1 #include <petsc/private/randomimpl.h> 2 3 typedef struct { 4 unsigned short seed[3]; 5 unsigned short mult[3]; 6 unsigned short add; 7 } PetscRandom_Rander48; 8 9 #define RANDER48_SEED_0 (0x330e) 10 #define RANDER48_SEED_1 (0xabcd) 11 #define RANDER48_SEED_2 (0x1234) 12 #define RANDER48_MULT_0 (0xe66d) 13 #define RANDER48_MULT_1 (0xdeec) 14 #define RANDER48_MULT_2 (0x0005) 15 #define RANDER48_ADD (0x000b) 16 17 static double _dorander48(PetscRandom_Rander48 *r48) 18 { 19 unsigned long accu; 20 unsigned short temp[2]; 21 22 accu = (unsigned long)r48->mult[0] * (unsigned long)r48->seed[0] + (unsigned long)r48->add; 23 temp[0] = (unsigned short)accu; /* lower 16 bits */ 24 accu >>= sizeof(unsigned short) * 8; 25 accu += (unsigned long)r48->mult[0] * (unsigned long)r48->seed[1] + (unsigned long)r48->mult[1] * (unsigned long)r48->seed[0]; 26 temp[1] = (unsigned short)accu; /* middle 16 bits */ 27 accu >>= sizeof(unsigned short) * 8; 28 accu += (unsigned long)r48->mult[0] * r48->seed[2] + (unsigned long)r48->mult[1] * r48->seed[1] + (unsigned long)r48->mult[2] * r48->seed[0]; 29 r48->seed[0] = temp[0]; 30 r48->seed[1] = temp[1]; 31 r48->seed[2] = (unsigned short)accu; 32 return ldexp((double)r48->seed[0], -48) + ldexp((double)r48->seed[1], -32) + ldexp((double)r48->seed[2], -16); 33 } 34 35 static PetscErrorCode PetscRandomSeed_Rander48(PetscRandom r) 36 { 37 PetscRandom_Rander48 *r48 = (PetscRandom_Rander48 *)r->data; 38 39 PetscFunctionBegin; 40 r48->seed[0] = RANDER48_SEED_0; 41 r48->seed[1] = (unsigned short)r->seed; 42 r48->seed[2] = (unsigned short)(r->seed >> 16); 43 r48->mult[0] = RANDER48_MULT_0; 44 r48->mult[1] = RANDER48_MULT_1; 45 r48->mult[2] = RANDER48_MULT_2; 46 r48->add = RANDER48_ADD; 47 PetscFunctionReturn(PETSC_SUCCESS); 48 } 49 50 static PetscErrorCode PetscRandomGetValue_Rander48(PetscRandom r, PetscScalar *val) 51 { 52 PetscRandom_Rander48 *r48 = (PetscRandom_Rander48 *)r->data; 53 54 PetscFunctionBegin; 55 #if defined(PETSC_USE_COMPLEX) 56 if (r->iset) { 57 *val = PetscRealPart(r->low) + PetscImaginaryPart(r->low) * PETSC_i; 58 if (PetscRealPart(r->width)) *val += PetscRealPart(r->width) * _dorander48(r48); 59 if (PetscImaginaryPart(r->width)) *val += PetscImaginaryPart(r->width) * _dorander48(r48) * PETSC_i; 60 } else { 61 *val = _dorander48(r48) + _dorander48(r48) * PETSC_i; 62 } 63 #else 64 if (r->iset) *val = r->width * _dorander48(r48) + r->low; 65 else *val = _dorander48(r48); 66 #endif 67 PetscFunctionReturn(PETSC_SUCCESS); 68 } 69 70 static PetscErrorCode PetscRandomGetValueReal_Rander48(PetscRandom r, PetscReal *val) 71 { 72 PetscRandom_Rander48 *r48 = (PetscRandom_Rander48 *)r->data; 73 74 PetscFunctionBegin; 75 #if defined(PETSC_USE_COMPLEX) 76 if (r->iset) *val = PetscRealPart(r->width) * _dorander48(r48) + PetscRealPart(r->low); 77 else *val = _dorander48(r48); 78 #else 79 if (r->iset) *val = r->width * _dorander48(r48) + r->low; 80 else *val = _dorander48(r48); 81 #endif 82 PetscFunctionReturn(PETSC_SUCCESS); 83 } 84 85 static PetscErrorCode PetscRandomDestroy_Rander48(PetscRandom r) 86 { 87 PetscFunctionBegin; 88 PetscCall(PetscFree(r->data)); 89 PetscFunctionReturn(PETSC_SUCCESS); 90 } 91 92 static struct _PetscRandomOps PetscRandomOps_Values = { 93 PetscDesignatedInitializer(seed, PetscRandomSeed_Rander48), 94 PetscDesignatedInitializer(getvalue, PetscRandomGetValue_Rander48), 95 PetscDesignatedInitializer(getvaluereal, PetscRandomGetValueReal_Rander48), 96 PetscDesignatedInitializer(getvalues, NULL), 97 PetscDesignatedInitializer(getvaluesreal, NULL), 98 PetscDesignatedInitializer(destroy, PetscRandomDestroy_Rander48), 99 }; 100 101 /*MC 102 PETSCRANDER48 - simple portable reimplementation of basic Unix `drand48()` random number generator that should generate the 103 exact same random numbers on any system. 104 105 Options Database Key: 106 . -random_type <rand,rand48,rander48,sprng> - select the random number generator at runtime 107 108 Level: beginner 109 110 Notes: 111 This is the default random number generate provided by `PetscRandomCreate()` if you do not set a particular implementation. 112 113 Each `PetscRandom` object created with this type has its own seed and its own history, so multiple `PetscRandom` objects of this type 114 will not interfere with random numbers generated by other objects. Each PETSc object of this type will produce the exact same set of 115 random numbers so if you wish different `PetscRandom` objects of this type set different seeds for each one after you create them with 116 `PetscRandomSetSeed()` followed by `PetscRandomSeed()`. 117 118 .seealso: `PetscRandomCreate()`, `PetscRandomSetType()`, `PETSCRAND`, `PETSCRAND48`, `PETSCRANDER48`, `PETSCSPRNG`, `PetscRandomSetSeed()`, 119 `PetscRandomSeed()`, `PetscRandomSetFromOptions()` 120 M*/ 121 122 PETSC_EXTERN PetscErrorCode PetscRandomCreate_Rander48(PetscRandom r) 123 { 124 PetscRandom_Rander48 *r48; 125 126 PetscFunctionBegin; 127 PetscCall(PetscNew(&r48)); 128 /* r48 does not need to be initialized because PetscRandomSeed() is always called before use and sets the needed values */ 129 r->data = r48; 130 r->ops[0] = PetscRandomOps_Values; 131 PetscCall(PetscObjectChangeTypeName((PetscObject)r, PETSCRANDER48)); 132 PetscFunctionReturn(PETSC_SUCCESS); 133 } 134