Random Number Function Vectorization

Compiler Methodology for Intel® MIC Architecture

Vectorization Essentials, Random Number Function Vectorization

The Intel Compiler version 13.0 supports random number auto- vectorization of the drand48 family of random number functions in C/C++ and RANF and Random_Number functions in Fortran. Vectorization is supported through the Intel Short Vector Math Library (SVML).

Supported C/C++ Functions:

double drand48(void);
double erand48(unsigned short xsubi[3]);
long int lrand48(void);
long int nrand48(unsigned short xsubi[3]);
long int mrand48(void);
long int jrand48(unsigned short xsubi[3]);

Simple Examples:

1. drand48 vectorization.

#include <stdlib.h>

#include <stdio.h>
#define ASIZE 1024

int main(int argc, char *argv[])
{
    int i;
    double rand_number[ASIZE] = {0};
    unsigned short seed[3] = {155,0,155};

    // Initialize Seed Value For Random Number
    seed48(&seed[0]);

    for (i = 0; i < ASIZE; i++){
        rand_number[i] = drand48();
    }

    // Sample Array Element
    printf("%f\n", rand_number[ASIZE-1]);
    return 0;
}

2. erand48 vectorization, seed value is passed as an argument.

#include <stdlib.h>

#include <stdio.h>
#define ASIZE 1024

int main(int argc,  char *argv[])
{
    int i;
    double rand_number [ASIZE] = {0};
    unsigned short seed[3] = {155,0,155};

    #pragma ivdep
    for (i = 0; i < ASIZE; i++){
        rand_number[i] = erand48(&seed[0]);
    }

    // Sample Array Element
    printf("%f\n", rand_number[ASIZE-1]);
    return 0;
}

3. lrand48 vectorization

#include <stdlib.h>
#include <stdio.h>
#define ASIZE 1024

int main(int argc, char *argv[])
{
    int i;
    long rand_number[ASIZE] = {0};
    unsigned short seed[3] = {155,0,155};

    // Initialize Value For Random Number
    seed48(&seed[0]);

    for (i = 0; i < ASIZE; i++){
        rand_number[i] = lrand48();
    }

    // Sample Array Element
    printf("%ld\n", rand_number[ASIZE-1]);
    return 0;
}

4. nrand48 vectorization, seed value id passed as an argument.

#include <stdlib.h>
#include <stdio.h>
#define ASIZE 1024

int main(int argc,  char *argv[])
{
    int i;
    long rand_number[ASIZE] = {0};
    unsigned short seed[3] = {155,0,155};

    #pragma ivdep
    for (i = 0; i < ASIZE; i++){
        rand_number[i] = nrand48(&seed[0]);
    }

    // Sample Array Element
    printf("%ld\n", rand_number[ASIZE-1]);
    return 0;
}

5. mrand48 vectorization.

#include <stdlib.h>

#include <stdio.h>
#define ASIZE 1024

int main(int argc,  char *argv[])
{
    int i;
    long rand_number[ASIZE] = {0};
    unsigned short seed[3] = {155,0,155};

    // Initialize Seed Value For Random Number
    seed48(&seed[0]);

    for (i = 0; i < ASIZE; i++){
        rand_number[i] = mrand48();
    }

    // Sample Array Element
    printf("%ld\n", rand_number[ASIZE-1]);
    return 0;
}

6. jrand48 vectorization, seed value is passed as an argument.

#include <stdlib.h>
#include <stdio.h>
#define ASIZE 1024

int main(int argc,  char *argv[])
{
    int i;
    long rand_number[ASIZE] = {0};
    unsigned short seed[3] = {155,0,155};

    #pragma ivdep
    for (i = 0; i < ASIZE; i++){
        rand_number[i] = jrand48(&seed[0]);
    }

    // Sample Array Element
    printf("%ld\n", rand_number[ASIZE-1]);
    return 0;
}

Fortran Support:

For Fortran we support:

RANF()

RANDOM_NUMBER() single precision

RANDOM_NUMBER() double precision

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