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| #include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <complex.h>
void FFT(double complex *,double complex *,int );
void FFT(double complex *l,double complex *r,int p)
{
int N = pow( (double)2 , (double)p );
double complex *w = malloc( N * sizeof *w );
w[0] = 1 + 0 * I;
/*mise en place de la liste des puissances de w*/
double complex c= cos( 2. * M_PI / N ) - sin( 2. * M_PI / N ) * I;
for(int i1 = 0 ; i1 <= N-2 ; i1++ )
w[i1+1] = w[i1] * c;
/*inversions des bits*/
int w1, z, s, d;
for( int k = 0 ; k <= N-1 ; k++ )
{
w1 = 0;
z = k;
s = 0;
d = N/2;
for( int k1 = 0; k1 <= p-1 ; k1++ )
{
if ( z == 0 )
break;
if(z!=0)
{
w1 = z % 2;
s += w1 * d;
d /= 2;
}
z = (z-w1) / 2;
}
r[k] = l[s];
}
/*la partie calcul proprement dite*/
{
int d1 = N/2;
int d2 = 1;
for (int j = 1; j <= p; j++)
{
for(int i = 0; i <= d1-1; i++)
{
for(int b = 0; b <= d2-1; b++)
{
double complex r1inter = r[ i * 2 * d2 + b ];
double complex r2inter = r[ i * 2 * d2 + b + d2 ];
r[ i * 2 * d2 + b ] = ( r1inter + r2inter * w[b] ) * 0.5;
r[ i * 2 * d2 + b + d2 ] = ( r1inter - r2inter * w[b] ) * 0.5;
}
}
d1 /= 2;
d2 *= 2;
}
}
free(w);
}
int main(void)
{
double complex *testprime = malloc( 8 * sizeof *testprime );
double complex *result1prime = malloc( 8 * sizeof *result1prime );
testprime[0]=40.;
testprime[1]=23.;
testprime[2]=1.;
testprime[3]=54.;
testprime[4]=1.;
testprime[5]=8.;
testprime[6]=1.;
testprime[7]=4.;
FFT( testprime, result1prime, 3);
for( int lambda = 0; lambda <= 7; lambda++)
(void) printf("%lg + %lg*i \n", creal( result1prime[lambda] ), cimag( result1prime[lambda] ));
free(testprime);
free(result1prime);
return EXIT_SUCCESS;
} |
Algo FFT problème!
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Envoyé par e_gaillard37
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