*** empty log message ***

random_source.h

@@ -1,6 +1,8 @@
 #ifndef RANDOM_GEN_H_
 #define RANDOM_GEN_H_
 
+#include "assert_helpers.h"
+
 /**
  * Simple pseudo-random linear congruential generator, a la Numerical
  * Recipes.
@@ -26,7 +28,7 @@ class RandomSource {
 		last = a * last + c;
 		ret = last >> 16;
 		last = a * last + c;
-		ret |= last;
+		ret ^= last;
 		lastOff = 0;
 		return ret;
 	}

random_test.cpp

@@ -0,0 +1,48 @@
+/*
+ * random_test.cpp
+ *
+ *  Created on: Dec 11, 2009
+ *      Author: Ben Langmead
+ */
+
+#include <iostream>
+#include <string.h>
+#include "random_source.h"
+
+using namespace std;
+
+int main(void) {
+	RandomSource rand;
+	rand.init(0);
+	uint32_t ts[32];
+	memset(ts, 0, 32*sizeof(uint32_t));
+	uint32_t r = rand.nextU32();
+	cout << "Without reseeding:" << endl;
+	for(int i = 0; i < 10000; i++) {
+		uint32_t nr = rand.nextU32();
+		for(int j = 0; j < 32; j++) {
+			if(((r >> j) & 1) != ((nr >> j) & 1)) {
+				ts[j]++;
+			}
+		}
+	}
+	for(int j = 0; j < 32; j++) {
+		cout << ts[j] << endl;
+	}
+	memset(ts, 0, 32*sizeof(uint32_t));
+	rand.init(0);
+	r = rand.nextU32();
+	cout << "With reseeding:" << endl;
+	for(int i = 0; i < 10000; i++) {
+		rand.init(i+1);
+		uint32_t nr = rand.nextU32();
+		for(int j = 0; j < 32; j++) {
+			if(((r >> j) & 1) != ((nr >> j) & 1)) {
+				ts[j]++;
+			}
+		}
+	}
+	for(int j = 0; j < 32; j++) {
+		cout << ts[j] << endl;
+	}
+}