Added Mersenne Twister random number generator.

1 files changed, 44 insertions, 0 deletions

diff --git a/src/stable/randommersenne.cpp b/src/stable/randommersenne.cpp
new file mode 100644
index 0000000..2d9e85b
--- /dev/null
+++ b/src/stable/randommersenne.cpp
@@ -0,0 +1,44 @@
+#include "bu/randommersenne.h"
+
+Bu::RandomMersenne::RandomMersenne( int32_t iSeed ) :
+    iIndex( 0 )
+{
+    seed( iSeed );
+}
+
+Bu::RandomMersenne::~RandomMersenne()
+{
+}
+
+void Bu::RandomMersenne::seed( int32_t iSeed )
+{
+     iMt[0] = iSeed;
+     for( int j = 1; j < 624; j++ )
+     {
+         iMt[j] = 0x6c078965 * (iMt[j-1]^(iMt[j-1]>>30)) + j;
+     }
+}
+
+int32_t Bu::RandomMersenne::rand()
+{
+    if( iIndex == 0 )
+    {
+        for( int j = 0; j < 624; j++ )
+        {
+            uint32_t y = (iMt[j] & 0x80000000) + (iMt[(j+1)%624] & 0x7fffffff);
+            iMt[j] = iMt[(j+397)%624] ^ (y>>1);
+            if( (y%2) )
+                iMt[j] = iMt[j]^0x9908b0df;
+        }
+    }
+
+    uint32_t y = iMt[iIndex];
+    y = y ^ (y>>11);
+    y = y ^ ((y<<7)&0x9d2c5680);
+    y = y ^ ((y<<15)&0xefc60000);
+    y = y ^ (y>>18);
+
+    iIndex = (iIndex + 1) % 624;
+    return y;
+}
+