Fix possible overflow and biais in integer random generator

1 files changed, 35 insertions, 8 deletions

diff --git a/test/rand.cpp b/test/rand.cpp
index eeec34191..51cf01773 100644
--- a/test/rand.cpp
+++ b/test/rand.cpp
@@ -9,6 +9,8 @@
 
 #include "main.h"
 
+typedef long long int64;
+
 template<typename Scalar> Scalar check_in_range(Scalar x, Scalar y)
 {
   Scalar r = internal::random<Scalar>(x,y);
@@ -35,31 +37,49 @@ template<typename Scalar> void check_all_in_range(Scalar x, Scalar y)
   VERIFY( (mask>0).all() );
 }
 
+template<typename Scalar> void check_histogram(Scalar x, Scalar y, int bins)
+{
+  Array<int,1,Dynamic> hist(bins);
+  hist.fill(0);
+  int f = 100000;
+  int n = bins*f;
+  int64 range = int64(y)-int64(x);
+  int divisor = int((range+1)/bins);
+  assert(((range+1)%bins)==0);
+  for(int k=0; k<n; ++k)
+  {
+    Scalar r = check_in_range(x,y);
+    hist( int((int64(r)-int64(x))/divisor) )++;
+  }
+  VERIFY( (((hist.cast<double>()/double(f))-1.0).abs()<0.02).all() );
+}
+
 void test_rand()
 {
   long long_ref = NumTraits<long>::highest()/10;
   signed char char_offset = (std::min)(g_repeat,64);
   signed char short_offset = (std::min)(g_repeat,16000);
-  
-  for(int i = 0; i < g_repeat*10; i++) {
+
+  for(int i = 0; i < g_repeat*10000; i++) {
     CALL_SUBTEST(check_in_range<float>(10,11));
     CALL_SUBTEST(check_in_range<float>(1.24234523,1.24234523));
     CALL_SUBTEST(check_in_range<float>(-1,1));
     CALL_SUBTEST(check_in_range<float>(-1432.2352,-1432.2352));
-    
+
     CALL_SUBTEST(check_in_range<double>(10,11));
     CALL_SUBTEST(check_in_range<double>(1.24234523,1.24234523));
     CALL_SUBTEST(check_in_range<double>(-1,1));
     CALL_SUBTEST(check_in_range<double>(-1432.2352,-1432.2352));
-    
+
     CALL_SUBTEST(check_in_range<int>(0,-1));
     CALL_SUBTEST(check_in_range<short>(0,-1));
     CALL_SUBTEST(check_in_range<long>(0,-1));
     CALL_SUBTEST(check_in_range<int>(-673456,673456));
+    CALL_SUBTEST(check_in_range<int>(-RAND_MAX+10,RAND_MAX-10));
     CALL_SUBTEST(check_in_range<short>(-24345,24345));
     CALL_SUBTEST(check_in_range<long>(-long_ref,long_ref));
   }
-  
+
   CALL_SUBTEST(check_all_in_range<signed char>(11,11));
   CALL_SUBTEST(check_all_in_range<signed char>(11,11+char_offset));
   CALL_SUBTEST(check_all_in_range<signed char>(-5,5));
@@ -67,25 +87,32 @@ void test_rand()
   CALL_SUBTEST(check_all_in_range<signed char>(-126,-126+char_offset));
   CALL_SUBTEST(check_all_in_range<signed char>(126-char_offset,126));
   CALL_SUBTEST(check_all_in_range<signed char>(-126,126));
-  
+
   CALL_SUBTEST(check_all_in_range<short>(11,11));
   CALL_SUBTEST(check_all_in_range<short>(11,11+short_offset));
   CALL_SUBTEST(check_all_in_range<short>(-5,5));
   CALL_SUBTEST(check_all_in_range<short>(-11-short_offset,-11));
   CALL_SUBTEST(check_all_in_range<short>(-24345,-24345+short_offset));
   CALL_SUBTEST(check_all_in_range<short>(24345,24345+short_offset));
-  
+
   CALL_SUBTEST(check_all_in_range<int>(11,11));
   CALL_SUBTEST(check_all_in_range<int>(11,11+g_repeat));
   CALL_SUBTEST(check_all_in_range<int>(-5,5));
   CALL_SUBTEST(check_all_in_range<int>(-11-g_repeat,-11));
   CALL_SUBTEST(check_all_in_range<int>(-673456,-673456+g_repeat));
   CALL_SUBTEST(check_all_in_range<int>(673456,673456+g_repeat));
-  
+
   CALL_SUBTEST(check_all_in_range<long>(11,11));
   CALL_SUBTEST(check_all_in_range<long>(11,11+g_repeat));
   CALL_SUBTEST(check_all_in_range<long>(-5,5));
   CALL_SUBTEST(check_all_in_range<long>(-11-g_repeat,-11));
   CALL_SUBTEST(check_all_in_range<long>(-long_ref,-long_ref+g_repeat));
   CALL_SUBTEST(check_all_in_range<long>( long_ref, long_ref+g_repeat));
+
+  CALL_SUBTEST(check_histogram<int>(-5,5,11));
+  int bins = 100;
+  CALL_SUBTEST(check_histogram<int>(-3333,-3333+bins*(3333/bins)-1,bins));
+  bins = 1000;
+  CALL_SUBTEST(check_histogram<int>(-RAND_MAX+10,-RAND_MAX+10+bins*(RAND_MAX/bins)-1,bins));
+  CALL_SUBTEST(check_histogram<int>(-RAND_MAX+10,-int64(RAND_MAX)+10+bins*(2*int64(RAND_MAX)/bins)-1,bins));
 }