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Finalisation de l'algorithme de calcul de la FFT

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This commit is contained in:
Guillaume Courrier 2019-11-26 18:01:16 +01:00
parent 37fcd07631
commit de10839794
2 changed files with 56 additions and 16 deletions
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41
tests/examples/test-fft.cpp
View file

@ -1,13 +1,50 @@
#include <math.hpp>
#include <cmath>
#include <fstream>
#include <ctime>
void create_plot_file(std::string filename, const math::csignal& tfd) {
std::ofstream data_file(filename + ".data");
for (int i=0; i<tfd.size(); ++i) {
data_file << tfd[i].real()
<< " "
<< tfd[i].imag()
<< std::endl;
}
data_file.close();
}
int main(int argc, char** argv) {
math::csignal s;
double fe = 6000;
double f0 = 400;
int n = 30;
if (argc > 1) {
n = atoi(argv[1]);
}
for (int i=0; i<100; ++i) {
s.push_back(std::sin(2*math::pi()*50*i/100));
s.push_back(math::complex(std::sin(2*math::pi()*f0*float(i)/fe), 0));
}
math::csignal tfd = math::fft(s);
math::csignal tfd;
clock_t begin = std::clock();
for (int i=0; i<n; ++i) {
tfd = math::fft(s, 2000);
}
clock_t end = clock();
std::cout << "Time to compute " << n << " fft: "<< double(end-begin) / CLOCKS_PER_SEC << std::endl;
std::cout << "Average time: " << double(end-begin) / CLOCKS_PER_SEC / n << std::endl;
math::csignal mod;
for (int i=0; i<tfd.size(); ++i) {
double R = tfd[i].real();
double I = tfd[i].imag();
double a = std::sqrt(R*R + I*I);
mod.push_back(math::complex(float(i)/tfd.size()*fe, a));
}
create_plot_file("graph", mod);
return 0;
}

31
tests/src/math.hpp
View file

@ -4,7 +4,6 @@
#include <complex>
#include <opencv2/opencv.hpp>
#include <iterator>
#include <cmath>
namespace math {
@ -44,41 +43,45 @@ namespace math {
csignal fft_rec(const csignal& input) {
int size = input.size();
if (size == 1) {
if (size <= 1) {
return input;
} else {
csignal odd;
csignal even;
std::back_insert_iterator<csignal> odd_back_it(odd);
std::back_insert_iterator<csignal> even_back_it(even);
auto odd_back_it = std::back_inserter(odd);
auto even_back_it = std::back_inserter(even);
bool insert_in_even = false;
for (auto it = input.begin(); it != input.end(); ++it) {
if (insert_in_even) {
*even_back_it++ = *it;
*(even_back_it++) = *it;
insert_in_even = false;
} else {
*odd_back_it++ = *it;
*(odd_back_it++) = *it;
insert_in_even = true;
}
}
csignal odd_fft = fft_rec(odd);
csignal even_fft = fft_rec(even);
csignal res;
res.reserve(size);
csignal res(size, complex());
for (int k = 0; k<size/2; ++k) {
complex t = std::exp(complex(0, -2*pi()*k/size)) * odd[k];
res[k] = even[k] + t;
res[size/2+k] = even[k] - t;
for (int k=0; k<size/2; ++k) {
complex t = std::exp(complex(0, -2*pi()*k/size)) * odd_fft[k];
res[k] = even_fft[k] + t;
res[size/2+k] = even_fft[k] - t;
}
return res;
}
}
csignal fft(const csignal& input) {
int opt_size = 1 << (int)std::ceil(std::log(input.size())/std::log(2));
csignal fft(const csignal& input, int N=0) {
int opt_size;
if (N < input.size()) {
opt_size = 1 << (int)std::ceil(std::log(input.size())/std::log(2));
} else {
opt_size = 1 << (int)std::ceil(std::log(N)/std::log(2));
}
csignal sig(input);
for (int i=0; i<opt_size-input.size(); ++i) {
sig.push_back(complex(0, 0));