Imported existing code

indra/llcommon/llrand.h

@@ -0,0 +1,133 @@
+/** 
+ * @file llrand.h
+ * @brief Information, functions, and typedefs for randomness.
+ *
+ * $LicenseInfo:firstyear=2000&license=viewergpl$
+ * 
+ * Copyright (c) 2000-2009, Linden Research, Inc.
+ * 
+ * Second Life Viewer Source Code
+ * The source code in this file ("Source Code") is provided by Linden Lab
+ * to you under the terms of the GNU General Public License, version 2.0
+ * ("GPL"), unless you have obtained a separate licensing agreement
+ * ("Other License"), formally executed by you and Linden Lab.  Terms of
+ * the GPL can be found in doc/GPL-license.txt in this distribution, or
+ * online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
+ * 
+ * There are special exceptions to the terms and conditions of the GPL as
+ * it is applied to this Source Code. View the full text of the exception
+ * in the file doc/FLOSS-exception.txt in this software distribution, or
+ * online at
+ * http://secondlifegrid.net/programs/open_source/licensing/flossexception
+ * 
+ * By copying, modifying or distributing this software, you acknowledge
+ * that you have read and understood your obligations described above,
+ * and agree to abide by those obligations.
+ * 
+ * ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
+ * WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
+ * COMPLETENESS OR PERFORMANCE.
+ * $/LicenseInfo$
+ */
+
+#ifndef LL_LLRAND_H
+#define LL_LLRAND_H
+
+#include <boost/random/lagged_fibonacci.hpp>
+#include <boost/random/mersenne_twister.hpp>
+
+/**
+ * Use the boost random number generators if you want a stateful
+ * random numbers. If you want more random numbers, use the
+ * c-functions since they will generate faster/better randomness
+ * across the process.
+ *
+ * I tested some of the boost random engines, and picked a good double
+ * generator and a good integer generator. I also took some timings
+ * for them on linux using gcc 3.3.5. The harness also did some other
+ * fairly trivial operations to try to limit compiler optimizations,
+ * so these numbers are only good for relative comparisons.
+ *
+ * usec/inter		algorithm
+ * 0.21				boost::minstd_rand0
+ * 0.039			boost:lagged_fibonacci19937
+ * 0.036			boost:lagged_fibonacci607
+ * 0.44				boost::hellekalek1995
+ * 0.44				boost::ecuyer1988
+ * 0.042			boost::rand48
+ * 0.043			boost::mt11213b
+ * 0.028			stdlib random() 
+ * 0.05				stdlib lrand48()
+ * 0.034			stdlib rand()
+ * 0.020			the old & lame LLRand
+ */
+
+/**
+ *@brief Generate a float from [0, RAND_MAX).
+ */
+S32 ll_rand();
+
+/**
+ *@brief Generate a float from [0, val) or (val, 0].
+ */
+S32 ll_rand(S32 val);
+
+/**
+ *@brief Generate a float from [0, 1.0).
+ */
+F32 ll_frand();
+
+/**
+ *@brief Generate a float from [0, val) or (val, 0].
+ */
+F32 ll_frand(F32 val);
+
+/**
+ *@brief Generate a double from [0, 1.0).
+ */
+F64 ll_drand();
+
+/**
+ *@brief Generate a double from [0, val) or (val, 0].
+ */
+F64 ll_drand(F64 val);
+
+/**
+ * @brief typedefs for good boost lagged fibonacci.
+ * @see boost::lagged_fibonacci
+ *
+ * These generators will quickly generate doubles. Note the memory
+ * requirements, because they are somewhat high. I chose the smallest
+ * one, and one comparable in speed but higher periodicity without
+ * outrageous memory requirements.
+ * To use:
+ *  LLRandLagFib607 foo((U32)time(NULL));
+ *  double bar = foo();
+ */
+
+typedef boost::lagged_fibonacci607 LLRandLagFib607;
+/**< 
+ * lengh of cycle: 2^32,000
+ * memory: 607*sizeof(double) (about 5K)
+ */
+
+typedef boost::lagged_fibonacci2281 LLRandLagFib2281;
+/**< 
+ * lengh of cycle: 2^120,000
+ * memory: 2281*sizeof(double) (about 17K)
+ */
+
+/**
+ * @breif typedefs for a good boost mersenne twister implementation.
+ * @see boost::mersenne_twister
+ *
+ * This fairly quickly generates U32 values
+ * To use:
+ *  LLRandMT19937 foo((U32)time(NULL));
+ *  U32 bar = foo();
+ *
+ * lengh of cycle: 2^19,937-1
+ * memory: about 2496 bytes
+ */
+typedef boost::mt11213b LLRandMT19937;
+#endif