go byte array benchmark

benchmark.go

package main

import (
    "fmt"
    "time"
    "unsafe"
    "math"
    "math/rand"
)

const times = 15000000000

var buf = make([]byte, rand.Intn(10))
var byteHolder byte

func testGetFloat64() time.Duration {
	ts := time.Now()
	var f64 float64
	for i := 0; i < times; i++ {
		// seems got passed boundary check this way, faster than &buf[x]
		// not familiar with golang though...
		pt := uintptr(unsafe.Pointer(&buf)) + unsafe.Sizeof(byteHolder) * 3
		p := (*float64)(unsafe.Pointer(pt))
		f64 = *p
	}
	fmt.Println(f64)

	te := time.Now()
	return te.Sub(ts)
}

func testSetFloat64() time.Duration {
	ts := time.Now()
	var f64 float64
	f64 = 10.7
	for i := 0; i < times; i++ {
		pt := uintptr(unsafe.Pointer(&buf)) + unsafe.Sizeof(byteHolder) * 3
		p := (*float64)(unsafe.Pointer(pt))
		*p = f64
	}
	te := time.Now()
	return te.Sub(ts)
}

func testGetFloat64Datum() time.Duration {
	ts := time.Now()
	var i64 int64
	i64 = 10
	var f64 float64
	for i := 0; i < times; i++ {
		f64 = math.Float64frombits(uint64(i64))
	}
	f64 = f64 + 1.0
	te := time.Now()
	return te.Sub(ts)
}

func testSetFloat64Datum() time.Duration {
	ts := time.Now()
	var kind byte
	var i64 int64

	var f64 float64
	f64 = 10.0
	for i := 0; i < times; i++ {
		kind = 1
		i64 = int64(math.Float64bits(f64))
	}
	kind = kind + 1
	i64 = i64 + 1
	te := time.Now()
	return te.Sub(ts)
}

func testGetInt64Datum() time.Duration {
	var i64 int64
	var val int64 = int64(rand.Intn(88))

	ts := time.Now()
	for i := 0; i < times; i++ {
		i64 = val
	}
	i64 = i64 + 1
	te := time.Now()
	return te.Sub(ts)
}

func testGetInt64() time.Duration {
	ts := time.Now()
	var i64 int64
	for i := 0; i < times; i++ {
		// seems got passed boundary check this way, faster than &buf[x]
		// not familiar with golang though...
		pt := uintptr(unsafe.Pointer(&buf)) + unsafe.Sizeof(byteHolder) * 3
		p := (*int64)(unsafe.Pointer(pt))
		i64 = *p
	}
	i64 = i64 + 1

	te := time.Now()
	return te.Sub(ts)
}

func main() {
	fmt.Println("testSetFloat64: ")
	fmt.Println(testSetFloat64())

	fmt.Println("testGetFloat64: ")
	fmt.Println(testGetFloat64())

	fmt.Println("testSetFloat64Datum: ")
	fmt.Println(testSetFloat64Datum())

	fmt.Println("testGetFloat64Datum: ")
	fmt.Println(testGetFloat64Datum())


	fmt.Println("testGetInt64Datum: ")
	fmt.Println(testGetInt64Datum())

	fmt.Println("testGetInt64: ")
	fmt.Println(testGetInt64())
}

这样子玩unsafe.Pointer容易失控，Go毕竟不是C。
另外，这种对列存的数据库比较合适，而对行存的Row各个column编码并不一样，不容易紧凑的编码。