From: Robert Griesemer <gri@golang.org>
Date: Thu, 12 Jul 2012 21:19:09 +0000 (-0700)
Subject: mat/big: more optimal Karatsuba threshold
X-Git-Tag: go1.1rc2~2813
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=6a135a0894fff5bbb1885c27fd9eb41b9a2b4e51;p=gostls13.git

mat/big: more optimal Karatsuba threshold

benchmark           old ns/op    new ns/op    delta
BenchmarkHilbert      6253043      6267289   +0.23%
BenchmarkMul         45355940     39490633  -12.93%

R=r
CC=golang-dev
https://golang.org/cl/6355104
---

diff --git a/src/pkg/math/big/nat.go b/src/pkg/math/big/nat.go
index 04f5dfd8ba..85b9acc0f5 100644
--- a/src/pkg/math/big/nat.go
+++ b/src/pkg/math/big/nat.go
@@ -236,7 +236,7 @@ func karatsubaSub(z, x nat, n int) {
 // Operands that are shorter than karatsubaThreshold are multiplied using
 // "grade school" multiplication; for longer operands the Karatsuba algorithm
 // is used.
-var karatsubaThreshold int = 32 // computed by calibrate.go
+var karatsubaThreshold int = 40 // computed by calibrate.go
 
 // karatsuba multiplies x and y and leaves the result in z.
 // Both x and y must have the same length n and n must be a