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Merge pull request #104968 from twpayne/twpayne/ones-count-64

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Speed up counting of bits in allocator
This commit is contained in:
Kubernetes Prow Robot 2021-10-01 19:27:05 -07:00 committed by GitHub
commit 0ac956ff2b
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2 changed files with 18 additions and 2 deletions
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4
pkg/registry/core/service/allocator/utils.go
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@ -24,8 +24,8 @@ import (
// countBits returns the number of set bits in n
func countBits(n *big.Int) int {
var count int = 0
for _, b := range n.Bytes() {
count += bits.OnesCount8(uint8(b))
for _, w := range n.Bits() {
count += bits.OnesCount64(uint64(w))
}
return count
}

16
pkg/registry/core/service/allocator/utils_test.go
View File

@ -22,12 +22,18 @@ import (
)
func TestCountBits(t *testing.T) {
// bigN is an integer that occupies more than one big.Word.
bigN, ok := big.NewInt(0).SetString("10000000000000000000000000000000000000000000000000000000000000000", 16)
if !ok {
t.Fatal("Failed to set bigN")
}
tests := []struct {
n *big.Int
expected int
}{
{n: big.NewInt(int64(0)), expected: 0},
{n: big.NewInt(int64(0xffffffffff)), expected: 40},
{n: bigN, expected: 1},
}
for _, test := range tests {
actual := countBits(test.n)
@ -36,3 +42,13 @@ func TestCountBits(t *testing.T) {
}
}
}
func BenchmarkCountBits(b *testing.B) {
bigN, ok := big.NewInt(0).SetString("10000000000000000000000000000000000000000000000000000000000000000", 16)
if !ok {
b.Fatal("Failed to set bigN")
}
for i := 0; i < b.N; i++ {
countBits(bigN)
}
}