Merge pull request #2312 from gmaxwell/random_random

ApproximateBestSubset internal RNG to prevent degenerate behavior.

1 files changed, 20 insertions, 6 deletions

diff --git a/src/util.h b/src/util.h
index 2050604e54..a6b88206e9 100644
--- a/src/util.h
+++ b/src/util.h
@@ -404,13 +404,27 @@ bool SoftSetArg(const std::string& strArg, const std::string& strValue);
  */
 bool SoftSetBoolArg(const std::string& strArg, bool fValue);
 
+/**
+ * MWC RNG of George Marsaglia
+ * This is intended to be fast. It has a period of 2^59.3, though the
+ * least significant 16 bits only have a period of about 2^30.1.
+ *
+ * @return random value
+ */
+extern uint32_t insecure_rand_Rz;
+extern uint32_t insecure_rand_Rw;
+static inline uint32_t insecure_rand(void)
+{
+  insecure_rand_Rz=36969*(insecure_rand_Rz&65535)+(insecure_rand_Rz>>16);
+  insecure_rand_Rw=18000*(insecure_rand_Rw&65535)+(insecure_rand_Rw>>16);
+  return (insecure_rand_Rw<<16)+insecure_rand_Rz;
+}
 
-
-
-
-
-
-
+/**
+ * Seed insecure_rand using the random pool.
+ * @param Deterministic Use a determinstic seed
+ */
+void seed_insecure_rand(bool fDeterministic=false);
 
 /** Median filter over a stream of values.
  * Returns the median of the last N numbers