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Re: calculation time
Quote:
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Originally Posted by ashraf_leaf
...calculation time...
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'
There are no standard library functions to do what you are asking. I note from a previous post that your are using dev-cpp (I think).
Here's a way to use a function called "ftime" to do the deed. (Current Linux systems and GNU/cygwin have a better function named "gettimeofday" that is preferred, but my dev-cpp doesn't have it. My dev-cpp does have ftime.)
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/timeb.h> /*<--- for ftime */
#define twopi 3.1415926535 * 2.0
struct cpx {
float real;
float imag;
};
typedef struct cpx COMPLEX;
void cExp(COMPLEX z1, COMPLEX * res);
void csum(COMPLEX z1, COMPLEX z2, COMPLEX * res);
void cmult(COMPLEX z1, COMPLEX z2, COMPLEX * res);
void cmplx(float rp, float ip, COMPLEX * z);
void cdif(COMPLEX z1, COMPLEX z2, COMPLEX * res);
void cdiv(COMPLEX z1, COMPLEX z2, COMPLEX * res);
float cnorm(COMPLEX z);
void slowft(float *x, COMPLEX * y, int n);
void evenodd(COMPLEX * x, COMPLEX * y, int n);
static float data[2050];
static COMPLEX Data[2050];
void NEXT()
{
static int i = 0;
static char xc[5] = { '|', '/', '-', '\\', ' ' };
fprintf(stdout, "%c%c", 010, xc[i++]);
fflush(stdout);
if (i > 3)
i = 0;
}
int main()
{
struct timeb tempo1, tempo2;
time_t elapsed_time; /* elapsed time in seconds */
int elapsed_mtime; /* elapsed time in milliseconds */
time_t elapsed_seconds; /* diff between seconds counter */
time_t elapsed_mseconds; /* diff between milliseconds counter */
int i, j, k, n;
double x, y, z, t, t2;
FILE *f;
int nn, num_transforms = 1000;
n = 1024; /* Size of sampled signal */
t = 1.0 / 128.0; /* Period of signal */
t2 = 1.0 / 300.0;
ftime(&tempo1); /* starting time */
for (nn = 0; nn < num_transforms; nn++) {
for (i = 0; i < n; i++) {
data[i] = 2.0 * sin(twopi * t * i)
/* + 3*sin (twopi * t2 * i) */ ;
data[i + n] = 0.0;
}
}
ftime(&tempo2); /* ending time */
printf("tempo2.time = %ld, tempo2.millitm = %ld\n",
tempo2.time, tempo2.millitm);
printf("tempo1.time = %ld, tempo1.millitm = %ld\n",
tempo1.time, tempo1.millitm);
elapsed_seconds = tempo2.time - tempo1.time;
elapsed_mseconds = tempo2.millitm - tempo1.millitm;
printf("Elapsed time = %ld seconds + %ld milliseconds\n",
elapsed_seconds, elapsed_mseconds);
elapsed_mtime = (elapsed_seconds) *1000 + elapsed_mseconds;
printf("Elapsed time for %d transforms = %ld milliseconds\n",
num_transforms, elapsed_mtime);
printf("Fourier Transform of sine wave: vers. 4\n");
slowft(data, Data, 1024);
f = fopen("slow4.out", "w");
if (f == NULL) {
printf("Can't open the output file 'slow4.out'\n");
exit(1);
}
for (i = 0; i < n; i++)
fprintf(f, "%d %f\n", i, cnorm(Data[i]));
fclose(f);
return (0);
data[0] = -6.0;
data[1] = -2.0;
data[2] = 0.0;
data[3] = 2.0;
data[4] = 4.0;
data[5] = 6.0;
data[6] = 3.0;
data[7] = -1.0;
slowft(data, Data, 8);
printf(" M Real imag\n");
for (i = 0; i <= 4; i++)
printf(" %2d %8.4f %8.4f\n", i, Data[i].real, Data[i].imag);
exit(0);
}
void cExp(COMPLEX z1, COMPLEX * res)
{
COMPLEX x, y;
x.real = exp((double) z1.real);
x.imag = 0.0;
y.real = (float) cos((double) z1.imag);
y.imag = (float) sin((double) z1.imag);
cmult(x, y, res);
}
void cmult(COMPLEX z1, COMPLEX z2, COMPLEX * res)
{
res->real = z1.real * z2.real - z1.imag * z2.imag;
res->imag = z1.real * z2.imag + z1.imag * z2.real;
}
void csum(COMPLEX z1, COMPLEX z2, COMPLEX * res)
{
res->real = z1.real + z2.real;
res->imag = z1.imag + z2.imag;
}
void cdif(COMPLEX z1, COMPLEX z2, COMPLEX * res)
{
res->real = z1.real - z2.real;
res->imag = z1.imag - z2.imag;
}
void cdiv(COMPLEX z1, COMPLEX z2, COMPLEX * res)
{
float z, real, imag;
z = cnorm(z2);
if (z != 0.0) {
res->real = (z1.real * z2.real + z1.imag * z2.imag) / z;
res->imag = (z2.real * z1.imag - z1.real * z2.imag) / z;
return;
}
res->real = res->imag = 0.0;
printf("ZERO DIVIDE!\n");
}
void cmplx(float rp, float ip, COMPLEX * z)
{
z->real = rp;
z->imag = ip;
}
float cnorm(COMPLEX z)
{
return z.real * z.real + z.imag * z.imag;
}
void slowft(float *x, COMPLEX * y, int n)
{
COMPLEX *xx;
int i;
xx = (COMPLEX *) malloc(sizeof(struct cpx) * 1024);
for (i = 0; i < n; i++)
cmplx(x[i], 0.0, &(xx[i]));
evenodd(xx, y, n);
free(xx);
}
void evenodd(COMPLEX * x, COMPLEX * y, int n)
{
int m, i;
COMPLEX *Sum, *Diff;
COMPLEX *Even, *Odd;
COMPLEX z1, z2, z3, z4, tmp, two;
float xs, ys;
if (n < 1)
printf("What???? \n");
/* The simple case, where N=1 */
cmplx(2.0, 0.0, &two);
if (n == 1) {
cmplx(x[0].real, x[0].imag, &(y[0]));
return;
}
/* Otherwise, N is even */
m = n / 2;
cmplx(0.0, atan(1.0) / n * -8.0, &z1);
cExp(z1, &tmp);
cmplx(1.0, 0.0, &z1);
/* Allocate temporary space */
Sum = (COMPLEX *) malloc(sizeof(struct cpx) * m);
Diff = (COMPLEX *) malloc(sizeof(struct cpx) * m);
Even = (COMPLEX *) malloc(sizeof(struct cpx) * m);
Odd = (COMPLEX *) malloc(sizeof(struct cpx) * m);
if (Sum == 0 || Diff == 0 || Even == 0 || Odd == 0) {
printf("Panic - not enough memory.\n");
exit(1);
}
for (i = 0; i < m; i++) {
NEXT();
csum(x[i], x[i + m], &z3);
cdiv(z3, two, &(Sum[i]));
cdif(x[i], x[i + m], &z3);
cmult(z3, z1, &z4);
cdiv(z4, two, &(Diff[i]));
cmult(z1, tmp, &z2);
cmplx(z2.real, z2.imag, &z1);
}
evenodd(Sum, Even, m);
evenodd(Diff, Odd, m);
for (i = 0; i < m; i++) {
y[i * 2].real = Even[i].real;
y[i * 2].imag = Even[i].imag;
y[i * 2 + 1].real = Odd[i].real;
y[i * 2 + 1].imag = Odd[i].imag;
}
free(Sum);
free(Diff);
free(Even);
free(Odd);
}
Note that in order to get some meaningful measurements in milliseconds I had to do the transform more than once.
On my very modest Windows XP platform, the results of one run are:
Code:
tempo2.time = 1203984483, tempo2.millitm = 151
tempo1.time = 1203984482, tempo1.millitm = 995
Elapsed time = 1 seconds + -844 milliseconds
Elapsed time for 1000 transforms = 156 milliseconds
Fourier Transform of sine wave: vers. 4
Note that the accuracy of the timing is not guaranteed (depends on what else is using CPU time on your system at the time). It should be OK for comparison purposes if your system is equally busy (or unbusy) for subsequent runs.
Regards,
Dave
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25-Feb-2008, 16:22
, but it works also in mvc++6.
Developing GUIs with wxPython (Part 2) by crystalattice
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