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//-----------------------------------------------------------------------------
//
// Copyright (C) Microsoft Corporation. All Rights Reserved.
//
//-----------------------------------------------------------------------------
using System.Collections.Generic;
using System.Diagnostics.Contracts;
namespace Microsoft.Boogie {
public delegate System.Collections.IEnumerable/*<Node!>*//*!*/ Adjacency<T>(T/*!*/ node);
// An SCC is a set of nodes
public sealed class SCC<Node> : ICollection<Node> {
[ContractInvariantMethod]
void ObjectInvariant() {
Contract.Invariant(nodesMap != null);
}
private IDictionary<Node, object>/*!*/ nodesMap = new Dictionary<Node, object>();
private ICollection<Node>/*!*/ nodes {
get {
return cce.NonNull(nodesMap.Keys);
}
}
[Pure]
[GlobalAccess(false)]
[Escapes(true, false)]
System.Collections.IEnumerator/*!*/ System.Collections.IEnumerable.GetEnumerator() {
Contract.Ensures(Contract.Result<System.Collections.IEnumerator>() != null);
return ((System.Collections.IEnumerable)nodes).GetEnumerator();
}
[Pure]
[GlobalAccess(false)]
[Escapes(true, false)]
IEnumerator<Node>/*!*/ IEnumerable<Node>.GetEnumerator() {
Contract.Ensures(Contract.Result<IEnumerator<Node>>() != null);
return ((IEnumerable<Node>)nodes).GetEnumerator();
}
public int Count {
get {
return nodes.Count;
}
}
public bool IsReadOnly {
get {
return nodesMap.IsReadOnly;
}
}
public void Add(Node item) {
nodesMap.Add(item, null);
}
public void Clear() {
nodesMap.Clear();
}
[Pure]
public bool Contains(Node item) {
return nodesMap.ContainsKey(item);
}
public void CopyTo(Node[] array, int arrayIndex) {
//Contract.Requires(array != null);
nodes.CopyTo(array, arrayIndex);
}
public bool Remove(Node item) {
return nodesMap.Remove(item);
}
}
public sealed class StronglyConnectedComponents<Node> : IEnumerable<SCC<Node>/*!*/> {
private readonly IDictionary<Node/*!*/, object/*!*/>/*!*/ graph;
[ContractInvariantMethod]
void graphInvariantMethod() {
Contract.Invariant(cce.NonNullElements(graph));
Contract.Invariant(preds != null);
Contract.Invariant(succs != null);
}
private readonly Adjacency<Node>/*!*/ preds;
private readonly Adjacency<Node>/*!*/ succs;
private bool computed = false;
public bool Computed {
get {
return computed;
}
}
[NotDelayed]
public StronglyConnectedComponents(System.Collections.IEnumerable/*<Node!>*/ graph, Adjacency<Node> preds, Adjacency<Node> succs)
: base() {//BASEMOVE DANGER
Contract.Requires(succs != null);
Contract.Requires(preds != null);
Contract.Requires(graph != null);
Contract.Ensures(!Computed);
IDictionary<Node/*!*/, object>/*!*/ dict = new Dictionary<Node/*!*/, object>();
foreach (Node/*!*/ n in graph) {
Contract.Assert(n != null);
dict.Add(n, null);
}
this.graph = dict;
this.preds = preds;
this.succs = succs;
//:base();
}
[Pure]
[GlobalAccess(false)]
[Escapes(true, false)]
System.Collections.IEnumerator/*!*/ System.Collections.IEnumerable.GetEnumerator() {
Contract.Ensures(Contract.Result<System.Collections.IEnumerator>() != null);
return ((System.Collections.IEnumerable)sccs).GetEnumerator();
}
[Pure]
[GlobalAccess(false)]
[Escapes(true, false)]
IEnumerator<SCC<Node>/*!*/>/*!*/ IEnumerable<SCC<Node>/*!*/>.GetEnumerator() {
Contract.Ensures(Contract.Result<IEnumerator<SCC<Node>>>() != null);
Contract.Assume(Computed);
Contract.Assert(cce.NonNullElements((IEnumerable<SCC<Node>/*!*/>)sccs));//REVIEW
return ((IEnumerable<SCC<Node>/*!*/>)sccs).GetEnumerator();
}
private readonly IList<SCC<Node>/*!*/>/*!*/ sccs = new List<SCC<Node>/*!*/>();
[ContractInvariantMethod]
void sccsInvariant() {
Contract.Invariant(cce.NonNullElements(sccs));
}
public void Compute() {
Contract.Requires(!Computed);
Contract.Ensures(Computed);
// Compute post times on graph with edges reversed
this.dfsNext = this.preds;
foreach (Node/*!*/ n in cce.NonNull(graph.Keys)) {
Contract.Assert(n != null);
if (!seen.ContainsKey(n)) {
OrderNodes(n);
}
}
// Clear seen
seen.Clear();
// Compute SCCs
this.dfsNext = this.succs;
while (postOrder.Count > 0) {
Node/*!*/ n = postOrder.Pop();
Contract.Assert(n != null);
if (!seen.ContainsKey(n)) {
SCC<Node>/*!*/ curr = new SCC<Node>();
FindSCCs(n, curr);
sccs.Add(curr);
}
}
// Clear seen
seen.Clear();
this.computed = true;
}
private Adjacency<Node>/*?*/ dfsNext = null;
private readonly IDictionary<Node/*!*/, object>/*!*/ seen = new Dictionary<Node/*!*/, object>();
private readonly Stack<Node/*!*/>/*!*/ postOrder = new Stack<Node/*!*/>();
[ContractInvariantMethod]
void ObjectInvariant() {
Contract.Invariant(seen != null && cce.NonNullElements(seen.Keys));
Contract.Invariant(cce.NonNullElements(postOrder));
}
// DFS to order nodes by post times
private void OrderNodes(Node node) {
Contract.Requires(node != null);
seen.Add(node, null);
Contract.Assert(dfsNext != null);
System.Collections.IEnumerable/*!*/ nexts = dfsNext(node);
Contract.Assert(nexts != null);
foreach (Node/*!*/ n in nexts) {
Contract.Assert(n != null);
if (graph.ContainsKey(n) && !seen.ContainsKey(n)) {
OrderNodes(n);
}
}
postOrder.Push(node);
}
// DFS to compute SCCs
private void FindSCCs(Node node, SCC<Node> currSCC) {
Contract.Requires(currSCC != null);
Contract.Requires(node != null);
//modifies currSCC.*;
seen.Add(node, null);
currSCC.Add(node);
Contract.Assert(dfsNext != null);
System.Collections.IEnumerable/*!*/ nexts = dfsNext(node);
Contract.Assert(nexts != null);
foreach (Node/*!*/ n in nexts) {
Contract.Assert(n != null);
if (graph.ContainsKey(n) && !seen.ContainsKey(n)) {
FindSCCs(n, currSCC);
}
}
}
[Pure]
public override string ToString() {
Contract.Ensures(Contract.Result<string>() != null);
string outStr = "";
int i = 0;
foreach (ICollection<Node> component in this) {
string/*!*/ tmp = System.String.Format("\nComponent #{0} = ", i++);
Contract.Assert(tmp != null);
outStr += tmp;
bool firstInRow = true;
foreach (Node b in component) {
string/*!*/ tmpComponent = System.String.Format("{0}{1}", firstInRow ? "" : ", ", b);
Contract.Assert(tmpComponent != null);
outStr += tmpComponent;
firstInRow = false;
}
}
return outStr;
}
}
}
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