//Marsaglia's MWC (multiply with carry) algorithm
static uint32_t m_z = 333, m_w = 888;  // any seeds not null
uint32_t GetUint()
{
    m_z = 36969 * (m_z & 65535) + (m_z >> 16);
    m_w = 18000 * (m_w & 65535) + (m_w >> 16);
    return (m_z << 16) + m_w;
}

double GetUniform()
{
    // 0 <= u < 2^32
    uint32_t u = GetUint();
    // The magic number below is 1/(2^32 + 2).
    // The result is strictly between 0 and 1.
    return (u + 1.0) * 2.328306435454494e-10;
}

GetUint:
  mov eax, DWORD PTR m_z
  movzx edx, ax
  imul edx, edx, 36969
  shr eax, 16
  add eax, edx
  mov DWORD PTR m_z, eax
  mov edx, DWORD PTR m_w
  movzx ecx, dx
  imul ecx, ecx, 18000
  shr edx, 16
  add edx, ecx
  mov DWORD PTR m_w, edx
  sal eax, 16
  add eax, edx
  ret
m_w:
  .long 888
m_z:
  .long 333

/*
   32-bits Random number generator U[0,1): lfsr113
   Author: Pierre L'Ecuyer,
   Source: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps
   ---------------------------------------------------------
*/

#include "lfsr113.h"
#include <stdint.h>


/**** VERY IMPORTANT **** :
  The initial seeds z1, z2, z3, z4  MUST be larger than
  1, 7, 15, and 127 respectively.
****/

#define SEED 987654321

static uint32_t z1 = SEED, z2 = SEED, z3 = SEED, z4 = SEED;


double lfsr113 (void)
{
   uint32_t b;
   b  = ((z1 << 6) ^ z1) >> 13;
   z1 = ((z1 & 4294967294U) << 18) ^ b;
   b  = ((z2 << 2) ^ z2) >> 27;
   z2 = ((z2 & 4294967288U) << 2) ^ b;
   b  = ((z3 << 13) ^ z3) >> 21;
   z3 = ((z3 & 4294967280U) << 7) ^ b;
   b  = ((z4 << 3) ^ z4) >> 12;
   z4 = ((z4 & 4294967168U) << 13) ^ b;
   return (z1 ^ z2 ^ z3 ^ z4) * 2.3283064365386963e-10;
}

.Data
RandSeed Dword 0
.Code
; ******************************************************************************
; Initialize the random-number generator
Randomize Proc
  rdtsc
  mov RandSeed, eax
  ret
Randomize EndP
; ******************************************************************************
; Produce random values in a given range [MinValue..MaxValue]
Random Proc MinValue:Dword, MaxValue:Dword
  mov eax, 134775813
  mul RandSeed
  inc eax
  mov RandSeed, eax
  mov edx, MaxValue
  sub edx, MinValue
  inc edx
  mul edx
  mov eax, edx
  add eax, MinValue
  ret
Random EndP

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