1 //===- llvm/Analysis/MaximumSpanningTree.h - Interface ----------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This module privides means for calculating a maximum spanning tree for a
11 // given set of weighted edges. The type parameter T is the type of a node.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_ANALYSIS_MAXIMUMSPANNINGTREE_H
16 #define LLVM_ANALYSIS_MAXIMUMSPANNINGTREE_H
18 #include "llvm/BasicBlock.h"
19 #include "llvm/ADT/EquivalenceClasses.h"
25 /// MaximumSpanningTree - A MST implementation.
26 /// The type parameter T determines the type of the nodes of the graph.
28 class MaximumSpanningTree {
30 // A comparing class for comparing weighted edges.
31 template <typename CT>
32 struct EdgeWeightCompare {
33 bool operator()(typename MaximumSpanningTree<CT>::EdgeWeight X,
34 typename MaximumSpanningTree<CT>::EdgeWeight Y) const {
35 if (X.second > Y.second) return true;
36 if (X.second < Y.second) return false;
37 if (const BasicBlock *BBX = dyn_cast<BasicBlock>(X.first.first)) {
38 if (const BasicBlock *BBY = dyn_cast<BasicBlock>(Y.first.first)) {
39 if (BBX->size() > BBY->size()) return true;
40 if (BBX->size() < BBY->size()) return false;
43 if (const BasicBlock *BBX = dyn_cast<BasicBlock>(X.first.second)) {
44 if (const BasicBlock *BBY = dyn_cast<BasicBlock>(Y.first.second)) {
45 if (BBX->size() > BBY->size()) return true;
46 if (BBX->size() < BBY->size()) return false;
54 typedef std::pair<const T*, const T*> Edge;
55 typedef std::pair<Edge, double> EdgeWeight;
56 typedef std::vector<EdgeWeight> EdgeWeights;
58 typedef std::vector<Edge> MaxSpanTree;
63 static char ID; // Class identification, replacement for typeinfo
65 /// MaximumSpanningTree() - Takes a vector of weighted edges and returns a
67 MaximumSpanningTree(EdgeWeights &EdgeVector) {
69 std::stable_sort(EdgeVector.begin(), EdgeVector.end(), EdgeWeightCompare<T>());
71 // Create spanning tree, Forest contains a special data structure
72 // that makes checking if two nodes are already in a common (sub-)tree
74 EquivalenceClasses<const T*> Forest;
75 for (typename EdgeWeights::iterator EWi = EdgeVector.begin(),
76 EWe = EdgeVector.end(); EWi != EWe; ++EWi) {
77 Edge e = (*EWi).first;
79 Forest.insert(e.first);
80 Forest.insert(e.second);
83 // Iterate over the sorted edges, biggest first.
84 for (typename EdgeWeights::iterator EWi = EdgeVector.begin(),
85 EWe = EdgeVector.end(); EWi != EWe; ++EWi) {
86 Edge e = (*EWi).first;
88 if (Forest.findLeader(e.first) != Forest.findLeader(e.second)) {
89 Forest.unionSets(e.first, e.second);
90 // So we know now that the edge is not already in a subtree, so we push
91 // the edge to the MST.
97 typename MaxSpanTree::iterator begin() {
101 typename MaxSpanTree::iterator end() {
106 } // End llvm namespace