nimble.mpi.reduction_utils.h

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#ifndef NIMBLE_MPI_REDUCTION_UTILS
#define NIMBLE_MPI_REDUCTION_UTILS
 
#include <mpi.h>
 
#include <algorithm>
#include <array>
#include <cstring>
#include <exception>
#include <iostream>
#include <memory>
#include <numeric>
#include <string>
#include <tuple>
#include <type_traits>
#include <vector>
 
#include "nimble.mpi.mpicontext.h"
#include "nimble.mpi.serialization.h"
 
namespace nimble {
 
std::vector<int>
PackIDSpace(const std::vector<int>& raw_node_ids, int max_nodes_assigned_to_a_rank, const mpicontext& context);
 
int
GetMaximumNodeId(const std::vector<int>& global_node_ids, const mpicontext& context);
 
std::unique_ptr<int[]>
GetNumberOfNodesAssignedToEachRank(const std::vector<int>& global_node_ids, const mpicontext& context);
 
void
EnsureCheckpoint(const mpicontext& context, const std::string& message);
 
template <class Key, class Val>
std::vector<std::pair<Key, std::vector<Val>>>
GroupConsecutive(const std::vector<std::pair<Key, Val>>& lst)
{
  if (lst.size() == 0) return {};
  std::vector<int> key_ids;
  key_ids.reserve(lst.size() + 1);
  const Key* group_key  = &lst[0].first;
  int        max_key_id = 0;
  int        lst_size   = lst.size();
  for (const std::pair<Key, Val>& p : lst) {
    if (p.first != *group_key) {
      ++max_key_id;
      group_key = &p.first;
    }
    key_ids.push_back(max_key_id);
  }
  key_ids.push_back(max_key_id + 1);
  std::vector<std::pair<Key, std::vector<Val>>> groups;
  groups.reserve(max_key_id + 1);
  {
    int prev_key_id = 0;
    int group_size  = 1;
    for (int i = 1; i <= lst_size; ++i) {
      if (key_ids[i] != prev_key_id) {
        groups.emplace_back(lst[i - 1].first, std::vector<Val>(group_size));
        auto&                      new_elem = groups.back();
        const std::pair<Key, Val>* src_ptr  = &lst[i - group_size];
        for (Val& q : new_elem.second) {
          q = src_ptr->second;
          ++src_ptr;
        }
        group_size  = 1;
        prev_key_id = key_ids[i];
      } else {
        ++group_size;
      }
    }
  }
  return groups;
}
 
}  // namespace nimble
 
#endif  // NIMBLE_MPI_REDUCTION_UTILS