filter_test.go

filter-my-ass

func FilterJunior(s []int) []int {
	var pos = 0
	for i := 0; i < len(s); i++ {
		if s[i]%3 != 0 {
			s[pos] = s[i]
			pos++
		}
	}
	return s[:pos]
}

func FilterBob(s []int) []int {
	res := s[:0]
	for i := range s {
		if s[i]%3 != 0 {
			res = append(res, s[i])
		}
	}
	return res
}

func FilterPates(s []int) []int {
	for i := 0; i < len(s); i++ {
		if s[i]%3 == 0 {
			s = append(s[:i], s[i+1:]...)
		}
	}
	return s
}

func BenchmarkFilter(b *testing.B) {
	in := make([]int, 10000)
	for i := range in {
		in[i] = rand.Int()
	}
	b.Run("filter-junior", func(b *testing.B) {
		b.ReportAllocs()
		for i := 0; i < b.N; i++ {
			FilterJunior(in)
		}
	})

	b.Run("filter-bob", func(b *testing.B) {
		b.ReportAllocs()
		for i := 0; i < b.N; i++ {
			FilterBob(in)
		}
	})

	b.Run("filter-pates", func(b *testing.B) {
		b.ReportAllocs()
		for i := 0; i < b.N; i++ {
			FilterPates(in)
		}
	})
}
// goos: darwin
// goarch: amd64
// pkg: workerpool
// BenchmarkFilter/filter-junior-12         	  100000	     13468 ns/op	       0 B/op	       0 allocs/op
// BenchmarkFilter/filter-bob-12            	  100000	     14033 ns/op	       0 B/op	       0 allocs/op
// BenchmarkFilter/filter-pates-12          	  200000	     10222 ns/op	       0 B/op	       0 allocs/op
// PASS


func TestFilter(t *testing.T) {
	require.Equal(t, []int{}, FilterJunior([]int{}))
	require.Equal(t, []int{1}, FilterJunior([]int{1}))
	require.Equal(t, []int{1, 2}, FilterJunior([]int{1, 2, 3}))
	require.Equal(t, []int{1, 2}, FilterJunior([]int{9, 1, 2, 3}))
	require.Equal(t, []int{1, 2}, FilterJunior([]int{9, 1, 27, 2, 3}))
	require.Equal(t, []int{}, FilterJunior([]int{3}))

	require.Equal(t, []int{}, FilterBob([]int{}))
	require.Equal(t, []int{1}, FilterBob([]int{1}))
	require.Equal(t, []int{1, 2}, FilterBob([]int{1, 2, 3}))
	require.Equal(t, []int{1, 2}, FilterBob([]int{9, 1, 2, 3}))
	require.Equal(t, []int{1, 2}, FilterBob([]int{9, 1, 27, 2, 3}))
	require.Equal(t, []int{}, FilterBob([]int{3}))

	require.Equal(t, []int{}, FilterPates([]int{}))
	require.Equal(t, []int{1}, FilterPates([]int{1}))
	require.Equal(t, []int{1, 2}, FilterPates([]int{1, 2, 3}))
	require.Equal(t, []int{1, 2}, FilterPates([]int{9, 1, 2, 3}))
	require.Equal(t, []int{1, 2}, FilterPates([]int{9, 1, 27, 2, 3}))
	require.Equal(t, []int{}, FilterPates([]int{3}))
}