Perl, Python, Erlang, C语言运行速度的比较

主要是通过 蒙特卡罗法来计算圆周率。代码如下：
1)  pi.pl:

$time1 = time();
foreach (1..20000000) {
  my($x, $y) = (rand(), rand());
  if(sqrt($x ** 2 + $y ** 2) < 1) {
    $total += 1;
  }
}
$pi = 4.0 * $total / 20000000;
$time2 = time();

print "Pi = " , $pi, " time = ", $time2 - $time1;

Perl脚本运行结果如下，2千万次平均执行时间是27秒左右：

2）pi.py

import random
import datetime
import math

starttime = datetime.datetime.now()
total = 0
for i in xrange(20000000):
    x, y = random.random(), random.random()
    if math.sqrt(x ** 2 + y ** 2) < 1:
        total += 1
pi = 4.0 * total / 20000000
endtime = datetime.datetime.now()
print "pi = ", pi , " time = ", (endtime - starttime).seconds

Python运行结果如下，2千万次平均执行时间是30秒左右：

3) pi.erl

-module(pi).
-export([pi/1]).

pi(N) ->
  pi(N, N, 0).

pi(N, 0, Total) -> 4.0 * Total / N;

pi(N, I, Total) ->
  X = random:uniform(),
  Y = random:uniform(),
  R = math:sqrt(X * X + Y * Y),
  if
    R < 1 -> pi(N, I - 1, Total + 1);
    true  -> pi(N, I - 1, Total)
  end.

Erlang运行如下，2千万次平均执行时间是30秒左右：

4) pi.c

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>

int main() {
  time_t start_time, end_time;
  double elapsed_time;
  double x, y, pi;
  long i , total;
  total = 0;
  srand((unsigned)time(0));
  time(&start_time);
  for(i = 0 ; i < 20000000; i ++ ) {
    x = rand() / (double)(RAND_MAX);
    y = rand() / (double)(RAND_MAX);
    if (sqrt(x * x + y * y) < 1) {
      total += 1;
    }
  }
  pi = 4.0 * total / 20000000;
  time(&end_time);
  elapsed_time = difftime(end_time, start_time);
  printf(" total = %d, pi = %f, time = %f", total ,pi, elapsed_time);
}

C运行如下，
2千万次平均执行时间是3秒左右：

Python, Erlang 速度相当， Perl稍微快一丁点， C语言是它们的10倍。