1 files changed, 74 insertions, 0 deletions
diff --git a/libavutil/tests/lfg.c b/libavutil/tests/lfg.c
new file mode 100644
index 0000000000..1425e026b4
--- /dev/null
+++ b/libavutil/tests/lfg.c
@@ -0,0 +1,74 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/log.h"
+#include "libavutil/timer.h"
+#include "libavutil/lfg.h"
+
+int main(void)
+{
+    int x = 0;
+    int i, j;
+    AVLFG state;
+
+    av_lfg_init(&state, 0xdeadbeef);
+    for (j = 0; j < 10000; j++) {
+        START_TIMER
+        for (i = 0; i < 624; i++) {
+            //av_log(NULL, AV_LOG_ERROR, "%X\n", av_lfg_get(&state));
+            x += av_lfg_get(&state);
+        }
+        STOP_TIMER("624 calls of av_lfg_get");
+    }
+    av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x);
+
+    /* BMG usage example */
+    {
+        double mean   = 1000;
+        double stddev = 53;
+        double samp_mean = 0.0, samp_stddev = 0.0;
+        double samp0, samp1;
+
+        av_lfg_init(&state, 42);
+
+        for (i = 0; i < 1000; i += 2) {
+            double bmg_out[2];
+            av_bmg_get(&state, bmg_out);
+            samp0 = bmg_out[0] * stddev + mean;
+            samp1 = bmg_out[1] * stddev + mean;
+            samp_mean += samp0 + samp1;
+            samp_stddev += samp0 * samp0 + samp1 * samp1;
+            av_log(NULL, AV_LOG_INFO,
+                   "%f\n%f\n",
+                   samp0,
+                   samp1);
+        }
+        /* TODO: add proper normality test */
+        samp_mean /= 1000;
+        samp_stddev /= 999;
+        samp_stddev -= (1000.0/999.0)*samp_mean*samp_mean;
+        samp_stddev = sqrt(samp_stddev);
+        av_log(NULL, AV_LOG_INFO, "sample mean  : %f\n"
+                                  "true mean    : %f\n"
+                                  "sample stddev: %f\n"
+                                  "true stddev  : %f\n",
+                                   samp_mean, mean, samp_stddev, stddev);
+    }
+
+    return 0;
+}