Add a benchmarker for the sample converters.

Makefile

@@ -39,7 +39,7 @@ faup1090: faup1090.o anet.o mode_ac.o mode_s.o net_io.o crc.o stats.o cpr.o icao
 	$(CC) -g -o $@ $^ $(LDFLAGS) $(LIBS)
 
 clean:
-	rm -f *.o compat/clock_gettime/*.o compat/clock_nanosleep/*.o dump1090 view1090 faup1090 cprtests crctests
+	rm -f *.o compat/clock_gettime/*.o compat/clock_nanosleep/*.o dump1090 view1090 faup1090 cprtests crctests convert_benchmark
 
 test: cprtests
 	./cprtests
@@ -49,3 +49,9 @@ cprtests: cpr.o cprtests.o
 
 crctests: crc.c crc.h
 	$(CC) $(CPPFLAGS) $(CFLAGS) -g -DCRCDEBUG -o $@ $<
+
+benchmarks: convert_benchmark
+	./convert_benchmark
+
+convert_benchmark: convert_benchmark.o convert.o util.o
+	$(CC) $(CPPFLAGS) $(CFLAGS) -g -o $@ $^ -lm

convert_benchmark.c

@@ -0,0 +1,88 @@
+#include "dump1090.h"
+
+static uint8_t *testdata_uc8;
+static uint16_t *testdata_sc16;
+static uint16_t *testdata_sc16q11;
+static uint16_t *outdata;
+
+void prepare()
+{
+    srand(1);
+
+    testdata_uc8 = calloc(MODES_MAG_BUF_SAMPLES, 2);
+    testdata_sc16 = calloc(MODES_MAG_BUF_SAMPLES, 4);
+    testdata_sc16q11 = calloc(MODES_MAG_BUF_SAMPLES, 4);
+    outdata = calloc(MODES_MAG_BUF_SAMPLES, sizeof(uint16_t));
+
+    for (unsigned i = 0; i < MODES_MAG_BUF_SAMPLES; ++i) {
+        double I = 2.0 * rand() / (RAND_MAX + 1.0) - 1.0;
+        double Q = 2.0 * rand() / (RAND_MAX + 1.0) - 1.0;
+
+        testdata_uc8[i*2] = (uint8_t) (I * 128 + 128);
+        testdata_uc8[i*2+1] = (uint8_t) (Q * 128 + 128);
+
+        testdata_sc16[i*2] = htole16( (int16_t) (I * 32768.0) );
+        testdata_sc16[i*2+1] = htole16( (int16_t) (Q * 32768.0) );
+
+        testdata_sc16q11[i*2] = htole16( (int16_t) (I * 2048.0) );
+        testdata_sc16q11[i*2+1] = htole16( (int16_t) (Q * 2048.0) );
+    }
+}
+
+void test(const char *what, input_format_t format, void *data, double sample_rate, bool filter_dc) {
+    fprintf(stderr, "Benchmarking: %s ", what);
+
+    struct converter_state *state;
+    iq_convert_fn converter = init_converter(format, sample_rate, filter_dc, &state);
+    if (!converter) {
+        fprintf(stderr, "Can't initialize converter\n");
+        return;
+    }
+
+    struct timespec total = { 0, 0 };
+    int iterations = 0;
+
+    // Run it once to force init.
+    converter(data, outdata, MODES_MAG_BUF_SAMPLES, state, NULL, NULL);
+
+    while (total.tv_sec < 5) {
+        fprintf(stderr, ".");
+
+        struct timespec start;
+        start_cpu_timing(&start);
+
+        for (int i = 0; i < 10; ++i) {
+            converter(data, outdata, MODES_MAG_BUF_SAMPLES, state, NULL, NULL);
+        }
+
+        end_cpu_timing(&start, &total);
+        iterations++;
+    }
+
+    fprintf(stderr, "\n");
+    cleanup_converter(state);
+
+    double samples = 10.0 * iterations * MODES_MAG_BUF_SAMPLES;
+    double nanos = total.tv_sec * 1e9 + total.tv_nsec;
+    fprintf(stderr, "  %.2fM samples in %.6f seconds\n",
+            samples / 1e6, nanos / 1e9);
+    fprintf(stderr, "  %.2fM samples/second\n",
+            samples / nanos * 1e3);
+}
+
+int main(int argc, char **argv)
+{
+    MODES_NOTUSED(argc);
+    MODES_NOTUSED(argv);
+
+    prepare();
+
+    test("SC16Q11, DC", INPUT_SC16Q11, testdata_sc16q11, 2400000, true);
+    test("SC16Q11, no DC", INPUT_SC16Q11, testdata_sc16q11, 2400000, false);
+
+    test("UC8, DC", INPUT_UC8, testdata_uc8, 2400000, true);
+    test("UC8, no DC", INPUT_UC8, testdata_uc8, 2400000, false);
+
+    test("SC16, DC", INPUT_SC16, testdata_sc16, 2400000, true);
+    test("SC16, no DC", INPUT_SC16, testdata_sc16, 2400000, false);
+}