rocm-systems/examples/openmp/common/c_randdp.cpp

/*
MIT License

Copyright (c) 2021 Parallel Applications Modelling Group - GMAP
    GMAP website: https://gmap.pucrs.br

    Pontifical Catholic University of Rio Grande do Sul (PUCRS)
    Av. Ipiranga, 6681, Porto Alegre - Brazil, 90619-900

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

------------------------------------------------------------------------------

The original NPB 3.4.1 version was written in Fortran and belongs to:
    http://www.nas.nasa.gov/Software/NPB/

------------------------------------------------------------------------------

The serial C++ version is a translation of the original NPB 3.4.1
Serial C++ version: https://github.com/GMAP/NPB-CPP/tree/master/NPB-SER

Authors of the C++ code:
    Dalvan Griebler <dalvangriebler@gmail.com>
    Gabriell Araujo <hexenoften@gmail.com>
    Júnior Löff <loffjh@gmail.com>
*/

#if defined(USE_POW)
#    define r23 pow(0.5, 23.0)
#    define r46 (r23 * r23)
#    define t23 pow(2.0, 23.0)
#    define t46 (t23 * t23)
#else
#    define r23                                                                          \
        (0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 *   \
         0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5 * 0.5)
#    define r46 (r23 * r23)
#    define t23                                                                          \
        (2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 *   \
         2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0 * 2.0)
#    define t46 (t23 * t23)
#endif

/*
 * ---------------------------------------------------------------------
 *
 * this routine returns a uniform pseudorandom double precision number in the
 * range (0, 1) by using the linear congruential generator
 *
 * x_{k+1} = a x_k  (mod 2^46)
 *
 * where 0 < x_k < 2^46 and 0 < a < 2^46. this scheme generates 2^44 numbers
 * before repeating. the argument A is the same as 'a' in the above formula,
 * and X is the same as x_0.  A and X must be odd double precision integers
 * in the range (1, 2^46). the returned value RANDLC is normalized to be
 * between 0 and 1, i.e. RANDLC = 2^(-46) * x_1.  X is updated to contain
 * the new seed x_1, so that subsequent calls to RANDLC using the same
 * arguments will generate a continuous sequence.
 *
 * this routine should produce the same results on any computer with at least
 * 48 mantissa bits in double precision floating point data.  On 64 bit
 * systems, double precision should be disabled.
 *
 * David H. Bailey, October 26, 1990
 *
 * ---------------------------------------------------------------------
 */
double
randlc(double* x, double a)
{
    double t1, t2, t3, t4, a1, a2, x1, x2, z;

    /*
     * ---------------------------------------------------------------------
     * break A into two parts such that A = 2^23 * A1 + A2.
     * ---------------------------------------------------------------------
     */
    t1 = r23 * a;
    a1 = (int) t1;
    a2 = a - t23 * a1;

    /*
     * ---------------------------------------------------------------------
     * break X into two parts such that X = 2^23 * X1 + X2, compute
     * Z = A1 * X2 + A2 * X1  (mod 2^23), and then
     * X = 2^23 * Z + A2 * X2  (mod 2^46).
     * ---------------------------------------------------------------------
     */
    t1   = r23 * (*x);
    x1   = (int) t1;
    x2   = (*x) - t23 * x1;
    t1   = a1 * x2 + a2 * x1;
    t2   = (int) (r23 * t1);
    z    = t1 - t23 * t2;
    t3   = t23 * z + a2 * x2;
    t4   = (int) (r46 * t3);
    (*x) = t3 - t46 * t4;

    return (r46 * (*x));
}

/*
 * ---------------------------------------------------------------------
 *
 * this routine generates N uniform pseudorandom double precision numbers in
 * the range (0, 1) by using the linear congruential generator
 *
 * x_{k+1} = a x_k  (mod 2^46)
 *
 * where 0 < x_k < 2^46 and 0 < a < 2^46. this scheme generates 2^44 numbers
 * before repeating. the argument A is the same as 'a' in the above formula,
 * and X is the same as x_0. A and X must be odd double precision integers
 * in the range (1, 2^46). the N results are placed in Y and are normalized
 * to be between 0 and 1. X is updated to contain the new seed, so that
 * subsequent calls to VRANLC using the same arguments will generate a
 * continuous sequence.  if N is zero, only initialization is performed, and
 * the variables X, A and Y are ignored.
 *
 * this routine is the standard version designed for scalar or RISC systems.
 * however, it should produce the same results on any single processor
 * computer with at least 48 mantissa bits in double precision floating point
 * data. on 64 bit systems, double precision should be disabled.
 *
 * ---------------------------------------------------------------------
 */
void
vranlc(int n, double* x_seed, double a, double y[])
{
    int    i;
    double x, t1, t2, t3, t4, a1, a2, x1, x2, z;

    /*
     * ---------------------------------------------------------------------
     * break A into two parts such that A = 2^23 * A1 + A2.
     * ---------------------------------------------------------------------
     */
    t1 = r23 * a;
    a1 = (int) t1;
    a2 = a - t23 * a1;
    x  = *x_seed;

    /*
     * ---------------------------------------------------------------------
     * generate N results. this loop is not vectorizable.
     * ---------------------------------------------------------------------
     */
    for(i = 0; i < n; i++)
    {
        /*
         * ---------------------------------------------------------------------
         * break X into two parts such that X = 2^23 * X1 + X2, compute
         * Z = A1 * X2 + A2 * X1  (mod 2^23), and then
         * X = 2^23 * Z + A2 * X2  (mod 2^46).
         * ---------------------------------------------------------------------
         */
        t1   = r23 * x;
        x1   = (int) t1;
        x2   = x - t23 * x1;
        t1   = a1 * x2 + a2 * x1;
        t2   = (int) (r23 * t1);
        z    = t1 - t23 * t2;
        t3   = t23 * z + a2 * x2;
        t4   = (int) (r46 * t3);
        x    = t3 - t46 * t4;
        y[i] = r46 * x;
    }
    *x_seed = x;
}