Add cross-platform randomizer module.

The code uses two mechanisms for generating random numbers: srand()/rand(),
which is not thread-safe, and srandom()/random(), which is POSIX-specific.

Here I add a util/random.cc module that centralizes these calls, and unifies
some common usage patterns.  If the implementation is not good enough, we can
now change it in a single place.

To keep things simple, this uses the portable srand()/rand() but protects them
with a lock to avoid concurrency problems.

The hard part was to keep the regression tests passing: they rely on fixed
sequences of random numbers, so a small code change could break them very
thoroughly.  Util::rand(), for wide types like size_t, calls std::rand() not
once but twice.  This behaviour was generalized into utils::wide_rand() and
friends.

1 files changed, 2 insertions, 2 deletions

diff --git a/mert/mert.cpp b/mert/mert.cpp
index e79ba7c6b..82b4cc34d 100644
--- a/mert/mert.cpp
+++ b/mert/mert.cpp
@@ -290,10 +290,10 @@ int main(int argc, char **argv)
 
   if (option.has_seed) {
     cerr << "Seeding random numbers with " << option.seed << endl;
-    util::rand_int_init(option.seed);
+    util::rand_init(option.seed);
   } else {
     cerr << "Seeding random numbers with system clock " << endl;
-    util::rand_int_init();
+    util::rand_init();
   }
 
   if (option.sparse_weights_file.size()) ++option.pdim;