1 | /* Copyright (c) 2001, Stanford University
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2 | * All rights reserved
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3 | *
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4 | * See the file LICENSE.txt for information on redistributing this software.
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5 | */
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6 |
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7 | #include "cr_rand.h"
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8 |
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9 | #ifdef WINDOWS
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10 | #define WIN32_LEAN_AND_MEAN
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11 | #include <windows.h>
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12 | #else
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13 | #include <sys/time.h>
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14 | #endif
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15 |
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16 |
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17 | /* Period parameters */
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18 | #define N 624
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19 | #define M 397
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20 | #define MATRIX_A 0x9908b0df /* constant vector a */
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21 | #define UPPER_MASK 0x80000000 /* most significant w-r bits */
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22 | #define LOWER_MASK 0x7fffffff /* least significant r bits */
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23 |
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24 | /* Tempering parameters */
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25 | #define TEMPERING_MASK_B 0x9d2c5680
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26 | #define TEMPERING_MASK_C 0xefc60000
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27 | #define TEMPERING_SHIFT_U(y) (y >> 11)
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28 | #define TEMPERING_SHIFT_S(y) (y << 7)
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29 | #define TEMPERING_SHIFT_T(y) (y << 15)
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30 | #define TEMPERING_SHIFT_L(y) (y >> 18)
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31 |
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32 | static unsigned long mt[N]; /* the array for the state vector */
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33 | static int mti=N+1; /* mti==N+1 means mt[N] is not initialized */
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34 |
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35 | void crRandSeed(unsigned long seed)
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36 | {
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37 | /* setting initial seeds to mt[N] using the generator Line 25 of Table 1
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38 | in [KNUTH 1981, The Art of Computer Programming Vol. 2 (2nd Ed.),
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39 | pp102
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40 | */
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41 | if (seed == 0)
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42 | seed = 4357; /* pick default seed if seed=0 (Guy Zadickario) */
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43 | mt[0]= seed & 0xffffffff;
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44 | for (mti=1; mti<N; mti++)
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45 | mt[mti] = (69069 * mt[mti-1]) & 0xffffffff;
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46 | }
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47 |
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48 |
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49 | /*
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50 | * Seed the generator based on time of day or a system counter.
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51 | */
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52 | void crRandAutoSeed(void)
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53 | {
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54 | #if defined(WINDOWS)
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55 | LARGE_INTEGER counter;
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56 | QueryPerformanceCounter( &counter );
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57 | crRandSeed((unsigned long) counter.QuadPart);
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58 | #else
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59 | struct timeval timeofday;
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60 | gettimeofday( &timeofday, 0 );
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61 | crRandSeed((unsigned long) timeofday.tv_usec);
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62 | #endif
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63 | }
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64 |
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65 |
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66 | static double genrand( void )
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67 | {
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68 | unsigned long y;
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69 | static unsigned long mag01[2]={0x0, MATRIX_A};
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70 | /* mag01[x] = x * MATRIX_A for x=0,1 */
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71 |
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72 | if (mti >= N) { /* generate N words at one time */
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73 | int kk;
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74 | if (mti == N+1) /* if sgenrand() has not been called, */
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75 | crRandSeed(4357); /* a default initial seed is used */
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76 |
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77 | for (kk=0;kk<N-M;kk++) {
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78 | y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
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79 | mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
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80 | }
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81 | for (;kk<N-1;kk++) {
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82 | y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
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83 | mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
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84 | }
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85 | y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
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86 | mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
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87 | mti = 0;
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88 | }
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89 |
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90 | y = mt[mti++];
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91 | y ^= TEMPERING_SHIFT_U(y);
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92 | y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
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93 | y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
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94 | y ^= TEMPERING_SHIFT_L(y);
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95 |
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96 | return ( (double)y / (unsigned long)0xffffffff ); /* reals */
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97 | /* return y; */ /* for integer generation */
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98 | }
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99 |
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100 | float crRandFloat(float min, float max)
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101 | {
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102 | double t = genrand();
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103 | return (float) (t*min + (1-t)*max);
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104 | }
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105 |
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106 | /* return a random integer in [min, max] (inclusive). */
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107 | int crRandInt(int min, int max)
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108 | {
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109 | double t = genrand();
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110 | return min + (int) (t * (max - min + 1));
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111 | }
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