Torque3D/Engine/source/math/mRandom.cpp

//-----------------------------------------------------------------------------
// Copyright (c) 2012 GarageGames, LLC
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
//-----------------------------------------------------------------------------

#include "platform/platform.h"
#include "math/mRandom.h"
#include "core/util/journal/journal.h"

MRandomLCG gRandGen;
U32 gRandGenSeed = 1376312589;

void MRandomLCG::setGlobalRandSeed(U32 seed)
{
	if (Journal::IsPlaying())
		Journal::Read(&gRandGenSeed);
	else
	{
		gRandGenSeed = seed;
		if (Journal::IsRecording())
			Journal::Write(gRandGenSeed);
	}

	//now actually set the seed
	gRandGen.setSeed(gRandGenSeed);
}

static U32 msSeed = 1376312589;

inline U32 generateSeed()
{
   // A very, VERY crude LCG but good enough to generate
   // a nice range of seed values
   msSeed = (msSeed * 0x015a4e35L) + 1;
   msSeed = (msSeed>>16)&0x7fff;
   return (msSeed);
}

//--------------------------------------
void MRandomGenerator::setSeed()
{
   setSeed(generateSeed());
}


//--------------------------------------
const S32 MRandomLCG::msQuotient  = S32_MAX / 16807L;
const S32 MRandomLCG::msRemainder = S32_MAX % 16807L;


//--------------------------------------
MRandomLCG::MRandomLCG()
{
   setSeed(generateSeed());
}

MRandomLCG::MRandomLCG(S32 s)
{
   setSeed(s);
}


//--------------------------------------
void MRandomLCG::setSeed(S32 s)
{
   mSeed = s;
}


//--------------------------------------
U32 MRandomLCG::randI()
{
   if ( mSeed <= msQuotient )
      mSeed = (mSeed * 16807) % S32_MAX;
   else
   {
      S32 high_part = mSeed / msQuotient;
      S32 low_part  = mSeed % msQuotient;

      S32 test = (16807 * low_part) - (msRemainder * high_part);

      if ( test > 0 )
         mSeed = test;
      else
         mSeed = test + S32_MAX;

   }
   return mSeed;
}



//--------------------------------------
MRandomR250::MRandomR250()
{
   setSeed(generateSeed());
}

MRandomR250::MRandomR250(S32 s)
{
   setSeed(s);
}


//--------------------------------------
void MRandomR250::setSeed(S32 s)
{
   mSeed = s;
   MRandomLCG lcg( s );
   mIndex = 0;

   S32 j;
   for (j = 0; j < 250; j++)        // fill r250 buffer with bit values
      mBuffer[j] = lcg.randI();

   for (j = 0; j < 250; j++)        // set some MSBs to 1
      if ( lcg.randI() > 0x40000000L )
         mBuffer[j] |= 0x80000000L;


   U32 msb  = 0x80000000;           // turn on diagonal bit
   U32 mask = 0xffffffff;           // turn off the leftmost bits

   for (j = 0; j < 32; j++)
   {
      S32 k = 7 * j + 3;            // select a word to operate on
      mBuffer[k] &= mask;           // turn off bits left of the diagonal
      mBuffer[k] |= msb;            // turn on the diagonal bit
      mask >>= 1;
      msb  >>= 1;
   }
}


//--------------------------------------
U32 MRandomR250::randI()
{
   S32 j;

   // wrap pointer around
   if ( mIndex >= 147 ) j = mIndex - 147;
   else                 j = mIndex + 103;

   U32 new_rand = mBuffer[ mIndex ] ^ mBuffer[ j ];
   mBuffer[ mIndex ] = new_rand;

   // increment pointer for next time
   if ( mIndex >= 249 ) mIndex = 0;
   else                 mIndex++;

   return new_rand >> 1;
}