fof.c

/*******************************************************************************
 * This file is part of SWIFT.
 * Copyright (c) 2018 James Willis (james.s.willis@durham.ac.uk)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 ******************************************************************************/

/* Config parameters. */
#include "../config.h"

/* Some standard headers. */
#include <errno.h>
#include <libgen.h>
#include <unistd.h>

/* MPI headers. */
#ifdef WITH_MPI
#include <mpi.h>
#endif

/* This object's header. */
#include "fof.h"

/* Local headers. */
#include "threadpool.h"
#include "engine.h"
#include "proxy.h"
#include "common_io.h"

#ifdef WITH_MPI
MPI_Datatype fof_mpi_type;
#endif
FILE *fof_file;
int node_offset;

/* Initialises parameters for the FOF search. */
void fof_init(struct space *s, long long Ngas, long long Ngparts) {

  struct engine *e = s->e;

  /* Check that we can write outputs by testing if the output
   * directory exists and is searchable and writable. */
  parser_get_param_string(e->parameter_file, "FOF:basename", s->fof_data.base_name);
  
  const char *dirp = dirname(s->fof_data.base_name);
  if (access(dirp, W_OK | X_OK) != 0) {
    error("Cannot write FOF outputs in directory %s (%s)", dirp, strerror(errno));
  }

  /* Read the minimum group size. */
  s->fof_data.min_group_size = parser_get_opt_param_int(e->parameter_file, "FOF:min_group_size", 20);
  
  /* Read the linking length scale. */
  const double l_x_scale = parser_get_opt_param_double(e->parameter_file, "FOF:linking_length_scale", 0.2);

  /* Calculate the particle linking length based upon the mean inter-particle
   * spacing of the DM particles. */
  const int total_nr_dmparts = Ngparts - Ngas;