abs_test.go

package abs

import (
	"math/rand"
	"reflect"
	"runtime"
	"strings"
	"testing"
)

const (
	MaxInt int64 = 1<<63 - 1
	MinInt int64 = -1 << 63
)

// An absFunc is a function that returns the absolute value of an integer.
type absFunc func(int64) int64

var (
	testInputs  = []int64{MinInt + 1, MinInt + 2, -1, -0, 1, 2, MaxInt - 1, MaxInt}
	testOutputs = []int64{MaxInt, MaxInt - 1, 1, 0, 1, 2, MaxInt - 1, MaxInt}
	testFuncs   = []absFunc{
		WithBranch,
		WithStdLib, // test failure expected on large numbers
		WithTwosComplement,
		WithASM,
	}
)

func funcName(v interface{}) string {
	s := runtime.FuncForPC(reflect.ValueOf(v).Pointer()).Name()
	return s[strings.LastIndex(s, ".")+1:]
}

// func TestAbs(t *testing.T) {
// 	for _, f := range testFuncs {
// 		testName := funcName(f)
// 		t.Run(testName, func(t *testing.T) {
// 			for i := 0; i < len(testInputs); i++ {
// 				actual := f(testInputs[i])
// 				if actual != testOutputs[i] {
// 					t.Errorf("%s(%d)", testName, testInputs[i])
// 					t.Errorf("	input:		%064b (%d)", uint64(testInputs[i]), testInputs[i])
// 					t.Errorf("	expected:	%064b (%d)", uint64(testOutputs[i]), testOutputs[i])
// 					t.Errorf("	actual:		%064b (%d)", uint64(actual), actual)
// 				}
// 			}
// 		})
// 	}
// }

func randData(n int) []int64 {
	data := make([]int64, n)
	for i := range data {
		data[i] = rand.Int63() << 1
	}
	return data
}

func BenchmarkWithBranch(b *testing.B) {
	data := randData(1 << 16)
	b.ResetTimer()
	for n := 0; n < b.N; n++ {
		for _, x := range data {
			WithBranch(x)
		}
	}
}
func BenchmarkWithStdLib(b *testing.B) {
	data := randData(1 << 16)
	b.ResetTimer()
	for n := 0; n < b.N; n++ {
		for _, x := range data {
			WithStdLib(x)
		}
	}
}

func BenchmarkWithTwosComplement(b *testing.B) {
	data := randData(1 << 16)
	b.ResetTimer()
	for n := 0; n < b.N; n++ {
		for _, x := range data {
			WithTwosComplement(x)
		}
	}
}

func BenchmarkWithASM(b *testing.B) {
	data := randData(1 << 16)
	b.ResetTimer()
	for n := 0; n < b.N; n++ {
		for _, x := range data {
			WithASM(x)
		}
	}
}