求圆周率（Go语言实现）

求圆周率（Go语言实现）

 

圆周率算法来源于莱布尼茨公式，效率很低并且精度也不够，以下是运行结果：

[ `go run demo.go` | done: 5m12.5903356s ]（即一共运行了5分12秒）[3 1 4 1 5 9 2 5 5 3 5 8 9 7 9 3 2 3 8 4 6 2 8 9 3 3 8 3 2 7 9 5 0 2 8 8 1 0 7 2 1 6 9 3 9 9 3 7 5 2 0 1 1 3 3 4 7 4 9 4 4 5 8 6 8 9 7 6 6 0 1 5 6 2 8 6 7 0 2 3 6 7 7 6 8 6 5 9 7 5 9 3 5 6 6 4 3 4 3 5 1 8 1 8 1 6 1 1 5 1 3 8 7 6 7 6 2 8 9 8 7 1 5 9 6 1 0 9 0 7 7 9 8 7 4 9 4 3 7 5 6 4 1 6 2 5 1 9 9 3 2 1 5 4 2 6 2 9 2 1 8 4 0 5 2 5 6 8 5 7 3 8 9 1 1 1 8 8 9 3 6 8 6 4 4 9 7 9 5 6 7 2 2 0 6 0 1 8 3 0 8 4 0 6 9 0 6 6 8 7 5 2 6 0 9 6 5 5 2 6 6 4 6 0 4 3 0 9 0 6 8 7 1 1 9 1 8 5 0 8 0 3 2 3 7 1 1 5 4 2 9 7 4 4 4 9 1 0 2 9 6 8 4 4 9 5 9 4 0 4 7 0 6 6 6 7 2 4 7 3 4 0 7 3 9 0 7 6 4 3 8 3 7 4 4 4 6 8 0 7 6 2 6 5 7 6 0 1 4 5 2 3 8 7 5 3 6 5 5 6 9 8 9 1 6 4 2 6 9 8 6 8 4 0 7 7 4 0 9 2 5 9 9 6 4 3 6 2 5 7 6 1 1 3 0 7 9 8 6 9 6 0 9 4 6 4 1 6 1 7 2 1 7 2 6 5 4 0 2 2 2 6 0 7 6 8 2 4 4 9 4 6 6 0 8 1 5 2 4 1 2 0 3 2 9 6 8 6 0 8 5 0 4 7 8 9 0 7 3 6 3 0 7 1 4 7 7 0 9 4 7 4 7 2 2 2 2 7 2 1 7 5 2 3 4 7 8 8 6 9 3 2 6 8 0 9 1 4 3 5 3 8 9 4 3 2 8 7 8 5 4 5 6 9 4 4 1 6 4 2 7 3 5 8 4 7 1 9 6 7 6 1 2 1 6 8 1 6 6 0 0 4 8 2 6 2 0 5 4 5 3 1 4 5 7 5 1 1 4 3 7 6 7 3 0 5 7 4 0 3 5 3 7 7 6 4 4 5 1 8 0 3 6 9 8 9 7 8 3 2 5 4 1 6 4 5 2 0 2 6 6 3 0 9 3 2 1 6 4 1 0 4 6 0 0 8 2 4 8 7 0 9 0 0 9 0 2 1 5 6 8 7 0 3 5 8 8 1 4 6 7 6 6 9 1 9 7 4 6 4 5 6 0 2 3 5 5 0 6 2 4 9 4 4 2 6 4 6 6 3 4 7 9 8 5 1 6 9 0 3 0 0 8 1 5 8 3 6 5 1 3 2 9 3 8 2 8 1 0 8 7 9 2 2 1 3 6 4 0 8 1 6 0 5 5 7 2 6 0 6 3 9 4 3 5 1 3 2 2 8 6 0 9 8 5 6 7 9 6 8 4 5 9 0 8 3 5 0 3 9 7 1 3 9 8 4 8 7 9 2 4 7 2 9 7 8 2 1 6 6 1 5 6 7 2 8 8 1 3 9 1 2 6 7 0 0 0 3 7 0 5 1 9 2 6 6 8 3 6 1 9 0 3 4 0 4 0 7 3 2 8 9 5 2 2 1 3 8 9 8 7 7 0 5 1 0 1 1 2 8 5 1 8 8 6 3 9 7 8 2 1 7 3 8 7 3 2 9 4 7 5 3 6 8 1 1 0 1 8 4 8 4 8 9 2 8 5 1 3 3 5 4 0 6 4 0 9 7 3 0 2 4 4 4 2 4 2 0 4 0 1 7 2 8 4 8 4 0 9 6 6 0 0 7 5 9 7 7 0 8 1 1 1 5 1 6 5 9 0 1 4 3 3 9 7 8 9 0 2 3 3 8 2 6 3 3 1 8 2 5 9 5 2 6 0 8 0 3 2 6 5 1 5 5 8 8 6 3 8 7 2 2 4 9 8 2 7 5 8 2 3 7 2 8 3 0 7 1 7 1 1 7 6 7 1 6 8 4 1 2 6 2 2 4 4 3 1 3 8 8 3 5 1 5 5 1 2 8 6 5 2 8 8 9 8 5 2 3 0 2 6 3 6 7 8 0 3 1 1 6 3 9 9 6 5 0 9 6 5 2]

Go语言实现代码：

package mainimport ("fmt")type myInt int32const (SIZE    = 120      //数组长度  数据长度小于：120*9TIMES   = 10000000 //迭代次数PRESIZE = 1000     //数字的有效位数)/**代码作者：天之*博客：http://blog.csdn.net/WAPWO?viewmode=contents */func main() {res, bRes := make([]byte, PRESIZE), make([]byte, PRESIZE)rab(res, bRes)int4Res(res)fmt.Println("\n", res)}/*  圆周率 4*[1-1/3+1/5-1/7+...]  */func rab(res, bRes []byte) {intDiv(2, 3, res)var x myInt = 5for i := 2; i < TIMES; i++ {intDiv(1, x, bRes)if i&1 == 0 {intSum(res, bRes)} else {intDif(res, bRes)}x += 2}}/*四倍的sum*/func int4Res(res []byte) {tmp := make([]byte, PRESIZE)cpyByteArr(tmp, res)intSum(res, tmp)intSum(res, tmp)intSum(res, tmp)}/*求和值  res=res-bRes  （因为已知是不会溢出的） */func intSum(res, bRes []byte) {var count bytefor i := PRESIZE - 1; i >= 0; i-- {count = res[i] + bRes[i]if count >= 10 {res[i-1] += 1res[i] = count - 10} else {res[i] = count}}}/*求差值  res=res-bRes  （因为已知是不会溢出的） */func intDif(res, bRes []byte) {var j intfor i := PRESIZE - 1; i >= 0; i-- {if res[i] < bRes[i] {for j = i - 1; res[j] == 0; j-- {res[j] = 9}res[j] -= 1res[i] = res[i] - bRes[i] + 10} else {res[i] = res[i] - bRes[i]}}}/*求除数  res=a/b  */func intDiv(a, b myInt, res []byte) {var count bytefor i := 0; i < PRESIZE; i++ {count = (byte)(a / b)if count == 0 {a *= 10res[i] = 0} else {a %= ba *= 10res[i] = count}}}/*复制整型数组*/func cpyByteArr(d, s []byte) {for i := 0; i < PRESIZE; i++ {d[i] = s[i]}}