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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Common / Utils / Boolean / ConversionContext.cs / 1305376 / ConversionContext.cs
//---------------------------------------------------------------------- //// Copyright (c) Microsoft Corporation. All rights reserved. // // // @owner [....] // @backupOwner [....] //--------------------------------------------------------------------- using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Diagnostics; namespace System.Data.Common.Utils.Boolean { ////// Manages state used to translate BoolExpr to decision diagram vertices and back again. /// Specializations exist for generic and DomainConstraint expressions. /// internal abstract class ConversionContext{ /// /// Gets the solver instance associated with this conversion context. Used to reterieve /// canonical Decision Diagram vertices for this context. /// internal readonly Solver Solver = new Solver(); ////// Given a term in BoolExpr, returns the corresponding decision diagram vertex. /// internal abstract Vertex TranslateTermToVertex(TermExprterm); /// /// Describes a vertex as a series of literal->vertex successors such that the literal /// logically implies the given vertex successor. /// internal abstract IEnumerable> GetSuccessors(Vertex vertex); } /// /// VertexLiteral pair, used for ConversionContext.GetSuccessors /// internal sealed class LiteralVertexPair{ internal readonly Vertex Vertex; internal readonly Literal Literal; internal LiteralVertexPair(Vertex vertex, Literal literal) { this.Vertex = vertex; this.Literal = literal; } } /// /// Generic implementation of a ConversionContext /// internal sealed class GenericConversionContext: ConversionContext { readonly Dictionary , int> _variableMap = new Dictionary , int>(); Dictionary > _inverseVariableMap; internal override Vertex TranslateTermToVertex(TermExpr term) { int variable; if (!_variableMap.TryGetValue(term, out variable)) { variable = Solver.CreateVariable(); _variableMap.Add(term, variable); } return Solver.CreateLeafVertex(variable, Solver.BooleanVariableChildren); } internal override IEnumerable > GetSuccessors(Vertex vertex) { LiteralVertexPair [] successors = new LiteralVertexPair [2]; Debug.Assert(2 == vertex.Children.Length); Vertex then = vertex.Children[0]; Vertex @else = vertex.Children[1]; // get corresponding term expression InitializeInverseVariableMap(); TermExpr term = _inverseVariableMap[vertex.Variable]; // add positive successor (then) Literal literal = new Literal (term, true); successors[0] = new LiteralVertexPair (then, literal); // add negative successor (else) literal = literal.MakeNegated(); successors[1] = new LiteralVertexPair (@else, literal); return successors; } private void InitializeInverseVariableMap() { if (null == _inverseVariableMap) { _inverseVariableMap = _variableMap.ToDictionary(kvp => kvp.Value, kvp => kvp.Key); } } } /// /// Specialization of ConversionContext for DomainConstraint BoolExpr /// internal sealed class DomainConstraintConversionContext: ConversionContext > { /// /// A map from domain variables to decision diagram variables. /// readonly Dictionary, int> _domainVariableToRobddVariableMap = new Dictionary , int>(); Dictionary > _inverseMap; /// /// Translates a domain constraint term to an N-ary DD vertex. /// internal override Vertex TranslateTermToVertex(TermExpr> term) { var range = term.Identifier.Range; var domainVariable = term.Identifier.Variable; var domain = domainVariable.Domain; if (range.All(element => !domain.Contains(element))) { // trivially false return Vertex.Zero; } if (domain.All(element => range.Contains(element))) { // trivially true return Vertex.One; } // determine assignments for this constraints (if the range contains a value in the domain, '1', else '0') Vertex[] children = domain.Select(element => range.Contains(element) ? Vertex.One : Vertex.Zero).ToArray(); // see if we know this variable int robddVariable; if (!_domainVariableToRobddVariableMap.TryGetValue(domainVariable, out robddVariable)) { robddVariable = Solver.CreateVariable(); _domainVariableToRobddVariableMap[domainVariable] = robddVariable; } // create a new vertex with the given assignments return Solver.CreateLeafVertex(robddVariable, children); } internal override IEnumerable >> GetSuccessors(Vertex vertex) { InitializeInverseMap(); var domainVariable = _inverseMap[vertex.Variable]; // since vertex children are ordinally aligned with domain, handle domain as array var domain = domainVariable.Domain.ToArray(); // foreach unique successor vertex, build up range Dictionary > vertexToRange = new Dictionary >(); for (int i = 0; i < vertex.Children.Length; i++) { Vertex successorVertex = vertex.Children[i]; Set range; if (!vertexToRange.TryGetValue(successorVertex, out range)) { range = new Set (domainVariable.Domain.Comparer); vertexToRange.Add(successorVertex, range); } range.Add(domain[i]); } foreach (var vertexRange in vertexToRange) { var successorVertex = vertexRange.Key; var range = vertexRange.Value; // construct a DomainConstraint including the given range var constraint = new DomainConstraint (domainVariable, range.MakeReadOnly()); var literal = new Literal >( new TermExpr >(constraint), true); yield return new LiteralVertexPair >(successorVertex, literal); } } private void InitializeInverseMap() { if (null == _inverseMap) { _inverseMap = _domainVariableToRobddVariableMap.ToDictionary(kvp => kvp.Value, kvp => kvp.Key); } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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