Thread-safe, platform-agnostic randomizer.

Some places in mert use srandom()/random(), but these are POSIX-specific.
The standard alternative, srand()/rand(), is not thread-safe.  This module
wraps srand()/rand() in mutexes (very short-lived, so should not cost much)
so that it relies on just Boost and the C standard library, not on a Unix-like
environment.

This may reduce the width of the random numbers on some platforms: it goes
from "long int" to just "int".  If that is a problem, we may have to use
Boost's randomizer utilities, or eventually, the C++ ones.

4 files changed, 12 insertions, 8 deletions

diff --git a/mert/Data.cpp b/mert/Data.cpp
index 49c1239e5..428886b99 100644
--- a/mert/Data.cpp
+++ b/mert/Data.cpp
@@ -17,6 +17,7 @@
 #include "util/exception.hh"
 
 #include "util/file_piece.hh"
+#include "util/random.hh"
 #include "util/tokenize_piece.hh"
 #include "util/string_piece.hh"
 #include "FeatureDataIterator.h"
@@ -286,7 +287,7 @@ void Data::createShards(size_t shard_count, float shard_size, const string& scor
     } else {
       //create shards by randomly sampling
       for (size_t i = 0; i < floor(shard_size+0.5); ++i) {
-        shard_contents.push_back(rand() % data_size);
+        shard_contents.push_back(util::rand_int() % data_size);
       }
     }
 
diff --git a/mert/Point.cpp b/mert/Point.cpp
index 55dc6a6b2..562249492 100644
--- a/mert/Point.cpp
+++ b/mert/Point.cpp
@@ -3,6 +3,7 @@
 #include <cmath>
 #include <cstdlib>
 #include "util/exception.hh"
+#include "util/random.hh"
 #include "FeatureStats.h"
 #include "Optimizer.h"
 
@@ -58,8 +59,8 @@ void Point::Randomize()
   UTIL_THROW_IF(m_max.size() != Point::m_dim, util::Exception, "Error");
 
   for (unsigned int i = 0; i < size(); i++) {
-    operator[](i) = m_min[i] +
-                    static_cast<float>(random()) / static_cast<float>(RAND_MAX) * (m_max[i] - m_min[i]);
+    const float scale = (m_max[i] - m_min[i]) / float(RAND_MAX);
+    operator[](i) = m_min[i] + util::rand_int() * scale;
   }
 }
 
diff --git a/mert/evaluator.cpp b/mert/evaluator.cpp
index 026abf397..61775a354 100644
--- a/mert/evaluator.cpp
+++ b/mert/evaluator.cpp
@@ -16,6 +16,7 @@
 #include "Timer.h"
 #include "Util.h"
 #include "Data.h"
+#include "util/random.hh"
 
 using namespace std;
 using namespace MosesTuning;
@@ -94,7 +95,7 @@ void EvaluatorUtil::evaluate(const string& candFile, int bootstrap, bool nbest_i
     for (int i = 0; i < bootstrap; ++i) {
       ScoreData scoredata(g_scorer);
       for (int j = 0; j < n; ++j) {
-        int randomIndex = random() % n;
+        int randomIndex = util::rand_int() % n;
         scoredata.add(entries[randomIndex], j);
       }
       g_scorer->setScoreData(&scoredata);
@@ -284,10 +285,10 @@ void InitSeed(const ProgramOption *opt)
 {
   if (opt->has_seed) {
     cerr << "Seeding random numbers with " << opt->seed << endl;
-    srandom(opt->seed);
+    util::rand_int_init(opt->seed);
   } else {
     cerr << "Seeding random numbers with system clock " << endl;
-    srandom(time(NULL));
+    util::rand_int_init();
   }
 }
 
diff --git a/mert/mert.cpp b/mert/mert.cpp
index 275aa7b09..e79ba7c6b 100644
--- a/mert/mert.cpp
+++ b/mert/mert.cpp
@@ -24,6 +24,7 @@
 #include "Types.h"
 #include "Timer.h"
 #include "Util.h"
+#include "util/random.hh"
 
 #include "moses/ThreadPool.h"
 
@@ -289,10 +290,10 @@ int main(int argc, char **argv)
 
   if (option.has_seed) {
     cerr << "Seeding random numbers with " << option.seed << endl;
-    srandom(option.seed);
+    util::rand_int_init(option.seed);
   } else {
     cerr << "Seeding random numbers with system clock " << endl;
-    srandom(time(NULL));
+    util::rand_int_init();
   }
 
   if (option.sparse_weights_file.size()) ++option.pdim;