Reviewers: Erik Corry, sandholm,
Message:
Small review. For use in running "benchmarks" that depend on randomness in a
deterministic way.
Description:
Added flag for seeding the random generator deterministically.
Please review this at http://codereview.chromium.org/1247003
Affected files:
M src/flag-definitions.h
M src/v8.cc
Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index
6d0b9580c0494fad5924a776094ec364c81ad13e..69acc06df38b8861fd5d7eaa5122a5d2151152a9
100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -205,6 +205,9 @@ DEFINE_bool(cleanup_ics_at_gc, true,
"Flush inline caches prior to mark compact collection.")
DEFINE_bool(cleanup_caches_in_maps_at_gc, true,
"Flush code caches in maps during mark compact cycle.")
+DEFINE_int(random_seed, 0,
+ "Default seed for initializing random generator "
+ "(0, the default, means to use system random).")
DEFINE_bool(canonicalize_object_literal_maps, true,
"Canonicalize maps for object literals.")
Index: src/v8.cc
diff --git a/src/v8.cc b/src/v8.cc
index
395401d91b2c575ccfe1ca009e403eb3d7b5cc6f..5af200348b4058e4c65075dc4d58102393f63fd9
100644
--- a/src/v8.cc
+++ b/src/v8.cc
@@ -155,6 +155,14 @@ void V8::TearDown() {
}
+static uint32_t random_seed() {
+ if (FLAG_random_seed == 0) {
+ return random();
+ }
+ return FLAG_random_seed;
+}
+
+
uint32_t V8::Random() {
// Random number generator using George Marsaglia's MWC algorithm.
static uint32_t hi = 0;
@@ -164,8 +172,8 @@ uint32_t V8::Random() {
// should ever become zero again, or if random() returns zero, we
// avoid getting stuck with zero bits in hi or lo by re-initializing
// them on demand.
- if (hi == 0) hi = random();
- if (lo == 0) lo = random();
+ if (hi == 0) hi = random_seed();
+ if (lo == 0) lo = random_seed();
// Mix the bits.
hi = 36969 * (hi & 0xFFFF) + (hi >> 16);
--
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