changeset 27:4fa5f3f883a2

Add native-code version for comparison

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/fft/native.cpp	Wed Oct 07 21:28:09 2015 +0100
@@ -0,0 +1,59 @@
+
+#include <bqfft/FFT.h>
+
+#include <vector>
+#include <iostream>
+#include <cmath>
+#include <chrono>
+
+using namespace std;
+using namespace breakfastquay;
+
+int main(int argc, char **argv)
+{
+    vector<int> sizes { 512, 2048 };
+
+    int iterations = 2000;
+    int times = 100;
+
+    for (auto size: sizes) {
+
+	FFT fft(size);
+	double total = 0.0;
+
+	auto start = chrono::high_resolution_clock::now();
+
+	for (int ti = 0; ti < times; ++ti) {
+	    
+	    total = 0.0;
+
+	    for (int i = 0; i < iterations; ++i) {
+
+		vector<double> ri(size), ro(size/2+1), io(size/2+1);
+		for (int j = 0; j < size; ++j) {
+		    ri[j] = (j % 2) / 4.0;
+		}
+
+		fft.forward(ri.data(), ro.data(), io.data());
+
+		for (int j = 0; j <= size/2; ++j) {
+		    total += sqrt(ro[j] * ro[j] + io[j] * io[j]);
+		}
+
+		// synthesise the conjugate half
+		for (int j = 1; j < size/2; ++j) {
+		    total += sqrt(ro[j] * ro[j] + io[j] * io[j]);
+		}
+	    }
+	}
+
+	auto end = chrono::high_resolution_clock::now();
+
+	double ms = chrono::duration<double, milli>(end - start).count() / times;
+	
+	cerr << "for size " << size << ", iterations " << iterations
+	     << ": total = " << total << ", time = "
+	     << ms << " ms (" << (iterations / (ms / 1000.0)) << " itr/sec)" << endl;
+    }
+}
+