Add FFTW3 benchmark

benches/Makefile

@@ -0,0 +1,10 @@
+CC = gcc
+CFLAGS = -Wall -Wextra -O3 -march=native
+LIBS = -lfftw3 -lm
+
+program: main.c
+	$(CC) $(CFLAGS) -o bench_fftw main.c $(LIBS)
+
+clean:
+	rm -f program
+

benches/README.md

@@ -1 +1 @@
-Benchmarking
+# BENCHMARKING

benches/main.c

@@ -0,0 +1,36 @@
+#include <stdlib.h>
+#include <math.h>
+#include <fftw3.h>
+#include <time.h>
+
+int main(int argc, char** argv) {
+    if (argc != 2) {
+        fprintf(stderr, "Usage: %s <n>\n", argv[0]);
+        return EXIT_FAILURE;
+    }
+    long n = strtol(argv[1], NULL, 0);
+    printf("%ld\n", n);
+
+    int N = 1 << n;
+    fftw_complex* in = fftw_alloc_complex(N);
+
+    double a = 1.0;
+    for (int i = 0; i < N; i++) {
+        in[i][0] = ((double)rand()/(double)(RAND_MAX)) * a;
+        in[i][1] = ((double)rand()/(double)(RAND_MAX)) * a;
+    }
+
+    double tic = clock();
+    fftw_plan p = fftw_plan_dft_1d(N, in, in, FFTW_FORWARD, FFTW_ESTIMATE);
+    fftw_execute(p);
+    double toc = clock();
+
+    double elapsed = ((double)(toc - tic) / CLOCKS_PER_SEC) * 1000000;
+    printf("%f\n", elapsed);
+    fftw_free(in);
+    fftw_destroy_plan(p);
+    fftw_cleanup();
+
+    return EXIT_SUCCESS;
+}
+