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bdca8b01d2
#pragma once is a widely supported compiler pragma, even though it is not part of the C++ standard. Many of the issues keeping #pragma once from being standardized (distributed filesystems, build farms, hard links, etc.) do not apply to CMake - it is easy to build CMake on a single machine. CMake also does not install any header files which can be consumed by other projects (though cmCPluginAPI.h has been deliberately omitted from this conversion in case anyone is still using it.) Finally, #pragma once has been required to build CMake since at least August 2017 (7f29bbe6 enabled server mode unconditionally, which had been using #pragma once since September 2016 (b13d3e0d)). The fact that we now require C++11 filters out old compilers, and it is unlikely that there is a compiler which supports C++11 but does not support #pragma once.
80 lines
2.1 KiB
C++
80 lines
2.1 KiB
C++
/* Distributed under the OSI-approved BSD 3-Clause License. See accompanying
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file Copyright.txt or https://cmake.org/licensing for details. */
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#pragma once
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#include "cmConfigure.h" // IWYU pragma: keep
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#include <stack>
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#include <vector>
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#include "cmGraphAdjacencyList.h"
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/** \class cmComputeComponentGraph
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* \brief Analyze a graph to determine strongly connected components.
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*
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* Convert a directed graph into a directed acyclic graph whose nodes
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* correspond to strongly connected components of the original graph.
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*
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* We use Tarjan's algorithm to enumerate the components efficiently.
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* An advantage of this approach is that the components are identified
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* in a topologically sorted order.
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*/
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class cmComputeComponentGraph
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{
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public:
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// Represent the graph with an adjacency list.
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using NodeList = cmGraphNodeList;
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using EdgeList = cmGraphEdgeList;
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using Graph = cmGraphAdjacencyList;
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cmComputeComponentGraph(Graph const& input);
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~cmComputeComponentGraph();
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/** Run the computation. */
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void Compute();
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/** Get the adjacency list of the component graph. */
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Graph const& GetComponentGraph() const { return this->ComponentGraph; }
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EdgeList const& GetComponentGraphEdges(int c) const
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{
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return this->ComponentGraph[c];
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}
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/** Get map from component index to original node indices. */
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std::vector<NodeList> const& GetComponents() const
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{
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return this->Components;
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}
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NodeList const& GetComponent(int c) const { return this->Components[c]; }
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/** Get map from original node index to component index. */
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std::vector<int> const& GetComponentMap() const
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{
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return this->TarjanComponents;
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}
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private:
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void TransferEdges();
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Graph const& InputGraph;
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Graph ComponentGraph;
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// Tarjan's algorithm.
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struct TarjanEntry
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{
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int Root;
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int VisitIndex;
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};
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std::vector<int> TarjanVisited;
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std::vector<int> TarjanComponents;
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std::vector<TarjanEntry> TarjanEntries;
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std::vector<NodeList> Components;
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std::stack<int> TarjanStack;
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int TarjanWalkId;
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int TarjanIndex;
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void Tarjan();
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void TarjanVisit(int i);
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// Connected components.
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};
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