vtkBlockDistribution.h

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/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkBlockDistribution.h

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
/*
 * Copyright (C) 2008 The Trustees of Indiana University.
 * Use, modification and distribution is subject to the Boost Software
 * License, Version 1.0. (See http://www.boost.org/LICENSE_1_0.txt)
 */
#ifndef vtkBlockDistribution_h
#define vtkBlockDistribution_h

class vtkBlockDistribution
{
public:
  vtkBlockDistribution(vtkIdType N, vtkIdType P);

  vtkIdType GetNumElements() { return this->NumElements; }

  vtkIdType GetNumProcessors() { return this->NumProcessors; }

  vtkIdType GetBlockSize(vtkIdType rank);

  vtkIdType GetProcessorOfElement(vtkIdType globalIndex);

  vtkIdType GetLocalIndexOfElement(vtkIdType globalIndex);

  vtkIdType GetFirstGlobalIndexOnProcessor(vtkIdType rank);

  vtkIdType GetGlobalIndex(vtkIdType localIndex, vtkIdType rank);

private:
  vtkIdType NumElements;
  vtkIdType NumProcessors;
};

// ----------------------------------------------------------------------

inline vtkBlockDistribution::vtkBlockDistribution(vtkIdType N, vtkIdType P)
  : NumElements(N), NumProcessors(P)
{
}

// ----------------------------------------------------------------------

inline vtkIdType vtkBlockDistribution::GetBlockSize(vtkIdType rank)
{
  return (this->NumElements / this->NumProcessors)
       + (rank < this->NumElements % this->NumProcessors? 1 : 0);
}

// ----------------------------------------------------------------------

inline vtkIdType
vtkBlockDistribution::GetProcessorOfElement(vtkIdType globalIndex)
{
  vtkIdType smallBlockSize = this->NumElements / this->NumProcessors;
  vtkIdType cutoffProcessor = this->NumElements % this->NumProcessors;
  vtkIdType cutoffIndex = cutoffProcessor * (smallBlockSize + 1);

  if (globalIndex < cutoffIndex)
  {
    return globalIndex / (smallBlockSize + 1);
  }
  else
  {
    return cutoffProcessor + (globalIndex - cutoffIndex) / smallBlockSize;
  }
}

// ----------------------------------------------------------------------

inline vtkIdType
vtkBlockDistribution::GetLocalIndexOfElement(vtkIdType globalIndex)
{
  vtkIdType rank = this->GetProcessorOfElement(globalIndex);
  return globalIndex - this->GetFirstGlobalIndexOnProcessor(rank);
}

// ----------------------------------------------------------------------

inline vtkIdType
vtkBlockDistribution::GetFirstGlobalIndexOnProcessor(vtkIdType rank)
{
  vtkIdType estimate = rank * (this->NumElements / this->NumProcessors + 1);
  vtkIdType cutoffProcessor = this->NumElements % this->NumProcessors;
  if (rank < cutoffProcessor)
  {
    return estimate;
  }
  else
  {
    return estimate - (rank - cutoffProcessor);
  }
}

// ----------------------------------------------------------------------

inline vtkIdType
vtkBlockDistribution::GetGlobalIndex(vtkIdType localIndex, vtkIdType rank)
{
  return this->GetFirstGlobalIndexOnProcessor(rank) + localIndex;
}

#endif
// VTK-HeaderTest-Exclude: vtkBlockDistribution.h