From 962abebbf215337ffe4ec227d58b9e8b458f12c5 Mon Sep 17 00:00:00 2001
From: Charles Otto <ottochar@gmail.com>
Date: Mon, 2 Feb 2015 18:20:23 -0800
Subject: [PATCH] Replace use of rand() in RandSample, this was resulting in poor results from RndSubspace on windows

---
 openbr/core/common.cpp | 15 +++++++++++++--
 openbr/core/common.h   | 12 +++++-------
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/openbr/core/common.cpp b/openbr/core/common.cpp
index d6c445a..acc8b49 100644
--- a/openbr/core/common.cpp
+++ b/openbr/core/common.cpp
@@ -16,21 +16,32 @@
 
 #include "common.h"
 #include <QMutex>
+#include <RandomLib\Random.hpp>
 
 using namespace std;
 
+static RandomLib::Random g_rand;
+static QMutex rngLock;
+
 /**** GLOBAL ****/
 void Common::seedRNG() {
-    static QMutex seedControl;
-    QMutexLocker lock(&seedControl);
+    QMutexLocker lock(&rngLock);
 
     static bool seeded = false;
     if (!seeded) {
         srand(0); // We seed with 0 instead of time(NULL) to have reproducible randomness
         seeded = true;
+        g_rand.Reseed(0);
     }
 }
 
+double Common::randN()
+{
+    QMutexLocker lock(&rngLock);
+
+    return g_rand.FloatN();
+}
+
 QList<int> Common::RandSample(int n, int max, int min, bool unique)
 {
     QList<int> samples; samples.reserve(n);
diff --git a/openbr/core/common.h b/openbr/core/common.h
index 1a9be82..843dc96 100644
--- a/openbr/core/common.h
+++ b/openbr/core/common.h
@@ -220,6 +220,9 @@ double KernelDensityEstimation(const V<T> &vals, double x, double h)
     return y / (vals.size() * h);
 }
 
+// Return a random number, uniformly distributed over 0,1
+double randN();
+
 /*!
  * \brief Returns a vector of n integers sampled in the range <min, max].
  *
@@ -236,19 +239,14 @@ QList<int> RandSample(int n, const QSet<int> &values, bool unique = false);
 template <typename T>
 QList<int> RandSample(int n, const QList<T> &weights, bool unique = false)
 {
-    static bool seeded = false;
-    if (!seeded) {
-        srand(time(NULL));
-        seeded = true;
-    }
-
     QList<T> cdf = CumSum(weights);
     for (int i=0; i<cdf.size(); i++) // Normalize cdf
         cdf[i] = cdf[i] / cdf.last();
 
     QList<int> samples; samples.reserve(n);
     while (samples.size() < n) {
-        T r = (T)rand() / (T)RAND_MAX;
+        T r = randN();
+
         for (int j=0; j<weights.size(); j++) {
             if ((r >= cdf[j]) && (r <= cdf[j+1])) {
                 if (!unique || !samples.contains(j))
--
libgit2 0.21.4