CMake/Source/cmComputeComponentGraph.cxx

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Simplify CMake per-source license notices Per-source copyright/license notice headers that spell out copyright holder names and years are hard to maintain and often out-of-date or plain wrong. Precise contributor information is already maintained automatically by the version control tool. Ultimately it is the receiver of a file who is responsible for determining its licensing status, and per-source notices are merely a convenience. Therefore it is simpler and more accurate for each source to have a generic notice of the license name and references to more detailed information on copyright holders and full license terms. Our `Copyright.txt` file now contains a list of Contributors whose names appeared source-level copyright notices. It also references version control history for more precise information. Therefore we no longer need to spell out the list of Contributors in each source file notice. Replace CMake per-source copyright/license notice headers with a short description of the license and links to `Copyright.txt` and online information available from "https://cmake.org/licensing". The online URL also handles cases of modules being copied out of our source into other projects, so we can drop our notices about replacing links with full license text. Run the `Utilities/Scripts/filter-notices.bash` script to perform the majority of the replacements mechanically. Manually fix up shebang lines and trailing newlines in a few files. Manually update the notices in a few files that the script does not handle.
2016-09-27 22:01:08 +03:00
/* Distributed under the OSI-approved BSD 3-Clause License. See accompanying
file Copyright.txt or https://cmake.org/licensing for details. */
#include "cmComputeComponentGraph.h"
#include <algorithm>
#include <assert.h>
cmComputeComponentGraph::cmComputeComponentGraph(Graph const& input)
: InputGraph(input)
{
// Identify components.
this->Tarjan();
// Compute the component graph.
this->ComponentGraph.resize(0);
this->ComponentGraph.resize(this->Components.size());
this->TransferEdges();
}
cmComputeComponentGraph::~cmComputeComponentGraph()
{
}
void cmComputeComponentGraph::Tarjan()
{
int n = static_cast<int>(this->InputGraph.size());
TarjanEntry entry = { 0, 0 };
this->TarjanEntries.resize(0);
this->TarjanEntries.resize(n, entry);
this->TarjanComponents.resize(0);
this->TarjanComponents.resize(n, -1);
this->TarjanWalkId = 0;
this->TarjanVisited.resize(0);
this->TarjanVisited.resize(n, 0);
for (int i = 0; i < n; ++i) {
// Start a new DFS from this node if it has never been visited.
if (!this->TarjanVisited[i]) {
assert(this->TarjanStack.empty());
++this->TarjanWalkId;
this->TarjanIndex = 0;
this->TarjanVisit(i);
}
}
}
void cmComputeComponentGraph::TarjanVisit(int i)
{
// We are now visiting this node.
this->TarjanVisited[i] = this->TarjanWalkId;
// Initialize the entry.
this->TarjanEntries[i].Root = i;
this->TarjanComponents[i] = -1;
this->TarjanEntries[i].VisitIndex = ++this->TarjanIndex;
this->TarjanStack.push(i);
// Follow outgoing edges.
EdgeList const& nl = this->InputGraph[i];
for (EdgeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni) {
int j = *ni;
// Ignore edges to nodes that have been reached by a previous DFS
// walk. Since we did not reach the current node from that walk
// it must not belong to the same component and it has already
// been assigned to a component.
if (this->TarjanVisited[j] > 0 &&
this->TarjanVisited[j] < this->TarjanWalkId) {
continue;
}
// Visit the destination if it has not yet been visited.
if (!this->TarjanVisited[j]) {
this->TarjanVisit(j);
}
// If the destination has not yet been assigned to a component,
// check if it has a better root for the current object.
if (this->TarjanComponents[j] < 0) {
if (this->TarjanEntries[this->TarjanEntries[j].Root].VisitIndex <
this->TarjanEntries[this->TarjanEntries[i].Root].VisitIndex) {
this->TarjanEntries[i].Root = this->TarjanEntries[j].Root;
}
}
}
// Check if we have found a component.
if (this->TarjanEntries[i].Root == i) {
// Yes. Create it.
int c = static_cast<int>(this->Components.size());
this->Components.push_back(NodeList());
NodeList& component = this->Components[c];
// Populate the component list.
int j;
do {
// Get the next member of the component.
j = this->TarjanStack.top();
this->TarjanStack.pop();
// Assign the member to the component.
this->TarjanComponents[j] = c;
this->TarjanEntries[j].Root = i;
// Store the node in its component.
component.push_back(j);
} while (j != i);
// Sort the component members for clarity.
std::sort(component.begin(), component.end());
}
}
void cmComputeComponentGraph::TransferEdges()
{
// Map inter-component edges in the original graph to edges in the
// component graph.
int n = static_cast<int>(this->InputGraph.size());
for (int i = 0; i < n; ++i) {
int i_component = this->TarjanComponents[i];
EdgeList const& nl = this->InputGraph[i];
for (EdgeList::const_iterator ni = nl.begin(); ni != nl.end(); ++ni) {
int j = *ni;
int j_component = this->TarjanComponents[j];
if (i_component != j_component) {
// We do not attempt to combine duplicate edges, but instead
// store the inter-component edges with suitable multiplicity.
this->ComponentGraph[i_component].push_back(
cmGraphEdge(j_component, ni->IsStrong()));
}
}
}
}