C++編譯器性能比較

現在市面上，主流的C/C++編譯器包括M$的CL、gcc、Intel的icl、PGI的pgcc及Codegear的bcc（原來屬於Borland公司）。Windows上使用最多的自然是cl，而在更廣闊的平台上，gcc則是C/C++編譯器的首選。但要提到能力優化，排名就未必與它們的市場占有率一致了。

今天一時興起，便做了一個各編譯器數值性能的比較。測試的代碼是一個求積分的程序，來源於intel編譯器的例子程序，修改了一個頭文件，以便每個編譯器都能編譯。

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

// Function to be integrated
// Define and prototype it here
// | sin(x) |
#define INTEG_FUNC(x) fabs(sin(x))

// Prototype timing function
double dclock(void);

int main(void)
{
// Loop counters and number of interior points
unsigned int i, j, N;
// Stepsize, independent variable x, and accumulated sum
double step, x_i, sum;
// Timing variables for evaluation
double start, finish, duration, clock_t;
// Start integral from
double interval_begin = 0.0;
// Complete integral at
double interval_end = 2.0 * 3.141592653589793238;

// Start timing for the entire application
start = clock();

printf(" \n");
printf(" Number of | Computed Integral | \n");
printf(" Interior Points | | \n");
for (j=2;j<27;j++)
{
printf("------------------------------------- \n");

// Compute the number of (internal rectangles + 1)
N = 1 << j;

// Compute stepsize for N-1 internal rectangles
step = (interval_end - interval_begin) / N;

// Approx. 1/2 area in first rectangle: f(x0) * [step/2]
sum = INTEG_FUNC(interval_begin) * step / 2.0;

// Apply midpoint rule:
// Given length = f(x), compute the area of the
// rectangle of width step
// Sum areas of internal rectangle: f(xi + step) * step

for (i=1;i<N;i++)
{
x_i = i * step;
sum += INTEG_FUNC(x_i) * step;
}

// Approx. 1/2 area in last rectangle: f(xN) * [step/2]
sum += INTEG_FUNC(interval_end) * step / 2.0;

printf(" %10d | %14e | \n", N, sum);
}
finish = clock();
duration = (finish - start);
printf(" \n");
printf(" Application Clocks = %10e \n", duration);
printf(" \n");

return 0;
}