$ benchstat old.txt new.txt
name old time/op new time/op delta
Lookup-4 22.9ns ± 8% 21.7ns ± 6% -5.30% (p=0.000 n=20+20)
name old alloc/op new alloc/op delta
Lookup-4 0.00B ±NaN% 0.00B ±NaN% ~ (all samples are equal)
name old allocs/op new allocs/op delta
Lookup-4 0.00 ±NaN% 0.00 ±NaN% ~ (all samples are equal)
Created
February 19, 2018 09:18
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Impetus for switching from generation of [256]uint8 to [256]int for math/bits Len*
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| package main | |
| import "testing" | |
| var len8tab = [256]uint8{ | |
| 0x00, 0x01, 0x02, 0x02, 0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, | |
| 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, | |
| 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, | |
| 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, | |
| 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, | |
| 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, | |
| 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, | |
| 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| } | |
| var len8tabInt = [256]int{ | |
| 0x00, 0x01, 0x02, 0x02, 0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, | |
| 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, | |
| 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, | |
| 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, | |
| 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, | |
| 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, | |
| 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, | |
| 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, | |
| } | |
| var queries = []uint64{ | |
| 0, 1, 1 << 10, 1 << 20, 1 << 30, 17, 1 << 40, 1 << 50, 1 << 60, 1<<64 - 1, | |
| } | |
| func BenchmarkPlainLookup(b *testing.B) { | |
| for i := 0; i < b.N; i++ { | |
| for _, q := range queries { | |
| if v := len64Int(q); v <= 0 { | |
| } | |
| } | |
| } | |
| b.ReportAllocs() | |
| } | |
| func BenchmarkIntCastLookup(b *testing.B) { | |
| for i := 0; i < b.N; i++ { | |
| for _, q := range queries { | |
| if v := len64Cast(q); v <= 0 { | |
| } | |
| } | |
| } | |
| b.ReportAllocs() | |
| } | |
| func len64Cast(x uint64) (n int) { | |
| if x >= 1<<32 { | |
| x >>= 32 | |
| n = 32 | |
| } | |
| if x >= 1<<16 { | |
| x >>= 16 | |
| n += 16 | |
| } | |
| if x >= 1<<8 { | |
| x >>= 8 | |
| n += 8 | |
| } | |
| return n + int(len8tab[x]) | |
| } | |
| func len64Int(x uint64) (n int) { | |
| if x >= 1<<32 { | |
| x >>= 32 | |
| n = 32 | |
| } | |
| if x >= 1<<16 { | |
| x >>= 16 | |
| n += 16 | |
| } | |
| if x >= 1<<8 { | |
| x >>= 8 | |
| n += 8 | |
| } | |
| return n + len8tabInt[x] | |
| } |
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| BenchmarkLookup-4 100000000 22.4 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.1 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.4 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.8 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.4 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.1 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.3 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.9 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 20.8 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.2 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.6 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.4 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 20.8 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 20.4 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 20.5 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.1 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 50000000 22.0 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.8 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.8 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.4 ns/op 0 B/op 0 allocs/op |
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| BenchmarkLookup-4 100000000 24.3 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.6 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 23.5 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.7 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 23.1 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.3 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 24.3 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 23.2 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 23.6 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.8 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 23.0 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 50000000 24.3 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 50000000 24.7 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.8 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.5 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.8 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.7 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.8 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 22.0 ns/op 0 B/op 0 allocs/op | |
| BenchmarkLookup-4 100000000 21.5 ns/op 0 B/op 0 allocs/op |
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