mirror of
https://github.com/golang/go
synced 2024-11-18 14:34:39 -07:00
b7f0150d16
This function accounts for 2% of "godoc -analysis=pointer" and this change makes it twice as fast---and simpler. Added test and benchmark. Change-Id: I8578fa42dce34df057d81f6c522a7b4e0506d09d Reviewed-on: https://go-review.googlesource.com/15211 Run-TryBot: Robert Griesemer <gri@golang.org> Reviewed-by: Ilya Tocar <ilya.tocar@intel.com> Reviewed-by: Robert Griesemer <gri@golang.org>
59 lines
1.2 KiB
Go
59 lines
1.2 KiB
Go
// Copyright 2014 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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package intsets
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import (
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"math/rand"
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"testing"
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)
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func TestNLZ(t *testing.T) {
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// Test the platform-specific edge case.
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// NB: v must be a var (not const) so that the word() conversion is dynamic.
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// Otherwise the compiler will report an error.
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v := uint64(0x0000801000000000)
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n := nlz(word(v))
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want := 32 // (on 32-bit)
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if bitsPerWord == 64 {
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want = 16
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}
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if n != want {
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t.Errorf("%d-bit nlz(%d) = %d, want %d", bitsPerWord, v, n, want)
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}
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}
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// Backdoor for testing.
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func (s *Sparse) Check() error { return s.check() }
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func dumbPopcount(x word) int {
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var popcnt int
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for i := uint(0); i < bitsPerWord; i++ {
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if x&(1<<i) != 0 {
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popcnt++
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}
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}
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return popcnt
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}
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func TestPopcount(t *testing.T) {
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for i := 0; i < 1e5; i++ {
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x := word(rand.Uint32())
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if bitsPerWord == 64 {
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x = x | (word(rand.Uint32()) << 32)
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}
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want := dumbPopcount(x)
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got := popcount(x)
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if got != want {
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t.Errorf("popcount(%d) = %d, want %d", x, got, want)
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}
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}
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}
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func BenchmarkPopcount(b *testing.B) {
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for i := 0; i < b.N; i++ {
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popcount(word(i))
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}
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}
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