Commit ce2c2de5 by Inuyasha

P_Random now using a variant of xorshift

This actually passes most diehard tests, as opposed to the old RNG. It's also similarly fast. Internally the PRNG generates a fixed point number from [0,1) now, which makes P_RandomKey and P_RandomRange much easier to calculate. P_Random is just a simple shift, as well. Also, the lack of floating point math in P_RandomKey and P_RandomRange now is probably for the best.
parent 83e9eb6d
......@@ -10,7 +10,7 @@
// See the 'LICENSE' file for more details.
//-----------------------------------------------------------------------------
/// \file m_random.c
/// \brief LCG PRNG originally created for XMOD
/// \brief RNG for client effects and PRNG for game actions
#include "doomdef.h"
#include "doomtype.h"
......@@ -42,7 +42,7 @@ UINT8 M_Random(void)
*/
INT32 M_SignedRandom(void)
{
return M_Random() - 128;
return (rand() & 255) - 128;
}
/** Provides a random number in between 0 and the given number - 1.
......@@ -80,12 +80,29 @@ static UINT32 randomseed = 0;
static UINT32 initialseed = 0;
/**
* Provides a random byte and sets the seed appropriately.
* The nature of this PRNG allows it to cycle through about two million numbers
* before it finally starts repeating numeric sequences.
* That's more than good enough for our purposes.
* Provides a random fixed point number.
* This is a variant of an xorshift PRNG; state fits in a 32 bit integer structure.
*
* \return A random byte, 0 to 255.
* \return A random fixed point number from [0,1).
*/
ATTRINLINE static fixed_t FUNCINLINE __internal_prng__(void)
{
randomseed += 7069;
randomseed ^= randomseed << 17;
randomseed ^= randomseed >> 9;
randomseed *= 373;
randomseed ^= randomseed << 21;
randomseed ^= randomseed >> 15;
return (randomseed&((FRACUNIT-1)<<9))>>9;
}
/** Provides a random integer from 0 to 255.
* Distribution is uniform.
* If you're curious, (&0xFF00) >> 8 gives the same result
* as a fixed point multiplication by 256.
*
* \return Random integer from [0, 255].
* \sa __internal_prng__
*/
#ifndef DEBUGRANDOM
UINT8 P_Random(void)
......@@ -95,15 +112,14 @@ UINT8 P_RandomD(const char *rfile, INT32 rline)
{
CONS_Printf("P_Random() at: %sp %d\n", rfile, rline);
#endif
randomseed = (randomseed*746151647)+48205429;
return (UINT8)((randomseed >> 17)&255);
return (UINT8)((__internal_prng__()&0xFF00)>>8);
}
/** Provides a random number from -128 to 127.
/** Provides a random integer from -128 to 127.
* Distribution is uniform.
*
* \return Random number from -128 to 127.
* \sa P_Random
* \return Random integer from [-128, 127].
* \sa __internal_prng__
*/
#ifndef DEBUGRANDOM
INT32 P_SignedRandom(void)
......@@ -113,15 +129,31 @@ INT32 P_SignedRandomD(const char *rfile, INT32 rline)
{
CONS_Printf("P_SignedRandom() at: %sp %d\n", rfile, rline);
#endif
return P_Random() - 128;
return (INT32)((__internal_prng__()&0xFF00)>>8) - 128;
}
/** Provides a random number in between 0 and the given number - 1.
* Distribution is uniform, also calls for two numbers for bigger output range.
* Use for picking random elements from an array.
/**
* Provides a random fixed point number.
* Literally a wrapper for the internal PRNG function.
*
* \return A random number, 0 to arg1-1.
* \sa P_Random
* \return A random fixed point number from [0,1).
*/
#ifndef DEBUGRANDOM
fixed_t P_RandomFixed(void)
{
#else
UINT8 P_RandomFixedD(const char *rfile, INT32 rline)
{
CONS_Printf("P_Random() at: %sp %d\n", rfile, rline);
#endif
return __internal_prng__();
}
/** Provides a random integer for picking random elements from an array.
* Distribution is uniform.
*
* \return A random integer from [0,a).
* \sa __internal_prng__
*/
#ifndef DEBUGRANDOM
INT32 P_RandomKey(INT32 a)
......@@ -131,16 +163,14 @@ INT32 P_RandomKeyD(const char *rfile, INT32 rline, INT32 a)
{
CONS_Printf("P_RandomKey() at: %sp %d\n", rfile, rline);
#endif
INT32 prandom = P_Random(); // note: forcing explicit function call order
prandom |= P_Random() << 8; // (function call order is not strictly defined)
return (INT32)((prandom/65536.0f)*a);
return (INT32)((__internal_prng__() * a) >> FRACBITS);
}
/** Provides a random number in between a specific range.
* Distribution is uniform, also calls for two numbers for bigger output range.
/** Provides a random integer in a given range.
* Distribution is uniform.
*
* \return A random number, arg1 to arg2.
* \sa P_Random
* \return A random integer from [a,b].P_Random
* \sa __internal_prng__
*/
#ifndef DEBUGRANDOM
INT32 P_RandomRange(INT32 a, INT32 b)
......@@ -150,21 +180,27 @@ INT32 P_RandomRangeD(const char *rfile, INT32 rline, INT32 a, INT32 b)
{
CONS_Printf("P_RandomRange() at: %sp %d\n", rfile, rline);
#endif
INT32 prandom = P_Random(); // note: forcing explicit function call order
prandom |= P_Random() << 8; // (function call order is not strictly defined)
return (INT32)((prandom/65536.0f)*(b-a+1))+a;
return (INT32)((__internal_prng__() * (b-a+1)) >> FRACBITS) + a;
}
/** Provides a random byte without saving what the seed would be.
* Used just to debug the PRNG.
// ----------------------
// PRNG seeds & debugging
// ----------------------
/** Peeks to see what the next result from the PRNG will be.
* Used for debugging.
*
* \return A 'random' byte, 0 to 255.
* \sa P_Random
* \return A 'random' fixed point number from [0,1).
* \sa __internal_prng__
*/
UINT8 P_RandomPeek(void)
fixed_t P_RandomPeek(void)
{
UINT32 r = (randomseed*746151647)+48205429;
return (UINT8)((r >> 17)&255);
UINT32 r = randomseed;
fixed_t ret = __internal_prng__();
randomseed = r;
return ret;
}
/** Gets the current random seed. Used by netgame savegames.
......
......@@ -20,8 +20,9 @@
//#define DEBUGRANDOM
// M_Random functions pull random numbers of various types that aren't network synced.
// P_Random functions pulls random bytes from a LCG PRNG that is network synced.
// P_Random functions pulls random bytes from a PRNG that is network synced.
// RNG functions
UINT8 M_Random(void);
......@@ -31,21 +32,24 @@ INT32 M_RandomRange(INT32 a, INT32 b);
// PRNG functions
#ifdef DEBUGRANDOM
#define P_Random() P_RandomD(__FILE__, __LINE__)
#define P_SignedRandom() P_SignedRandomD(__FILE__, __LINE__)
#define P_RandomKey(c) P_RandomKeyD(__FILE__, __LINE__, c)
#define P_Random() P_RandomD(__FILE__, __LINE__)
#define P_SignedRandom() P_SignedRandomD(__FILE__, __LINE__)
#define P_RandomFixed() P_RandomFixedD(__FILE__, __LINE__)
#define P_RandomKey(c) P_RandomKeyD(__FILE__, __LINE__, c)
#define P_RandomRange(c, d) P_RandomRangeD(__FILE__, __LINE__, c, d)
UINT8 P_RandomD(const char *rfile, INT32 rline);
INT32 P_SignedRandomD(const char *rfile, INT32 rline);
fixed_t P_RandomFixedD(const char *rfile, INT32 rline);
INT32 P_RandomKeyD(const char *rfile, INT32 rline, INT32 a);
INT32 P_RandomRangeD(const char *rfile, INT32 rline, INT32 a, INT32 b);
#else
UINT8 P_Random(void);
INT32 P_SignedRandom(void);
fixed_t P_RandomFixed(void);
INT32 P_RandomKey(INT32 a);
INT32 P_RandomRange(INT32 a, INT32 b);
#endif
UINT8 P_RandomPeek(void);
fixed_t P_RandomPeek(void);
// Working with the seed for PRNG
#ifdef DEBUGRANDOM
......
......@@ -592,9 +592,13 @@ static void ST_drawDebugInfo(void)
if (cv_debug & DBG_RANDOMIZER) // randomizer testing
{
fixed_t peekres = P_RandomPeek();
peekres *= 10000; // Change from fixed point
peekres >>= FRACBITS; // to displayable decimal
V_DrawRightAlignedString(320, height - 16, V_MONOSPACE, va("Init: %08x", P_GetInitSeed()));
V_DrawRightAlignedString(320, height - 8, V_MONOSPACE, va("Seed: %08x", P_GetRandSeed()));
V_DrawRightAlignedString(320, height, V_MONOSPACE, va("== : %8d", P_RandomPeek()));
V_DrawRightAlignedString(320, height, V_MONOSPACE, va("== : .%04d", peekres));
height -= 32;
}
......
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