mirror of
https://github.com/golang/go
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17eba6e6b7
Trivial merging of 5g, 6g, ... into go tool compile, and similarlly 5l, 6l, ... into go tool link. The files compile/main.go and link/main.go are new. Everything else in those directories is a move followed by change of imports and package name. This CL breaks the build. Manual fixups are in the next CL. See golang-dev thread titled "go tool compile, etc" for background. Change-Id: Id35ff5a5859ad9037c61275d637b1bd51df6828b Reviewed-on: https://go-review.googlesource.com/10287 Reviewed-by: Dave Cheney <dave@cheney.net> Reviewed-by: Rob Pike <r@golang.org>
89 lines
2.1 KiB
Go
89 lines
2.1 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This file prints execution times for the Mul benchmark
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// given different Karatsuba thresholds. The result may be
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// used to manually fine-tune the threshold constant. The
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// results are somewhat fragile; use repeated runs to get
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// a clear picture.
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// Usage: go test -run=TestCalibrate -calibrate
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package big
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import (
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"flag"
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"fmt"
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"testing"
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"time"
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)
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var calibrate = flag.Bool("calibrate", false, "run calibration test")
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func karatsubaLoad(b *testing.B) {
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BenchmarkMul(b)
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}
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// measureKaratsuba returns the time to run a Karatsuba-relevant benchmark
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// given Karatsuba threshold th.
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func measureKaratsuba(th int) time.Duration {
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th, karatsubaThreshold = karatsubaThreshold, th
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res := testing.Benchmark(karatsubaLoad)
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karatsubaThreshold = th
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return time.Duration(res.NsPerOp())
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}
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func computeThresholds() {
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fmt.Printf("Multiplication times for varying Karatsuba thresholds\n")
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fmt.Printf("(run repeatedly for good results)\n")
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// determine Tk, the work load execution time using basic multiplication
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Tb := measureKaratsuba(1e9) // th == 1e9 => Karatsuba multiplication disabled
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fmt.Printf("Tb = %10s\n", Tb)
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// thresholds
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th := 4
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th1 := -1
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th2 := -1
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var deltaOld time.Duration
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for count := -1; count != 0 && th < 128; count-- {
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// determine Tk, the work load execution time using Karatsuba multiplication
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Tk := measureKaratsuba(th)
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// improvement over Tb
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delta := (Tb - Tk) * 100 / Tb
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fmt.Printf("th = %3d Tk = %10s %4d%%", th, Tk, delta)
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// determine break-even point
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if Tk < Tb && th1 < 0 {
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th1 = th
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fmt.Print(" break-even point")
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}
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// determine diminishing return
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if 0 < delta && delta < deltaOld && th2 < 0 {
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th2 = th
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fmt.Print(" diminishing return")
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}
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deltaOld = delta
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fmt.Println()
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// trigger counter
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if th1 >= 0 && th2 >= 0 && count < 0 {
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count = 10 // this many extra measurements after we got both thresholds
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}
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th++
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}
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}
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func TestCalibrate(t *testing.T) {
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if *calibrate {
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computeThresholds()
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}
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}
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