Ifpack_UserPartitioner.cpp

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//       Ifpack: Object-Oriented Algebraic Preconditioner Package
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#include "Ifpack_ConfigDefs.h"
#include "Ifpack_Partitioner.h"
#include "Ifpack_OverlappingPartitioner.h"
#include "Ifpack_UserPartitioner.h"
#include "Epetra_CrsGraph.h"

//==============================================================================
int Ifpack_UserPartitioner::ComputePartitions()
{
  
  if (Map_ == 0)
    IFPACK_CHK_ERR(-1);

  if(keepSingletons_) {
    // If we're keeping singletons, we need to count them and add a new part
    // per singleton
    int base_num_parts = NumLocalParts();
    int curr_num_parts = base_num_parts;
      
    for (int i = 0 ; i < NumMyRows() ; ++i) {
      if(Map_[i] != -1) 
        Partition_[i] = Map_[i];
      else {
        Partition_[i] = curr_num_parts;
        curr_num_parts++;
      }
    }

    if(curr_num_parts != base_num_parts) {
      NumLocalParts_ = curr_num_parts;
      Parts_.resize(NumLocalParts());
    }
  }
  else {
    // copy the user's vector
    for (int i = 0 ; i < NumMyRows() ; ++i) {
      Partition_[i] = Map_[i];
    }
  }


#if 0
  // put together all partitions composed by 1 one vertex
  // (if any)
  std::vector<int> singletons(NumLocalParts());
  for (unsigned int i = 0 ; i < singletons.size() ; ++i) {
    singletons[i] = 0;
  }


  // may want to uncomment the following to ensure that no
  // partitions are in fact singletons
  for (int i = 0 ; i < NumMyRows() ; ++i) {
    ++singletons[Partition_[i]];
  }
  
  int count = 0;
  for (unsigned int i = 0 ; i < singletons.size() ; ++i) {
    if (singletons[i] == 1)
      ++count;
  }

  int index = -1;
  for (int i = 0 ; i < NumMyRows() ; ++i) {
    int j = Partition_[i];
    if (singletons[j] == 1) {
      if (index == -1)
        index = j;
      else
        Partition_[i] = index;
    }
  }
#endif

  return(0);
}