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Open-source constraint solver.
/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2023, IMT Atlantique. All rights reserved.
*
* Licensed under the BSD 4-clause license.
*
* See LICENSE file in the project root for full license information.
*/
package org.chocosolver.util.graphOperations.dominance;
import gnu.trove.list.array.TIntArrayList;
import org.chocosolver.util.objects.graphs.DirectedGraph;
import org.chocosolver.util.objects.setDataStructures.ISet;
import org.chocosolver.util.objects.setDataStructures.ISetIterator;
import org.chocosolver.util.objects.setDataStructures.SetType;
import java.util.Iterator;
/**
* Class that finds dominators of a given flow graph g(s)
*/
public abstract class AbstractLengauerTarjanDominatorsFinder {
//***********************************************************************************
// VARIABLES
//***********************************************************************************
// flow graph
protected DirectedGraph g;
// dominator tree
protected DirectedGraph T;
protected int root, n, k;
protected int[] parent, vertex, bucket, ancestor, label, semi, dom;
protected ISet[] succs;
protected ISet[] preds;
protected Iterator[] iterator;
protected TIntArrayList list;
//***********************************************************************************
// CONSTRUCTORS
//***********************************************************************************
/**
* Object that finds dominators of the given flow graph g(s)
*/
public AbstractLengauerTarjanDominatorsFinder(int s, DirectedGraph g) {
root = s;
n = g.getNbMaxNodes();
this.g = g;
parent = new int[n];
semi = new int[n];
dom = new int[n];
ancestor = new int[n];
label = new int[n];
vertex = new int[n];
bucket = new int[n];
succs = new ISet[n];
preds = new ISet[n];
//noinspection unchecked
iterator = new Iterator[n];
T = new DirectedGraph(n, SetType.LINKED_LIST, false);
list = new TIntArrayList();
}
//***********************************************************************************
// INITIALIZATION
//***********************************************************************************
/**
* Find immediate dominators of the given graph
* and preprocess dominance requests
*
* @return false iff the source cannot reach all nodes (contradiction)
*/
public boolean findDominators() {
initParams(false);
DFS();
if (k != n - 1) {
return false;
}
findAllIdom();
preprocessDominanceRequests();
return true;
}
/**
* Find immediate postdominators of the given graph
* and preprocess dominance requests
* post dominators are dominators of the inverse graph
*
* @return false iff the source cannot reach all nodes (contradiction)
*/
public boolean findPostDominators() {
initParams(true);
DFS();
if (k != n - 1) {
return false;
}
findAllIdom();
preprocessDominanceRequests();
return true;
}
protected void initParams(boolean inverseGraph) {
for (int i = 0; i < n; i++) {
T.getSuccessorsOf(i).clear();
T.getPredecessorsOf(i).clear();
if (inverseGraph) {
succs[i] = g.getPredecessorsOf(i);
preds[i] = g.getSuccessorsOf(i);
} else {
succs[i] = g.getSuccessorsOf(i);
preds[i] = g.getPredecessorsOf(i);
}
semi[i] = -1;
ancestor[i] = -1;
bucket[i] = -1;
}
}
private void DFS() {
int node = root;
int next;
k = 0;
semi[node] = k;
label[node] = node;
vertex[k] = node;
for(int i=0;i= 1; i--) {
w = vertex[i];
prds = preds[w].iterator();
while (prds.hasNext()) {
int v = prds.nextInt();
u = eval(v);
if (semi[u] < semi[w]) {
semi[w] = semi[u];
}
}
if (vertex[semi[w]] != parent[w]) {
addToBucket(vertex[semi[w]], w);
} else {
dom[w] = parent[w];
}
link(parent[w], w);
int oldBI = parent[w];
int v = bucket[oldBI];
while (v != -1) {
bucket[oldBI] = -1;
u = eval(v);
if (semi[u] < semi[v]) {
dom[v] = u;
} else {
dom[v] = parent[w];
}
oldBI = v;
v = bucket[v];
}
}
for (int i = 1; i < n; i++) {
w = vertex[i];
if (dom[w] != vertex[semi[w]]) {
dom[w] = dom[dom[w]];
}
T.addEdge(dom[w], w);
}
dom[root] = root;
}
private void addToBucket(int buckIdx, int element) {
if (bucket[buckIdx] == -1) {
bucket[buckIdx] = element;
} else {
int old = bucket[buckIdx];
bucket[buckIdx] = element;
bucket[element] = old;
}
}
//***********************************************************************************
// link-eval
//***********************************************************************************
protected abstract void link(int v, int w);
protected abstract int eval(int v);
protected abstract void compress(int v);
//***********************************************************************************
// ACCESSORS
//***********************************************************************************
/**
* @return the immediate dominator of x in the flow graph
*/
public int getImmediateDominatorsOf(int x) {
return dom[x];
}
/**
* BEWARE requires preprocessDominanceRequests()
*
* @return true iff x is dominated by y
*/
public boolean isDomminatedBy(int x, int y) {
return ancestor[x] > ancestor[y] && semi[x] < semi[y];
}
/**
* Get the dominator tree formed with arcs (x,y)
* such that x is the immediate dominator of y
*
* @return the dominator of the flow graph
*/
public DirectedGraph getDominatorTree() {
return T;
}
/**
* O(n+m) preprocessing for enabling dominance requests in O(1)
* BEWARE : destroy the current data structure (recycling)
*/
private void preprocessDominanceRequests() {
// RECYCLE DATA STRUCTURES
// ancestor = in = opening time = preorder
// semi = out = closing time = postorder
for (int i = 0; i < n; i++) {
parent[i] = -1;
succs[i] = T.getSuccessorsOf(i);
iterator[i] = succs[i].iterator();
}
//PREPROCESSING
int time = 0;
int currentNode = root;
parent[currentNode] = currentNode;
ancestor[currentNode] = 0;
int nextNode;
while (true) {
if(iterator[currentNode].hasNext()){
nextNode = iterator[currentNode].next();
if (parent[nextNode] == -1) {
time++;
ancestor[nextNode] = time;
parent[nextNode] = currentNode;
currentNode = nextNode;
}
}else{
time++;
semi[currentNode] = time;
if (currentNode == root) {
break;
}
currentNode = parent[currentNode];
}
}
}
//***********************************************************************************
// ARC-DOMINATOR //(x,y) existe && x domine y && y domines tous ses autres predecesseurs (sauf x donc)
//***********************************************************************************
}