Actual source code: rander48.c
petsc-3.10.5 2019-03-28
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      1: #include <../src/sys/classes/random/randomimpl.h>

      3: typedef struct {
      4:   unsigned short seed[3];
      5:   unsigned short mult[3];
      6:   unsigned short add;
      7: } PetscRandom_Rander48;

      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)

     17: static double _dorander48(PetscRandom_Rander48 *r48)
     18: {
     19:   unsigned long accu;
     20:   unsigned short temp[2];

     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    += r48->mult[0] * r48->seed[2] + r48->mult[1] * r48->seed[1] + 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: }

     35: static PetscErrorCode  PetscRandomSeed_Rander48(PetscRandom r)
     36: {
     37:   PetscRandom_Rander48 *r48 = (PetscRandom_Rander48*)r->data;

     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:   return(0);
     48: }

     50: static PetscErrorCode  PetscRandomGetValue_Rander48(PetscRandom r, PetscScalar *val)
     51: {
     52:   PetscRandom_Rander48 *r48 = (PetscRandom_Rander48*)r->data;

     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)) {
     59:       *val += PetscRealPart(r->width)* _dorander48(r48);
     60:     }
     61:     if (PetscImaginaryPart(r->width)) {
     62:       *val += PetscImaginaryPart(r->width)* _dorander48(r48) * PETSC_i;
     63:     }
     64:   } else {
     65:     *val = _dorander48(r48) +  _dorander48(r48)*PETSC_i;
     66:   }
     67: #else
     68:   if (r->iset) *val = r->width * _dorander48(r48) + r->low;
     69:   else         *val = _dorander48(r48);
     70: #endif
     71:   return(0);
     72: }

     74: static PetscErrorCode  PetscRandomGetValueReal_Rander48(PetscRandom r, PetscReal *val)
     75: {
     76:   PetscRandom_Rander48 *r48 = (PetscRandom_Rander48*)r->data;

     79: #if defined(PETSC_USE_COMPLEX)
     80:   if (r->iset) *val = PetscRealPart(r->width)*_dorander48(r48) + PetscRealPart(r->low);
     81:   else         *val = _dorander48(r48);
     82: #else
     83:   if (r->iset) *val = r->width * _dorander48(r48) + r->low;
     84:   else         *val = _dorander48(r48);
     85: #endif
     86:   return(0);
     87: }

     89: static PetscErrorCode  PetscRandomDestroy_Rander48(PetscRandom r)
     90: {

     94:   PetscFree(r->data);
     95:   return(0);
     96: }

     98: static struct _PetscRandomOps PetscRandomOps_Values = {
     99:   /* 0 */
    100:   PetscRandomSeed_Rander48,
    101:   PetscRandomGetValue_Rander48,
    102:   PetscRandomGetValueReal_Rander48,
    103:   PetscRandomDestroy_Rander48,
    104:   /* 5 */
    105:   0
    106: };

    108: /*MC
    109:    PETSCRANDER48 - simple portable reimplementation of basic Unix drand48() random number generator that should generate the
    110:         exact same random numbers on any system.

    112:    Options Database Keys:
    113: . -random_type <rand,rand48,rander48,sprng>

    115:   Notes:
    116:     This is the default random number generate provided by PetscRandomCreate() if you do not set a particular implementation.

    118:   Each PetscRandom object created with this type has its own seed and its own history, so multiple PetscRandom objects of this type
    119:   will not interfer with random numbers generated by other objects. Each PETSc object of this type will produce the exact same set of
    120:   random numbers so if you wish different PetscObjects of this type set different seeds for each one after you create them with
    121:   PetscRandomSetSeed() followed by PetscRandomSeed().

    123:   Level: beginner

    125: .seealso: RandomCreate(), RandomSetType(), PETSCRAND, PETSCRAND48, PETSCRANDER48, PETSCSPRNG, PetscRandomSetSeed(), PetscRandomSeed()
    126: M*/

    128: PETSC_EXTERN PetscErrorCode PetscRandomCreate_Rander48(PetscRandom r)
    129: {
    130:   PetscErrorCode       ierr;
    131:   PetscRandom_Rander48 *r48;

    134:   PetscNewLog(r,&r48);
    135:   /* r48 does not need to be initialized because PetscRandomSeed() is always called before use and sets the needed values */
    136:   r->data = r48;
    137:   PetscMemcpy(r->ops, &PetscRandomOps_Values, sizeof(PetscRandomOps_Values));
    138:   PetscObjectChangeTypeName((PetscObject) r, PETSCRANDER48);
    139:   return(0);
    140: }