tally: new module for tallying numbers.

[ccan] / ccan / tally / test / run-median.c

diff --git a/ccan/tally/test/run-median.c b/ccan/tally/test/run-median.c
new file mode 100644 (file)
index 0000000..f461c2e
--- /dev/null
+++ b/ccan/tally/test/run-median.c
@@ -0,0 +1,45 @@
+#include <ccan/tally/tally.c>
+#include <ccan/tap/tap.h>
+
+int main(void)
+{
+       int i;
+       struct tally *tally = tally_new(100);
+       ssize_t min, max, median;
+       size_t err;
+
+       max = (ssize_t)~(1ULL << (sizeof(max)*CHAR_BIT - 1));
+       min = (ssize_t)(1ULL << (sizeof(max)*CHAR_BIT - 1));
+
+       plan_tests(100*2 + 100*2 + 100*2);
+       /* Simple median test: should always be around 0. */
+       for (i = 0; i < 100; i++) {
+               tally_add(tally, i);
+               tally_add(tally, -i);
+               median = tally_approx_median(tally, &err);
+               ok1(err <= 4);
+               ok1(median - (ssize_t)err <= 0 && median + (ssize_t)err >= 0);
+       }
+
+       /* Works for big values too... */
+       for (i = 0; i < 100; i++) {
+               tally_add(tally, max - i);
+               tally_add(tally, min + 1 + i);
+               median = tally_approx_median(tally, &err);
+               /* Error should be < 100th of max - min. */
+               ok1(err <= max / 100 * 2);
+               ok1(median - (ssize_t)err <= 0 && median + (ssize_t)err >= 0);
+       }
+       free(tally);
+
+       tally = tally_new(10);
+       for (i = 0; i < 100; i++) {
+               tally_add(tally, i);
+               median = tally_approx_median(tally, &err);
+               ok1(err <= i / 10 + 1);
+               ok1(median - (ssize_t)err <= i/2
+                   && median + (ssize_t)err >= i/2);
+       }
+
+       return exit_status();
+}