vtkBlockDistribution.h

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// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-FileCopyrightText: Copyright (C) 2008 The Trustees of Indiana University.
// SPDX-License-Identifier: BSD-3-Clause AND BSL-1.0
#ifndef vtkBlockDistribution_h
#define vtkBlockDistribution_h
 
#include "vtkABINamespace.h"
 
VTK_ABI_NAMESPACE_BEGIN
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;
}
 
VTK_ABI_NAMESPACE_END
#endif
// VTK-HeaderTest-Exclude: vtkBlockDistribution.h