
/**
@@ -3005,7 +3011,10 @@ public class FastMath {
* @return abs(x)
*/
public static float abs(final float x) {
- return (x < 0.0f) ? -x : (x == 0.0f) ? 0.0f : x; // -0.0 => +0.0
+ if ((Float.floatToRawIntBits(x) & Integer.MIN_VALUE) == 0) {
+ return x;
+ }
+ return -x;
}
/**
@@ -3014,7 +3023,10 @@ public class FastMath {
* @return abs(x)
*/
public static double abs(double x) {
- return (x < 0.0) ? -x : (x == 0.0) ? 0.0 : x; // -0.0 => +0.0
+ if ((Double.doubleToRawLongBits(x) & Long.MIN_VALUE) == 0) {
+ return x;
+ }
+ return -x;
}
/**
