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.
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Inuyasha
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106
src/m_random.c
106
src/m_random.c
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@ -10,7 +10,7 @@
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// See the 'LICENSE' file for more details.
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//-----------------------------------------------------------------------------
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/// \file m_random.c
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/// \brief LCG PRNG originally created for XMOD
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/// \brief RNG for client effects and PRNG for game actions
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#include "doomdef.h"
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#include "doomtype.h"
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@ -42,7 +42,7 @@ UINT8 M_Random(void)
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*/
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INT32 M_SignedRandom(void)
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{
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return M_Random() - 128;
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return (rand() & 255) - 128;
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}
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/** Provides a random number in between 0 and the given number - 1.
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@ -80,12 +80,29 @@ static UINT32 randomseed = 0;
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static UINT32 initialseed = 0;
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/**
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* Provides a random byte and sets the seed appropriately.
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* The nature of this PRNG allows it to cycle through about two million numbers
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* before it finally starts repeating numeric sequences.
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* That's more than good enough for our purposes.
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* Provides a random fixed point number.
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* This is a variant of an xorshift PRNG; state fits in a 32 bit integer structure.
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*
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* \return A random byte, 0 to 255.
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* \return A random fixed point number from [0,1).
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*/
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ATTRINLINE static fixed_t FUNCINLINE __internal_prng__(void)
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{
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randomseed += 7069;
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randomseed ^= randomseed << 17;
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randomseed ^= randomseed >> 9;
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randomseed *= 373;
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randomseed ^= randomseed << 21;
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randomseed ^= randomseed >> 15;
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return (randomseed&((FRACUNIT-1)<<9))>>9;
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}
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/** Provides a random integer from 0 to 255.
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* Distribution is uniform.
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* If you're curious, (&0xFF00) >> 8 gives the same result
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* as a fixed point multiplication by 256.
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*
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* \return Random integer from [0, 255].
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* \sa __internal_prng__
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*/
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#ifndef DEBUGRANDOM
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UINT8 P_Random(void)
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@ -95,15 +112,14 @@ UINT8 P_RandomD(const char *rfile, INT32 rline)
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{
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CONS_Printf("P_Random() at: %sp %d\n", rfile, rline);
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#endif
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randomseed = (randomseed*746151647)+48205429;
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return (UINT8)((randomseed >> 17)&255);
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return (UINT8)((__internal_prng__()&0xFF00)>>8);
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}
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/** Provides a random number from -128 to 127.
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/** Provides a random integer from -128 to 127.
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* Distribution is uniform.
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*
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* \return Random number from -128 to 127.
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* \sa P_Random
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* \return Random integer from [-128, 127].
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* \sa __internal_prng__
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*/
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#ifndef DEBUGRANDOM
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INT32 P_SignedRandom(void)
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@ -113,15 +129,31 @@ INT32 P_SignedRandomD(const char *rfile, INT32 rline)
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{
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CONS_Printf("P_SignedRandom() at: %sp %d\n", rfile, rline);
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#endif
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return P_Random() - 128;
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return (INT32)((__internal_prng__()&0xFF00)>>8) - 128;
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}
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/** Provides a random number in between 0 and the given number - 1.
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* Distribution is uniform, also calls for two numbers for bigger output range.
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* Use for picking random elements from an array.
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/**
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* Provides a random fixed point number.
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* Literally a wrapper for the internal PRNG function.
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*
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* \return A random number, 0 to arg1-1.
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* \sa P_Random
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* \return A random fixed point number from [0,1).
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*/
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#ifndef DEBUGRANDOM
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fixed_t P_RandomFixed(void)
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{
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#else
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UINT8 P_RandomFixedD(const char *rfile, INT32 rline)
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{
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CONS_Printf("P_Random() at: %sp %d\n", rfile, rline);
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#endif
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return __internal_prng__();
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}
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/** Provides a random integer for picking random elements from an array.
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* Distribution is uniform.
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*
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* \return A random integer from [0,a).
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* \sa __internal_prng__
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*/
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#ifndef DEBUGRANDOM
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INT32 P_RandomKey(INT32 a)
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@ -131,16 +163,14 @@ INT32 P_RandomKeyD(const char *rfile, INT32 rline, INT32 a)
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{
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CONS_Printf("P_RandomKey() at: %sp %d\n", rfile, rline);
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#endif
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INT32 prandom = P_Random(); // note: forcing explicit function call order
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prandom |= P_Random() << 8; // (function call order is not strictly defined)
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return (INT32)((prandom/65536.0f)*a);
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return (INT32)((__internal_prng__() * a) >> FRACBITS);
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}
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/** Provides a random number in between a specific range.
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* Distribution is uniform, also calls for two numbers for bigger output range.
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/** Provides a random integer in a given range.
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* Distribution is uniform.
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*
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* \return A random number, arg1 to arg2.
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* \sa P_Random
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* \return A random integer from [a,b].P_Random
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* \sa __internal_prng__
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*/
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#ifndef DEBUGRANDOM
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INT32 P_RandomRange(INT32 a, INT32 b)
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@ -150,21 +180,27 @@ INT32 P_RandomRangeD(const char *rfile, INT32 rline, INT32 a, INT32 b)
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{
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CONS_Printf("P_RandomRange() at: %sp %d\n", rfile, rline);
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#endif
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INT32 prandom = P_Random(); // note: forcing explicit function call order
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prandom |= P_Random() << 8; // (function call order is not strictly defined)
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return (INT32)((prandom/65536.0f)*(b-a+1))+a;
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return (INT32)((__internal_prng__() * (b-a+1)) >> FRACBITS) + a;
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}
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/** Provides a random byte without saving what the seed would be.
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* Used just to debug the PRNG.
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// ----------------------
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// PRNG seeds & debugging
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// ----------------------
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/** Peeks to see what the next result from the PRNG will be.
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* Used for debugging.
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*
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* \return A 'random' byte, 0 to 255.
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* \sa P_Random
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* \return A 'random' fixed point number from [0,1).
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* \sa __internal_prng__
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*/
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UINT8 P_RandomPeek(void)
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fixed_t P_RandomPeek(void)
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{
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UINT32 r = (randomseed*746151647)+48205429;
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return (UINT8)((r >> 17)&255);
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UINT32 r = randomseed;
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fixed_t ret = __internal_prng__();
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randomseed = r;
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return ret;
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}
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/** Gets the current random seed. Used by netgame savegames.
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@ -20,8 +20,9 @@
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//#define DEBUGRANDOM
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// M_Random functions pull random numbers of various types that aren't network synced.
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// P_Random functions pulls random bytes from a LCG PRNG that is network synced.
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// P_Random functions pulls random bytes from a PRNG that is network synced.
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// RNG functions
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UINT8 M_Random(void);
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@ -31,21 +32,24 @@ INT32 M_RandomRange(INT32 a, INT32 b);
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// PRNG functions
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#ifdef DEBUGRANDOM
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#define P_Random() P_RandomD(__FILE__, __LINE__)
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#define P_SignedRandom() P_SignedRandomD(__FILE__, __LINE__)
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#define P_RandomKey(c) P_RandomKeyD(__FILE__, __LINE__, c)
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#define P_Random() P_RandomD(__FILE__, __LINE__)
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#define P_SignedRandom() P_SignedRandomD(__FILE__, __LINE__)
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#define P_RandomFixed() P_RandomFixedD(__FILE__, __LINE__)
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#define P_RandomKey(c) P_RandomKeyD(__FILE__, __LINE__, c)
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#define P_RandomRange(c, d) P_RandomRangeD(__FILE__, __LINE__, c, d)
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UINT8 P_RandomD(const char *rfile, INT32 rline);
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INT32 P_SignedRandomD(const char *rfile, INT32 rline);
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fixed_t P_RandomFixedD(const char *rfile, INT32 rline);
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INT32 P_RandomKeyD(const char *rfile, INT32 rline, INT32 a);
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INT32 P_RandomRangeD(const char *rfile, INT32 rline, INT32 a, INT32 b);
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#else
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UINT8 P_Random(void);
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INT32 P_SignedRandom(void);
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fixed_t P_RandomFixed(void);
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INT32 P_RandomKey(INT32 a);
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INT32 P_RandomRange(INT32 a, INT32 b);
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#endif
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UINT8 P_RandomPeek(void);
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fixed_t P_RandomPeek(void);
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// Working with the seed for PRNG
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#ifdef DEBUGRANDOM
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@ -592,9 +592,13 @@ static void ST_drawDebugInfo(void)
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if (cv_debug & DBG_RANDOMIZER) // randomizer testing
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{
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fixed_t peekres = P_RandomPeek();
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peekres *= 10000; // Change from fixed point
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peekres >>= FRACBITS; // to displayable decimal
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V_DrawRightAlignedString(320, height - 16, V_MONOSPACE, va("Init: %08x", P_GetInitSeed()));
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V_DrawRightAlignedString(320, height - 8, V_MONOSPACE, va("Seed: %08x", P_GetRandSeed()));
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V_DrawRightAlignedString(320, height, V_MONOSPACE, va("== : %8d", P_RandomPeek()));
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V_DrawRightAlignedString(320, height, V_MONOSPACE, va("== : .%04d", peekres));
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height -= 32;
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}
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