ParallelTopology.cc

// -*- tab-width: 2; indent-tabs-mode: nil; coding: utf-8-with-signature -*-
//-----------------------------------------------------------------------------
// Copyright 2000-2026 CEA (www.cea.fr) IFPEN (www.ifpenergiesnouvelles.com)
// See the top-level COPYRIGHT file for details.
// SPDX-License-Identifier: Apache-2.0
//-----------------------------------------------------------------------------
/*---------------------------------------------------------------------------*/
/* ParallelTopology.cc                                         (C) 2000-2026 */
/*                                                                           */
/* Information on the core allocation topology.                              */
/*---------------------------------------------------------------------------*/
/*---------------------------------------------------------------------------*/
 
#include "arcane/utils/NotImplementedException.h"
#include "arcane/utils/TraceInfo.h"
#include "arcane/utils/Array.h"
#include "arcane/utils/ITraceMng.h"
#include "arcane/utils/PlatformUtils.h"
 
#include "arcane/core/IParallelMng.h"
 
#include "arcane/impl/ParallelTopology.h"
 
#include <map>
#include <algorithm>
#include <cstring>
 
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namespace Arcane
{
 
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/*---------------------------------------------------------------------------*/
 
ParallelTopology::
ParallelTopology(IParallelMng* pm)
: m_parallel_mng(pm)
, m_machine_rank(-1)
, m_process_rank(-1)
, m_is_machine_master(false)
, m_is_process_master(false)
{
}
 
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void ParallelTopology::
initialize()
{
  // Test to ensure everyone calls this initialization method.
  m_parallel_mng->barrier();
  _init();
}
 
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/*---------------------------------------------------------------------------*/
 
namespace
{
  // Contains node name + pid to know the master ranks per process.
  class NamePid
  {
   public:
 
    NamePid(ByteConstArrayView _name, Int64 _pid)
    : name(_name)
    , pid(_pid)
    {}
 
   public:
 
    ByteConstArrayView name;
    Int64 pid;
    bool operator<(const NamePid& b) const
    {
      int s = std::strcmp((const char*)name.data(), (const char*)b.name.data());
      if (s != 0)
        return s > 0;
      return pid > b.pid;
    }
  };
  // Comparator for the node name.
  class _Comparer
  {
   public:
 
    bool operator()(ByteConstArrayView a, ByteConstArrayView b) const
    {
      return ::strcmp((const char*)a.data(), (const char*)b.data()) > 0;
    }
  };
} // namespace
 
void ParallelTopology::
_init()
{
  IParallelMng* pm = m_parallel_mng;
  ITraceMng* tm = m_parallel_mng->traceMng();
  Int32 nb_rank = pm->commSize();
  Int32 my_rank = pm->commRank();
 
  String host_name = platform::getHostName();
  Int64 pid = platform::getProcessId();
  // All ranks with the same host_name are on the same machine
  Integer len = host_name.utf8().size() + 1;
  Integer max_len = pm->reduce(Parallel::ReduceMax, len);
  ByteUniqueArray all_names(max_len * nb_rank);
  ByteUniqueArray my_name;
  Int64UniqueArray all_pids(nb_rank);
 
  my_name.copy(host_name.utf8()); // copy shrink array size to arg size
  my_name.resize(max_len, '\0'); // add \0 to fill up to max_len
 
  pm->allGather(my_name, all_names);
  pm->allGather(Int64ConstArrayView(1, &pid), all_pids);
 
  m_machine_ranks.clear();
  m_process_ranks.clear();
 
  typedef std::map<ByteConstArrayView, Int32, _Comparer> MasterRankMap;
  typedef std::map<NamePid, Int32> MasterProcessRankMap;
 
  MasterRankMap machine_ranks_map;
  MasterProcessRankMap process_ranks_map;
 
  for (Integer irank = 0; irank < nb_rank; ++irank) {
    ByteConstArrayView rank_name(max_len, &all_names[max_len * irank]);
    bool is_same_name = true;
    for (Integer j = 0; j < max_len; ++j)
      if (rank_name[j] != my_name[j]) {
        is_same_name = false;
        break;
      }
    bool is_same_process = false;
    if (is_same_name && all_pids[irank] == pid)
      is_same_process = true;
 
    if (is_same_name)
      m_machine_ranks.add(irank);
    if (is_same_process)
      m_process_ranks.add(irank);
    {
      MasterRankMap::iterator i_master = machine_ranks_map.find(rank_name);
      if (i_master == machine_ranks_map.end()) {
        // Since the rank traversal is in rank order,
        // the master rank is the first encountered.
        machine_ranks_map.insert(std::make_pair(rank_name, irank));
      }
    }
 
    {
      NamePid mp(rank_name, all_pids[irank]);
      MasterProcessRankMap::iterator i_master = process_ranks_map.find(mp);
      if (i_master == process_ranks_map.end()) {
        process_ranks_map.insert(std::make_pair(mp, irank));
      }
    }
 
    tm->info(4) << "NAME RANK=" << irank << " n=" << (const char*)rank_name.data()
                << " same_rank=" << is_same_name
                << " same_process=" << is_same_process;
  }
 
  // The ranks in m_machine_ranks and m_process_ranks are sorted
  // in ascending order. We consider the master to be the first
  // in the list.
  if (m_machine_ranks[0] == my_rank)
    m_is_machine_master = true;
  if (m_process_ranks[0] == my_rank)
    m_is_process_master = true;
 
  m_master_machine_ranks.clear();
  for (MasterRankMap::const_iterator i(machine_ranks_map.begin()); i != machine_ranks_map.end(); ++i)
    m_master_machine_ranks.add(i->second);
  std::sort(std::begin(m_master_machine_ranks), std::end(m_master_machine_ranks));
  for (Integer i = 0, n = m_master_machine_ranks.size(); i < n; ++i) {
    if (m_master_machine_ranks[i] == m_machine_ranks[0]) {
      m_machine_rank = i;
      break;
    }
  }
 
  m_master_process_ranks.clear();
  for (MasterProcessRankMap::const_iterator i(process_ranks_map.begin()); i != process_ranks_map.end(); ++i)
    m_master_process_ranks.add(i->second);
  std::sort(std::begin(m_master_process_ranks), std::end(m_master_process_ranks));
  for (Integer i = 0, n = m_master_process_ranks.size(); i < n; ++i) {
    if (m_master_process_ranks[i] == m_process_ranks[0]) {
      m_process_rank = i;
      break;
    }
  }
  tm->info(4) << " MachineRank=" << m_machine_rank
              << " ProcessRank=" << m_process_rank;
}
 
/*---------------------------------------------------------------------------*/
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IParallelMng* ParallelTopology::
parallelMng() const
{
  return m_parallel_mng;
}
 
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bool ParallelTopology::
isMasterMachine() const
{
  return m_is_machine_master;
}
 
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Int32ConstArrayView ParallelTopology::
machineRanks() const
{
  return m_machine_ranks;
}
 
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Int32 ParallelTopology::
machineRank() const
{
  return m_machine_rank;
}
 
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bool ParallelTopology::
isMasterProcess() const
{
  return m_is_process_master;
}
 
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Int32ConstArrayView ParallelTopology::
processRanks() const
{
  return m_process_ranks;
}
 
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Int32 ParallelTopology::
processRank() const
{
  return m_process_rank;
}
 
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Int32ConstArrayView ParallelTopology::
masterMachineRanks() const
{
  return m_master_machine_ranks;
}
 
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Int32ConstArrayView ParallelTopology::
masterProcessRanks() const
{
  return m_master_process_ranks;
}
 
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} // namespace Arcane
 
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