star-sp

commit 4089873f6642a7bbe4fb2a0ba266a064ceb8aa90
parent a370aae963dfbab4aab5adba378736dc29afe6ac
Author: Vincent Forest <vincent.forest@meso-star.com>
Date:   Wed,  2 Dec 2020 11:16:18 +0100

Comment the tests on the RNG proxy cache

Diffstat:
M
src/test_ssp_rng_proxy.c
 | 
38
++++++++++++++++++++++++++++++++++++--

1 file changed, 36 insertions(+), 2 deletions(-)
diff --git a/src/test_ssp_rng_proxy.c b/src/test_ssp_rng_proxy.c
@@ -468,23 +468,56 @@ test_cache(void)
   size_t i;
 
   /* Create a proxy with a very small sequence size of 2 RNs per bucket in
-   * order to maximize the number of cached states. */
+   * order to maximize the number of cached states. Furthermore, use the
+   * Mersenne Twister RNG type since its internal state is the greatest one of
+   * the proposed builtin type and is thus the one that will fill quickly the
+   * cache stream. */
   args.type = &ssp_rng_mt19937_64;
   args.sequence_size = 4;
   args.sequence_pitch = 4;
   args.nbuckets = 2;
-  CHK(ssp_rng_proxy_create2(NULL, &args, &proxy) == RES_OK);
 
+  /* Simply test that the RNs generated by the proxy are the same thant the
+   * ones generated by a regular RNG. Since each RNG invocation are
+   * interleaved, the cache pressure is very low, at most 1 RNG state is
+   * cached. */
+  CHK(ssp_rng_proxy_create2(NULL, &args, &proxy) == RES_OK);
   CHK(ssp_rng_proxy_create_rng(proxy, 0, &rng0) == RES_OK);
   CHK(ssp_rng_proxy_create_rng(proxy, 1, &rng1) == RES_OK);
+  CHK(ssp_rng_create(NULL, &ssp_rng_mt19937_64, &rng) == RES_OK);
+  FOR_EACH(i, 0, nrands*2) {
+    if((i / 2) % 2) {
+      CHK(ssp_rng_get(rng1) == ssp_rng_get(rng));
+    } else {
+      CHK(ssp_rng_get(rng0) == ssp_rng_get(rng));
+    }
+  }
+  CHK(ssp_rng_proxy_ref_put(proxy) == RES_OK);
+  CHK(ssp_rng_ref_put(rng0) == RES_OK);
+  CHK(ssp_rng_ref_put(rng1) == RES_OK);
+  CHK(ssp_rng_ref_put(rng) == RES_OK);
 
+  CHK(ssp_rng_proxy_create2(NULL, &args, &proxy) == RES_OK);
+  CHK(ssp_rng_proxy_create_rng(proxy, 0, &rng0) == RES_OK);
+  CHK(ssp_rng_proxy_create_rng(proxy, 1, &rng1) == RES_OK);
   CHK(ssp_rng_create(NULL, &ssp_rng_mt19937_64, &rng) == RES_OK);
+
+  /* Generate several RNs for the first RNG only to make under pressure the
+   * cache stream of 'rng1'. The cache stream limit is set to 32 MB and the
+   * size of a Mersenne Twister RNG state is greater than 6 KB. Consquently,
+   * ~5500 RNG states will exceed the cache stream, i.e. 5500*2 = 11000
+   * random generations (since there is 2 RNs per bucket). Above this limit,
+   * 'rng1' will not rely anymore on the proxy RNG to manage its state.
+   *
+   * For both RNGs, ensure that the generated RNs are the expected ones by
+   * comparing them to the ones generated by a regular RNG */
   FOR_EACH(i, 0, nrands) {
     CHK(ssp_rng_get(rng0) == ssp_rng_get(rng));
     if(i % 2) CHK(ssp_rng_discard(rng, 2) == RES_OK);
   }
   CHK(ssp_rng_ref_put(rng) == RES_OK);
 
+  /* Check the cache mechanisme of rng1 */
   CHK(ssp_rng_create(NULL, &ssp_rng_mt19937_64, &rng) == RES_OK);
   CHK(ssp_rng_discard(rng, 2) == RES_OK);
   FOR_EACH(i, 0, nrands) {
@@ -496,6 +529,7 @@ test_cache(void)
   CHK(ssp_rng_proxy_ref_put(proxy) == RES_OK);
   CHK(ssp_rng_ref_put(rng0) == RES_OK);
   CHK(ssp_rng_ref_put(rng1) == RES_OK);
+
 }
 
 int