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8022181: Tune algorithm crossover thresholds in BigInteger

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Change multiplication, squaring, division, and base conversion thresholds to values which retain performance improvement in most cases but with a a lower overall risk of regression.

Reviewed-by: darcy
This commit is contained in:
Brian Burkhalter 2013-12-03 12:25:32 -08:00
parent 4d33e16da1
commit 6c3fdefd1d
1 changed files with 6 additions and 6 deletions
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12
jdk/src/share/classes/java/math/BigInteger.java
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@ -215,7 +215,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
* Karatsuba multiplication will be used. This value is found
* experimentally to work well.
*/
private static final int KARATSUBA_THRESHOLD = 50;
private static final int KARATSUBA_THRESHOLD = 80;
/**
* The threshold value for using 3-way Toom-Cook multiplication.
@ -224,7 +224,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
* the mag arrays is greater than this threshold, then Toom-Cook
* multiplication will be used.
*/
private static final int TOOM_COOK_THRESHOLD = 75;
private static final int TOOM_COOK_THRESHOLD = 240;
/**
* The threshold value for using Karatsuba squaring. If the number
@ -232,7 +232,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
* Karatsuba squaring will be used. This value is found
* experimentally to work well.
*/
private static final int KARATSUBA_SQUARE_THRESHOLD = 90;
private static final int KARATSUBA_SQUARE_THRESHOLD = 128;
/**
* The threshold value for using Toom-Cook squaring. If the number
@ -240,7 +240,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
* Toom-Cook squaring will be used. This value is found
* experimentally to work well.
*/
private static final int TOOM_COOK_SQUARE_THRESHOLD = 140;
private static final int TOOM_COOK_SQUARE_THRESHOLD = 216;
/**
* The threshold value for using Burnikel-Ziegler division. If the number
@ -248,7 +248,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
* Burnikel-Ziegler division will be used. This value is found
* experimentally to work well.
*/
static final int BURNIKEL_ZIEGLER_THRESHOLD = 50;
static final int BURNIKEL_ZIEGLER_THRESHOLD = 80;
/**
* The threshold value for using Schoenhage recursive base conversion. If
@ -258,7 +258,7 @@ public class BigInteger extends Number implements Comparable<BigInteger> {
* relatively flat for thresholds between 2-25, so this choice may be
* varied within this range for very small effect.
*/
private static final int SCHOENHAGE_BASE_CONVERSION_THRESHOLD = 8;
private static final int SCHOENHAGE_BASE_CONVERSION_THRESHOLD = 20;
//Constructors