lib: Add a tiny utility function to compute averages

The master plan would be to get a bit more stats in it, at least the
standard deviation and confidence interval. Just need the average for
now.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>

lib/tests/.gitignore

@@ -8,4 +8,5 @@ igt_no_subtest
 igt_segfault
 igt_simple_test_subtests
 igt_simulation
+igt_stats
 igt_timeout

lib/tests/Makefile.sources

@@ -6,6 +6,7 @@ check_PROGRAMS = \
 	igt_no_subtest \
 	igt_simulation \
 	igt_simple_test_subtests \
+	igt_stats \
 	igt_timeout \
 	igt_invalid_subtest_name \
 	igt_segfault \

lib/tests/igt_stats.c

@@ -0,0 +1,49 @@
+/*
+ * Copyright © 2015 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+#include "igt_core.h"
+#include "igt_stats.h"
+
+static void test_average(void)
+{
+	igt_stats_t stats;
+	double average;
+
+	igt_stats_init(&stats, 5);
+
+	igt_stats_push(&stats, 2);
+	igt_stats_push(&stats, 4);
+	igt_stats_push(&stats, 6);
+	igt_stats_push(&stats, 8);
+	igt_stats_push(&stats, 10);
+
+	average = igt_stats_get_average(&stats);
+
+	igt_assert(average == (2 + 4 + 6 + 8 + 10) / 5.);
+}
+
+igt_simple_main
+{
+	test_average();
+}