Merge branch 'stclib:master' into modifiedHEADmodified

1 files changed, 68 insertions, 0 deletions

diff --git a/misc/examples/hashmaps/birthday.c b/misc/examples/hashmaps/birthday.c
new file mode 100644
index 00000000..4742cb45
--- /dev/null
+++ b/misc/examples/hashmaps/birthday.c
@@ -0,0 +1,68 @@
+#include <math.h>
+#include <stdio.h>
+#include <time.h>
+#include <stc/crand.h>
+
+#define i_tag ic
+#define i_key uint64_t
+#define i_val int
+#include <stc/cmap.h>
+
+static uint64_t seed = 12345;
+
+static void test_repeats(void)
+{
+    enum {BITS = 46, BITS_TEST = BITS/2 + 2};
+    static const uint64_t N = 1ull << BITS_TEST;
+    static const uint64_t mask = (1ull << BITS) - 1;
+
+    printf("birthday paradox: value range: 2^%d, testing repeats of 2^%d values\n", BITS, BITS_TEST);
+    crand_t rng = crand_init(seed);
+
+    cmap_ic m = cmap_ic_with_capacity(N);
+    c_forrange (i, N) {
+        uint64_t k = crand_u64(&rng) & mask;
+        int v = cmap_ic_insert(&m, k, 0).ref->second += 1;
+        if (v > 1) printf("repeated value %" PRIu64 " (%d) at 2^%d\n",
+                          k, v, (int)log2((double)i));
+    }
+    cmap_ic_drop(&m);
+}
+
+#define i_key uint32_t
+#define i_val uint64_t
+#define i_tag x
+#include <stc/cmap.h>
+
+void test_distribution(void)
+{
+    enum {BITS = 26};
+    printf("distribution test: 2^%d values\n", BITS);
+    crand_t rng = crand_init(seed);
+    const size_t N = 1ull << BITS ;
+
+    cmap_x map = {0};
+    c_forrange (N) {
+        uint64_t k = crand_u64(&rng);
+        cmap_x_insert(&map, k & 0xf, 0).ref->second += 1;
+    }
+
+    uint64_t sum = 0;
+    c_foreach (i, cmap_x, map) sum += i.ref->second;
+    sum /= (uint64_t)map.size;
+
+    c_foreach (i, cmap_x, map) {
+        printf("%4" PRIu32 ": %" PRIu64 " - %" PRIu64 ": %11.8f\n",
+                i.ref->first, i.ref->second, sum,
+                (1.0 - (double)i.ref->second / (double)sum));
+    }
+
+    cmap_x_drop(&map);
+}
+
+int main(void)
+{
+    seed = (uint64_t)time(NULL);
+    test_distribution();
+    test_repeats();
+}