Ok,
i'm not right,pow in C is :
float powf(float x, float y);
long double powl(long double
use float32 pow for proper comparison or use powl for C double wersion.
This is demonstartion how when you use go long time, you lose ability to
read other languages :)
On Friday, August 4, 2017 at 10:15:06 AM UTC+3, dja...@gmail.com wrote:
>
> You are comparing apples to oranges( integer vs float64 pow),
> use integer pow and compare again:
>
>
> func Pow(a, b int) int {
> p := 1
> for b > 0 {
> if b&1 != 0 {
> p *= a
> }
> b >>= 1
> a *= a
> }
> return p
> }
>
>
> On Friday, August 4, 2017 at 9:20:41 AM UTC+3, Dorival Pedroso wrote:
>>
>> I've noticed that this C code:
>>
>> #include "math.h"
>> int main() {
>> double x = 2.5;
>> int Nmax = 10000000;
>> for (int N=0; N<Nmax; N++) {
>> for (int i=0; i<20; i++) {
>> pow(x, i);
>> }
>> }
>> }
>>
>> can run up to 50x faster than this Go code:
>>
>> package main
>>
>> import "math"
>>
>> func main() {
>> x := 2.5
>> Nmax := 10000000
>> for N := 0; N < Nmax; N++ {
>> for i := 0; i < 20; i++ {
>> math.Pow(x, float64(i))
>> }
>> }
>> }
>>
>> The C code was compiled with: gcc -O2 ccode.c -o ccode -lm
>> then run with time ./ccode
>>
>> The Go code was compiled with: go build gcode.go
>> then run with time ./gcode
>>
>> I've used the time command on Linux (Ubuntu) to get some estimate.
>>
>> So the question is: how can we make the Go code faster?
>>
>
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