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/* ####################################################################### */
/* This script compares the speed of the computation of a polynomial */
/* in C in a couple of different ways. */
/* */
/* Author: Francesc Alted */
/* Date: 2010-02-05 */
/* ####################################################################### */
#include <stdio.h>
#include <math.h>
#if defined(_WIN32) && !defined(__MINGW32__)
#include <time.h>
#include <windows.h>
#else
#include <unistd.h>
#include <sys/time.h>
#endif
#define N 10*1000*1000
double x[N];
double y[N];
#if defined(_WIN32) && !defined(__MINGW32__)
#if defined(_MSC_VER) || defined(_MSC_EXTENSIONS)
#define DELTA_EPOCH_IN_MICROSECS 11644473600000000Ui64
#else
#define DELTA_EPOCH_IN_MICROSECS 11644473600000000ULL
#endif
struct timezone
{
int tz_minuteswest; /* minutes W of Greenwich */
int tz_dsttime; /* type of dst correction */
};
int gettimeofday(struct timeval *tv, struct timezone *tz)
{
FILETIME ft;
unsigned __int64 tmpres = 0;
static int tzflag;
if (NULL != tv)
{
GetSystemTimeAsFileTime(&ft);
tmpres |= ft.dwHighDateTime;
tmpres <<= 32;
tmpres |= ft.dwLowDateTime;
/*converting file time to unix epoch*/
tmpres -= DELTA_EPOCH_IN_MICROSECS;
tmpres /= 10; /*convert into microseconds*/
tv->tv_sec = (long)(tmpres / 1000000UL);
tv->tv_usec = (long)(tmpres % 1000000UL);
}
if (NULL != tz)
{
if (!tzflag)
{
_tzset();
tzflag++;
}
tz->tz_minuteswest = _timezone / 60;
tz->tz_dsttime = _daylight;
}
return 0;
}
#endif /* _WIN32 */
/* Given two timeval stamps, return the difference in seconds */
float getseconds(struct timeval last, struct timeval current) {
int sec, usec;
sec = current.tv_sec - last.tv_sec;
usec = current.tv_usec - last.tv_usec;
return (float)(((double)sec + usec*1e-6));
}
int main(void) {
int i;
double inf = -1;
struct timeval last, current;
float tspend;
for(i=0; i<N; i++) {
x[i] = inf+(2.*i)/N;
}
gettimeofday(&last, NULL);
for(i=0; i<N; i++) {
//y[i] = .25*pow(x[i],3.) + .75*pow(x[i],2.) - 1.5*x[i] - 2;
y[i] = ((.25*x[i] + .75)*x[i] - 1.5)*x[i] - 2;
}
gettimeofday(¤t, NULL);
tspend = getseconds(last, current);
printf("Compute time:\t %.3fs\n", tspend);
}
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