mirror of
https://gitlab.kitware.com/vtk/vtk-m
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101 lines
3.4 KiB
C++
101 lines
3.4 KiB
C++
//============================================================================
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// Copyright (c) Kitware, Inc.
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// All rights reserved.
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// See LICENSE.txt for details.
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//
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// This software is distributed WITHOUT ANY WARRANTY; without even
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// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the above copyright notice for more information.
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//============================================================================
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#ifndef vtk_m_worklet_connectivity_graph_connectivity_h
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#define vtk_m_worklet_connectivity_graph_connectivity_h
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#include <vtkm/cont/Invoker.h>
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#include <vtkm/worklet/connectivities/CellSetDualGraph.h>
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#include <vtkm/worklet/connectivities/InnerJoin.h>
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#include <vtkm/worklet/connectivities/UnionFind.h>
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namespace vtkm
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{
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namespace worklet
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{
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namespace connectivity
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{
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namespace detail
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{
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class GraphGraft : public vtkm::worklet::WorkletMapField
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{
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public:
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using ControlSignature = void(FieldIn start,
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FieldIn degree,
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WholeArrayIn ids,
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AtomicArrayInOut comp);
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using ExecutionSignature = void(WorkIndex, _1, _2, _3, _4);
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template <typename InPortalType, typename AtomicCompInOut>
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VTKM_EXEC void operator()(vtkm::Id index,
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vtkm::Id start,
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vtkm::Id degree,
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const InPortalType& conn,
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AtomicCompInOut& comp) const
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{
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for (vtkm::Id offset = start; offset < start + degree; offset++)
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{
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vtkm::Id neighbor = conn.Get(offset);
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// We need to reload thisComp and thatComp every iteration since
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// they might have been changed by Unite() both as a result of
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// attaching one tree to the other or as a result of path compression
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// in findRoot().
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auto thisComp = comp.Get(index);
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auto thatComp = comp.Get(neighbor);
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// Merge the two components one way or the other, the order will
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// be resolved by Unite().
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UnionFind::Unite(comp, thisComp, thatComp);
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}
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}
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};
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}
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// Single pass connected component algorithm from
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// Jaiganesh, Jayadharini, and Martin Burtscher.
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// "A high-performance connected components implementation for GPUs."
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// Proceedings of the 27th International Symposium on High-Performance
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// Parallel and Distributed Computing. 2018.
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class GraphConnectivity
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{
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public:
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template <typename InputArrayType, typename OutputArrayType>
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void Run(const InputArrayType& numIndicesArray,
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const InputArrayType& indexOffsetsArray,
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const InputArrayType& connectivityArray,
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OutputArrayType& componentsOut) const
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{
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VTKM_IS_ARRAY_HANDLE(InputArrayType);
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VTKM_IS_ARRAY_HANDLE(OutputArrayType);
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using Algorithm = vtkm::cont::Algorithm;
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// Initialize the parent pointer to point to the node itself. There are other
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// ways to initialize the parent pointers, for example, a smaller or the minimal
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// neighbor.
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Algorithm::Copy(vtkm::cont::ArrayHandleIndex(numIndicesArray.GetNumberOfValues()),
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componentsOut);
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vtkm::cont::Invoker invoke;
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invoke(
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detail::GraphGraft{}, indexOffsetsArray, numIndicesArray, connectivityArray, componentsOut);
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invoke(PointerJumping{}, componentsOut);
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// renumber connected component to the range of [0, number of components).
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Renumber::Run(componentsOut);
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}
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};
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}
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}
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}
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#endif //vtk_m_worklet_connectivity_graph_connectivity_h
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