A strange question for bool

[laomz]

type BoolStruct struct {
	b1 bool
	b2 bool
	b3 bool
	b4 bool
	b5 bool
	b6 bool
	b7 bool
	b8 bool
	b  byte
}

func (bs *BoolStruct) DoSomething() {
	bs.b = DoSomethingForBool(bs.b1, bs.b2, bs.b3, bs.b4, bs.b5, bs.b6, bs.b7, bs.b8)
}

func DoSomethingForBool(b1 bool, b2 bool, b3 bool, b4 bool, b5 bool, b6 bool, b7 bool, b8 bool) byte {
	var b byte
	if b1 {
		//do something
		b++
	}
	if b2 {
		//do something
		b++
	}
	if b3 {
		//do something
		b++
	}
	if b4 {
		//do something
		b++
	}
	if b5 {
		//do something
		b++
	}
	if b6 {
		//do something
		b++
	}
	if b7 {
		//do something
		b++
	}
	if b8 {
		//do something
		b++
	}

	return b
}

var bsFalse = BoolStruct{
	b1: false,
	b2: false,
	b3: false,
	b4: false,
	b5: false,
	b6: false,
	b7: false,
	b8: false,
}

func BenchmarkBSFalse(b *testing.B) {
	for i := 0; i < b.N; i++ {
		bsFalse.DoSomething()
	}
}

var bsTrue = BoolStruct{
	b1: true,
	b2: true,
	b3: true,
	b4: true,
	b5: true,
	b6: true,
	b7: true,
	b8: true,
}

func BenchmarkBSTrue(b *testing.B) {
	for i := 0; i < b.N; i++ {
		bsTrue.DoSomething()
	}
}

BenchmarkBSFalse-6 502713746 7.17 ns/op 0 B/op 0 allocs/op
BenchmarkBSTrue-6 1000000000 2.17 ns/op 0 B/op 0 allocs/op

all false consume more time than all true, why?

[ianlancetaylor]

When you are down to a few nanoseconds per operation, it could be the exact alignment of the code in memory, it could be the CPU's memory caching algorithm, it could be the branch predictor, it could be the phase of the moon. Microbenchmarking is hard.

We don't use the issue tracker to discuss issues like this. Use a forum instead. If you identify a problem in the compiler or assembler or linker, then by all means open an issue with details. But the odds are that this is effectively chance, and not something that can be fixed.

[randall77]

Might be #35881

[laomz]

After a lot of testing, I have determined that it is not a memory alignment or cpu cache problem. And the results of repeated tests are the same, is this not strange?

[davecheney]

I’d be suspicious of that benchmark, I think the compiler is optimising always some or all of the code under test.

[ianlancetaylor]

Please use a forum, as described at https://golang.org/wiki/Questions. Thanks.