Adjust FFT benchmark to use same data in each iteration.

app/benchmark_fft/main.cpp

@@ -43,8 +43,9 @@ int main(int argc, char **argv) {
   string full_directory = directory + "/PLS_v3/";
   benchmark_runner runner{full_directory, test_name};
 
-  fft::complex_vector data = fft::generate_input();
-  fft::complex_vector swap_array(data.size());
+  fft::complex_vector data(fft::SIZE);
+  fft::complex_vector swap_array(fft::SIZE);
+  fft::fill_input(data);
 
   static_scheduler_memory<MAX_NUM_THREADS,
                           MAX_NUM_TASKS,
@@ -55,7 +56,9 @@ int main(int argc, char **argv) {
     scheduler.perform_work([&]() {
       pls_conquer(data.begin(), swap_array.begin(), fft::SIZE);;
     });
-  }, fft::NUM_WARMUP_ITERATIONS);
+  }, fft::NUM_WARMUP_ITERATIONS, [&]() {
+    fft::fill_input(data); // Reset data before each run
+  });
   runner.commit_results(true);
 
   return 0;

extern/benchmark_base/include/benchmark_base/fft.h

@@ -16,7 +16,7 @@ const int NUM_WARMUP_ITERATIONS = 100;
 const int RECURSIVE_CUTOFF = 32;
 typedef std::vector<std::complex<double>> complex_vector;
 
-complex_vector generate_input();
+void fill_input(fft::complex_vector &data);
 
 void divide(complex_vector::iterator data, complex_vector::iterator swap_array, int n);
 void conquer(complex_vector::iterator data, complex_vector::iterator swap_array, int n);

extern/benchmark_base/src/fft.cpp

@@ -4,19 +4,10 @@ namespace comparison_benchmarks {
 namespace base {
 namespace fft {
 
-complex_vector generate_input() {
-  std::vector<double> known_frequencies{2, 11, 52, 88, 256};
-  fft::complex_vector data(SIZE);
-  // Set our input data to match a time series of the known_frequencies.
-  // When applying fft to this time-series we should find these frequencies.
-  for (int i = 0; i < SIZE; i++) {
-    data[i] = std::complex<double>(0.0, 0.0);
-    for (auto frequencie : known_frequencies) {
-      data[i] += sin(2 * M_PI * frequencie * i / SIZE);
-    }
+void fill_input(fft::complex_vector &data) {
+  for (size_t i = 0; i < data.size(); i++) {
+    data[i] = std::complex<double>(sin(i), 0.0);
   }
-
-  return data;
 }
 
 void divide(complex_vector::iterator data, complex_vector::iterator tmp_odd_elements, int n) {

extern/benchmark_runner/benchmark_runner.h

@@ -65,14 +65,19 @@ class benchmark_runner {
     times_.emplace_back(time);
   }
 
-  void run_iterations(int count, function<void(void)> f, int warmup_count) {
+  void run_iterations(int count,
+                      const function<void(void)> measure,
+                      int warmup_count,
+                      const function<void(void)> prepare = []() {}) {
     for (int i = 0; i < warmup_count; i++) {
-      f();
+      prepare();
+      measure();
     }
 
     for (int i = 0; i < count; i++) {
+      prepare();
       start_iteration();
-      f();
+      measure();
       end_iteration();
     }
   }