src.go

func longFunc(x float64) float64 {
	var sum float64 = 0

	for i := float64(0); i < x; i++ {
		sum = math.Sin(i)
	}

	return sum
}

func benchmarkFold(f fold, b *testing.B) {
	var s = make(slice, 100)

	for i := range s {
		s[i] = 100 * float64(i)
	}

	for n := 0; n < b.N; n++ {
		f(s, longFunc)
	}
}

tests.sh

$ go test -bench . -benchtime 1s
PASS
BenchmarkFoldFast-4          300           4928328 ns/op
BenchmarkFoldParallel-4      300           4870866 ns/op
BenchmarkFoldSimple-4        100          18261889 ns/op
ok      github.com/the-varlog/fold      5.775s