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Merged
merged 2 commits into from
Jan 4, 2019
Merged

C adding FFT test #571

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5802e2f
adding fftw3 test to fft
Gathros Jan 3, 2019
01e43f8
updating cooley_tukey.md
Gathros Jan 3, 2019
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27 changes: 25 additions & 2 deletions contents/cooley_tukey/code/c/fft.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,23 @@
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <fftw3.h>

void fft(double complex *x, int n) {
double complex y[n];
memset(y, 0, sizeof(y));
fftw_plan p;

p = fftw_plan_dft_1d(n, (fftw_complex*)x, (fftw_complex*)y,
FFTW_FORWARD, FFTW_ESTIMATE);

fftw_execute(p);
fftw_destroy_plan(p);

for (size_t i = 0; i < n; ++i) {
x[i] = y[i] / sqrt((double)n);
}
}

void dft(double complex *X, const size_t N) {
double complex tmp[N];
Expand Down Expand Up @@ -79,8 +96,12 @@ void iterative_cooley_tukey(double complex *X, size_t N) {

void approx(double complex *X, double complex *Y, size_t N) {
for (size_t i = 0; i < N; ++i) {
printf("%f\n", cabs(X[i]) - cabs(Y[i]));
if (cabs(X[i]) - cabs(Y[i]) > 1E-5) {
printf("This is not approximate.\n");
return;
}
}
printf("This is approximate.\n");
}

int main() {
Expand All @@ -92,10 +113,12 @@ int main() {
z[i] = x[i];
}

fft(x, 64);
cooley_tukey(y, 64);
iterative_cooley_tukey(z, 64);

approx(y, z, 64);
approx(x, y, 64);
approx(x, z, 64);

return 0;
}
4 changes: 2 additions & 2 deletions contents/cooley_tukey/cooley_tukey.md
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Expand Up @@ -72,7 +72,7 @@ For some reason, though, putting code to this transformation really helped me fi
{% sample lang="jl" %}
[import:4-13, lang:"julia"](code/julia/fft.jl)
{% sample lang="c" %}
[import:8-19, lang:"c"](code/c/fft.c)
[import:25-35, lang:"c"](code/c/fft.c)
{% sample lang="clj" %}
[import:15-30, lang:"clojure"](code/clojure/fft.clj)
{% sample lang="cpp" %}
Expand Down Expand Up @@ -121,7 +121,7 @@ In the end, the code looks like:
{% sample lang="jl" %}
[import:16-32, lang:"julia"](code/julia/fft.jl)
{% sample lang="c" %}
[import:20-39, lang:"c"](code/c/fft.c)
[import:37-56, lang:"c"](code/c/fft.c)
{% sample lang="clj" %}
[import:31-58, lang:"clojure"](code/clojure/fft.clj)
{% sample lang="cpp" %}
Expand Down