mirror of
https://github.com/golang/go
synced 2024-09-30 22:58:34 -06:00
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.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package intsets
|
|
|
|
import (
|
|
"math/rand"
|
|
"testing"
|
|
)
|
|
|
|
func TestNLZ(t *testing.T) {
|
|
// Test the platform-specific edge case.
|
|
// NB: v must be a var (not const) so that the word() conversion is dynamic.
|
|
// Otherwise the compiler will report an error.
|
|
v := uint64(0x0000801000000000)
|
|
n := nlz(word(v))
|
|
want := 32 // (on 32-bit)
|
|
if bitsPerWord == 64 {
|
|
want = 16
|
|
}
|
|
if n != want {
|
|
t.Errorf("%d-bit nlz(%d) = %d, want %d", bitsPerWord, v, n, want)
|
|
}
|
|
}
|
|
|
|
// Backdoor for testing.
|
|
func (s *Sparse) Check() error { return s.check() }
|
|
|
|
func dumbPopcount(x word) int {
|
|
var popcnt int
|
|
for i := uint(0); i < bitsPerWord; i++ {
|
|
if x&(1<<i) != 0 {
|
|
popcnt++
|
|
}
|
|
}
|
|
return popcnt
|
|
}
|
|
|
|
func TestPopcount(t *testing.T) {
|
|
for i := 0; i < 1e5; i++ {
|
|
x := word(rand.Uint32())
|
|
if bitsPerWord == 64 {
|
|
x = x | (word(rand.Uint32()) << 32)
|
|
}
|
|
want := dumbPopcount(x)
|
|
got := popcount(x)
|
|
if got != want {
|
|
t.Errorf("popcount(%d) = %d, want %d", x, got, want)
|
|
}
|
|
}
|
|
}
|
|
|
|
func BenchmarkPopcount(b *testing.B) {
|
|
for i := 0; i < b.N; i++ {
|
|
popcount(word(i))
|
|
}
|
|
}
|