一个简单的fftw3例子：正弦信号的离散傅里叶变换_p=fftw_plan_dft_1d

Table of Contents

1.源代码

2.编译运行

CMakeLists.txt

编译

运行

致谢

---

1.源代码

#include <complex.h>
#include <fftw3.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <getopt.h>
#include <math.h>
 
#ifndef M_PI
#define M_PI 3.141592653589793
#endif
 
int main(int argc, char* argv[]) {
    fftw_complex *in, *out;
    fftw_plan p;
    int n = 128;
    int f = 440;
    int r = 16000;
    int m = 1;
    double a = 1.;
 
    /* Read input */
    int c;
    while (1) {
        c = getopt(argc, argv, "n:f:a:r:m:h");
        if (c==-1) break;
 
        switch (c) {
            case 'n':
                n = atoi(optarg);
                if (n<2)
                    return 1;
                break;
            case 'f':
                f = atoi(optarg);
                if (f<0)
                    return 1;
                break;
            case 'r':
                r = atoi(optarg);
                if (r<0)
                    return 1;
                break;
            case 'm':
                m = atoi(optarg);
                if (m<0)
                    return 1;
                break;
            case 'a':
                a = atof(optarg);
                if (a<1.0)
                    return 1;
                break;
            case 'h':
                printf("usage: %s [options]\n"
                        "       -n int     Integer which specifies the array length.\n"
                        "       -f int     The frequency of the intput data.\n"
                        "       -r int     The sample rate.\n"
                        "       -a float   The amplitude.\n"
                        , argv[0]);
                return 0;
        }
    }
 
    in = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * n);
 
    /* Build input */
    double dt=1./r;
    double omega=2*f*M_PI;
    printf("Input:\n");
    int i;
    for (i=0; i<n; i++) {
        double t=i*dt;
        double y = a*sin(omega*t);
        in[i] = y;
/*    printf("%f %f %f\n", t, creal(in[i]), cimag(in[i]));*/
    }
 
    out = (fftw_complex*) fftw_malloc(sizeof(fftw_complex) * n);
    p = fftw_plan_dft_1d(n, in, out, FFTW_FORWARD, FFTW_ESTIMATE);
 
    for (int j=0; j<m; j++) {
        fftw_execute(p); /* repeat as needed */
 
        /* Print output */
        printf("Output Run %i:\n", j);
        for (i=0; i<n; i++) {
            int f=i*r/n;
            double a=creal(out[i])/n;
            double b=cimag(out[i])/n;
            double r=sqrt(a*a+b*b);
            printf("%d %f\n", f, r);
        }
    }
 
    fftw_destroy_plan(p);
    fftw_free(in); fftw_free(out);
 
    return 0;
}

2.编译运行

CMakeLists.txt

cmake_minimum_required (VERSION 3.0)
project (main)
add_executable(main main.c)
 
target_link_libraries(main fftw3)
target_link_libraries(main m)
set_property(TARGET main PROPERTY C_STANDARD 99)

编译

$ cmake .
-- Configuring done
-- Generating done
-- Build files have been written to: /home/Toa/fftw3/demo1
 
$ make
[ 50%] Building C object CMakeFiles/main.dir/main.c.o
[100%] Linking C executable main.exe
[100%] Built target main

运行

$ ./main.exe -h
usage: ./main [options]
        -n int     Integer which specifies the array length.
        -f int     The frequency of the intput data.
        -r int     The sample rate.
        -a float   The amplitude.
 
$ ./main.exe -n 10 -f 100 -a 10
Input:
Output Run 0:
0 1.746801
1600 0.623929
3200 0.327044
4800 0.237484
6400 0.201983
8000 0.192089
9600 0.201983
11200 0.237484
12800 0.327044
14400 0.623929

致谢

cspiel1

https://github.com/cspiel1/fftw_demos

相关：https://github.com/JabariBooker/FFTW-Demo