cs_parall.h

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#ifndef __CS_PARALL_H__
#define __CS_PARALL_H__

/*============================================================================
 * Functions dealing with parallelism
 *============================================================================*/

/*
  This file is part of Code_Saturne, a general-purpose CFD tool.

  Copyright (C) 1998-2021 EDF S.A.

  This program is free software; you can redistribute it and/or modify it under
  the terms of the GNU General Public License as published by the Free Software
  Foundation; either version 2 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 General Public License along with
  this program; if not, write to the Free Software Foundation, Inc., 51 Franklin
  Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/

/*----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
 *  Local headers
 *----------------------------------------------------------------------------*/

#include "cs_defs.h"

/*----------------------------------------------------------------------------*/

BEGIN_C_DECLS

/*=============================================================================
 * Public function prototypes
 *============================================================================*/

/*----------------------------------------------------------------------------
 * Sum values of a counter on all default communicator processes.
 *
 * parameters:
 *   cpt <-> local counter in, global counter out (size: n)
 *   n   <-- number of values
 *----------------------------------------------------------------------------*/

#if defined(HAVE_MPI_IN_PLACE)

inline static void
cs_parall_counter(cs_gnum_t   cpt[],
                  const int   n)
{
  if (cs_glob_n_ranks > 1) {
    MPI_Allreduce(MPI_IN_PLACE, cpt, n, CS_MPI_GNUM, MPI_SUM,
                  cs_glob_mpi_comm);
  }
}

#elif defined(HAVE_MPI)

void
cs_parall_counter(cs_gnum_t   cpt[],
                  const int   n);

#else

#define cs_parall_counter(_cpt, _n)

#endif

/*----------------------------------------------------------------------------
 * Maximum values of a counter on all default communicator processes.
 *
 * parameters:
 *   cpt <-> local counter in, global counter out (size: n)
 *   n   <-> number of values
 *----------------------------------------------------------------------------*/

#if defined(HAVE_MPI_IN_PLACE)

inline static void
cs_parall_counter_max(cs_lnum_t   cpt[],
                      const int   n)
{
  if (cs_glob_n_ranks > 1) {
    MPI_Allreduce(MPI_IN_PLACE, cpt, n, CS_MPI_LNUM, MPI_MAX,
                  cs_glob_mpi_comm);
  }
}

#elif defined(HAVE_MPI)

void
cs_parall_counter_max(cs_lnum_t   cpt[],
                      const int   n);

#else

#define cs_parall_counter_max(_cpt, _n)

#endif

/*----------------------------------------------------------------------------
 * Sum values of a given datatype on all default communicator processes.
 *
 * parameters:
 *   n        <-- number of values
 *   datatype <-- matching Code_Saturne datatype
 *   val      <-> local sum in, global sum out (array)
 *----------------------------------------------------------------------------*/

#if defined(HAVE_MPI_IN_PLACE)

inline static void
cs_parall_sum(int             n,
              cs_datatype_t   datatype,
              void           *val)
{
  if (cs_glob_n_ranks > 1) {
    MPI_Allreduce(MPI_IN_PLACE, val, n, cs_datatype_to_mpi[datatype], MPI_SUM,
                  cs_glob_mpi_comm);
  }
}

#elif defined(HAVE_MPI)

void
cs_parall_sum(int             n,
              cs_datatype_t   datatype,
              void           *val);

#else

#define cs_parall_sum(_n, _datatype, _val) { };

#endif

/*----------------------------------------------------------------------------
 * Maximum values of a given datatype on all default communicator processes.
 *
 * parameters:
 *   n        <-- number of values
 *   datatype <-- matching Code_Saturne datatype
 *   val      <-> local value  input, global value output (array)
 *----------------------------------------------------------------------------*/

#if defined(HAVE_MPI_IN_PLACE)

inline static void
cs_parall_max(int             n,
              cs_datatype_t   datatype,
              void           *val)
{
  if (cs_glob_n_ranks > 1) {
    MPI_Allreduce(MPI_IN_PLACE, val, n, cs_datatype_to_mpi[datatype], MPI_MAX,
                  cs_glob_mpi_comm);
  }
}

#elif defined(HAVE_MPI)

void
cs_parall_max(int             n,
              cs_datatype_t   datatype,
              void           *val);

#else

#define cs_parall_max(_n, _datatype, _val);

#endif

/*----------------------------------------------------------------------------
 * Minimum values of a given datatype on all default communicator processes.
 *
 * parameters:
 *   n        <-- number of values
 *   datatype <-- matching Code_Saturne datatype
 *   val      <-> local value  input, global value output (array)
 *----------------------------------------------------------------------------*/

#if defined(HAVE_MPI_IN_PLACE)

inline static void
cs_parall_min(int             n,
              cs_datatype_t   datatype,
              void           *val)
{
  if (cs_glob_n_ranks > 1) {
    MPI_Allreduce(MPI_IN_PLACE, val, n, cs_datatype_to_mpi[datatype], MPI_MIN,
                  cs_glob_mpi_comm);
  }
}

#elif defined(HAVE_MPI)

void
cs_parall_min(int             n,
              cs_datatype_t   datatype,
              void           *val);

#else

#define cs_parall_min(_n, _datatype, _val);

#endif

/*----------------------------------------------------------------------------
 * Broadcast values of a given datatype to all
 * default communicator processes.
 *
 * parameters:
 *   root_rank <-- rank from which to broadcast
 *   n         <-- number of values
 *   datatype  <-- matching Code_Saturne datatype
 *   val       <-- values to broadcast; input on root_rank,
 *                 output on others (size: n)
 *----------------------------------------------------------------------------*/

#if defined(HAVE_MPI)

inline static void
cs_parall_bcast(int             root_rank,
                int             n,
                cs_datatype_t   datatype,
                void           *val)
{
  if (cs_glob_n_ranks > 1)
    MPI_Bcast(val, n, cs_datatype_to_mpi[datatype], root_rank,
              cs_glob_mpi_comm);
}

#else

#define cs_parall_bcast(_root_rank, _n, _datatype, _val);

#endif

/*----------------------------------------------------------------------------
 * Build a global array from each local array in each domain.
 *
 * Local arrays are appended in order of owning MPI rank.
 * The size of each local array may be different.
 *
 * Use of this function may be quite practical, but should be limited
 * to user functions, as it may limit scalability (especially as regards
 * memory usage).
 *
 * parameters:
 *   n_elts   <-- size of the local array
 *   n_g_elts <-- size of the global array
 *   array    <-- local array (size: n_elts)
 *   g_array  --> global array  (size: n_g_elts)
 *----------------------------------------------------------------------------*/

void
cs_parall_allgather_r(int        n_elts,
                      int        n_g_elts,
                      cs_real_t  array[],
                      cs_real_t  g_array[]);

/*----------------------------------------------------------------------------
 * Maximum value of a real and the value of related array on all
 * default communicator processes.
 *
 * parameters:
 *   n            <-- size of the related array
 *   max          <-> local max in, global max out
 *   max_loc_vals <-> array values at location of local max in,
 *                    and at location of global max out
 *----------------------------------------------------------------------------*/

void
cs_parall_max_loc_vals(int         n,
                       cs_real_t  *max,
                       cs_real_t   max_loc_vals[]);

/*----------------------------------------------------------------------------
 * Minimum value of a real and the value of related array on all
 * default communicator processes.
 *
 * parameters:
 *   n            <-- size of the related array
 *   min          <-> local min in, global min out
 *   min_loc_vals <-> array values at location of local min in,
 *                    and at location of global min out
 *----------------------------------------------------------------------------*/

void
cs_parall_min_loc_vals(int         n,
                       cs_real_t  *min,
                       cs_real_t   min_loc_vals[]);

/*----------------------------------------------------------------------------
 * Given an (id, rank, value) tuple, return the local id and rank
 * corresponding to the global minimum value.
 *
 * parameters:
 *   elt_id  <-> element id for which the value is the smallest
 *               (local in, global out)
 *   rank_id <-> rank id for which the value is the smallest
 *               (local in, global out)
 *   val     <-- associated local minimum value
 *----------------------------------------------------------------------------*/

void
cs_parall_min_id_rank_r(cs_lnum_t  *elt_id,
                        int        *rank_id,
                        cs_real_t   dis2mn);

/*----------------------------------------------------------------------------
 * Return minimum recommended scatter or gather buffer size.
 *
 * This is used by some internal part to block or scatter/gather algorithms,
 * so as to allow I/O buffer size tuning.
 *
 * returns:
 *   minimum recommended part to block or gather buffer size (in bytes)
 *----------------------------------------------------------------------------*/

size_t
cs_parall_get_min_coll_buf_size(void);

/*----------------------------------------------------------------------------
 * Define minimum recommended gather buffer size.
 *
 * This is used by some internal part to block or scatter/gather algorithms,
 * so as to allow I/O buffer size tuning.
 *
 * parameters:
 *   minimum recommended part to block or gather buffer size (in bytes)
 *----------------------------------------------------------------------------*/

void
cs_parall_set_min_coll_buf_size(size_t buffer_size);

/*----------------------------------------------------------------------------*/

END_C_DECLS

#endif /* __CS_PARALL_H__ */