scoprand.cpp

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#include <../../nrnconf.h>
#include <stdlib.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
 
/* this was removed from the scopmath library since there could be
multiple copies of the static value below. One in neuron.exe and the
other in nrnmech.dll.
*/
 
/******************************************************************************
 *
 * File: random.cpp
 *
 * Copyright (c) 1984, 1985, 1986, 1987, 1988, 1989, 1990
 *   Duke University
 *
 ******************************************************************************/
 
#include <math.h>
#include "oc_mcran4.hpp"
#include "mcran4.h"
#include "scoplib.h"
static uint32_t value = 1;
 
/*-----------------------------------------------------------------------------
 *
 *  SCOP_RANDOM()
 *
 *  Selects a random number from the uniform distribution on
 *  the interval [0,1].  A seed number can be specified by a
 *  call to the function set_seed(seed).  Otherwise, a seed
 *  of 1 will be used.
 *
 *  Calling sequence:
 *  scop_random()
 *
 *  Arguments:
 *  none for random; for set_seed
 *  Input:  seed, int   value of the seed
 *
 *  Output: argument unchanged
 *
 *
 *  Returns:
 *  Double precision value of the random number
 *
 *  Functions called:
 *  none
 *
 *  Files accessed:
 *  none
 *
 *--------------------------------------------------------------------------- */
 
double scop_random(void) {
    if (use_mcran4()) {
        /*perhaps 4 times slower but much higher quality*/
        return mcell_ran4a(&value);
    } else {
        uint32_t a = 2147437301, c = 453816981,
                 /* m = 2^32 - 1, the largest long int value that can be represented */
            /*m = 0xFFFFFFFF;*/ /* limited to 32 bit integers*/
            m = ~0;
        value = a * value + c;
        return (fabs((double) value / (double) m));
    }
}
 
/*-----------------------------------------------------------------------------
 *
 *  SET_SEED()
 *
 *  Set random number seed
 *
 *  Calling sequence:
 *  set_seed(seed)
 *
 *  Arguments:
 *  seed - integer random number seed
 *
 *  Returns:
 *  nothing
 *
 *  Functions called:
 *  none
 *
 *  Files accessed:
 *  none
 *
 */
 
void set_seed(double seed) {
    value = (uint32_t) seed;
}