MD-Bench/common/util.c

/*
 * Copyright (C) 2022 NHR@FAU, University Erlangen-Nuremberg.
 * All rights reserved. This file is part of MD-Bench.
 * Use of this source code is governed by a LGPL-3.0
 * license that can be found in the LICENSE file.
 */
#include <stdlib.h>
#include <string.h>
#include <util.h>

/* Park/Miller RNG w/out MASKING, so as to be like f90s version */
#define IA 16807
#define IM 2147483647
#define AM (1.0/IM)
#define IQ 127773
#define IR 2836
#define MASK 123459876

double myrandom(int* seed) {
    int k= (*seed) / IQ;
    double ans;

    *seed = IA * (*seed - k * IQ) - IR * k;
    if(*seed < 0) *seed += IM;
    ans = AM * (*seed);
    return ans;
}

void random_reset(int *seed, int ibase, double *coord) {
  int i;
  char *str = (char *) &ibase;
  int n = sizeof(int);
  unsigned int hash = 0;

  for (i = 0; i < n; i++) {
    hash += str[i];
    hash += (hash << 10);
    hash ^= (hash >> 6);
  }

  str = (char *) coord;
  n = 3 * sizeof(double);
  for (i = 0; i < n; i++) {
    hash += str[i];
    hash += (hash << 10);
    hash ^= (hash >> 6);
  }

  hash += (hash << 3);
  hash ^= (hash >> 11);
  hash += (hash << 15);

  // keep 31 bits of unsigned int as new seed
  // do not allow seed = 0, since will cause hang in gaussian()

  *seed = hash & 0x7ffffff;
  if (!(*seed)) *seed = 1;

  // warm up the RNG

  for (i = 0; i < 5; i++) myrandom(seed);
  //save = 0;
}

int str2ff(const char *string) {
    if(strncmp(string, "lj", 2) == 0) return FF_LJ;
    if(strncmp(string, "eam", 3) == 0) return FF_EAM;
    if(strncmp(string, "dem", 3) == 0) return FF_DEM;
    return -1;
}

const char* ff2str(int ff) {
    if(ff == FF_LJ) { return "lj"; }
    if(ff == FF_EAM) { return "eam"; }
    if(ff == FF_DEM) { return "dem"; }
    return "invalid";
}

int get_num_threads() {
    const char *num_threads_env = getenv("NUM_THREADS");
    return (num_threads_env == NULL) ? 32 : atoi(num_threads_env);
}