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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
/**
* @class vtkBlockDistribution
* @brief A helper class that manages a block distribution of N elements of data.
*
*
*
*/
#ifndef vtkBlockDistribution_h
#define vtkBlockDistribution_h
#include "vtkABINamespace.h"
VTK_ABI_NAMESPACE_BEGIN
class vtkBlockDistribution
{
public:
/**
* Create a block distribution with N elements on P processors.
*/
vtkBlockDistribution(vtkIdType N, vtkIdType P);
/**
* Retrieves the number of elements for which this block distribution was
* built.
*/
vtkIdType GetNumElements() { return this->NumElements; }
/**
* Retrieves the number of processors for which this block
* distribution was built.
*/
vtkIdType GetNumProcessors() { return this->NumProcessors; }
/**
* Get the block size for the processor with the given rank. This is the
* number of elements that the processor will store.
*/
vtkIdType GetBlockSize(vtkIdType rank);
/**
* Retrieve the process number in [0, GetNumProcessors()) where the element
* with the given global index will be located.
*/
vtkIdType GetProcessorOfElement(vtkIdType globalIndex);
/**
* Retrieve the local index (offset) on the processor determined by
* GetProcessorOfElement that refers to the given global index.
*/
vtkIdType GetLocalIndexOfElement(vtkIdType globalIndex);
/**
* Retrieve the first global index stored on the processor with the given
* rank.
*/
vtkIdType GetFirstGlobalIndexOnProcessor(vtkIdType rank);
/**
* Retrieve the global index associated with the given local index on the
* processor with the given 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
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