Esempio n. 1
0
        protected void ProcessAssign(IExpression target, IExpression rhs, ref bool shouldDelete)
        {
            IVariableDeclaration ivd = Recognizer.GetVariableDeclaration(target);

            if (ivd == null)
            {
                return;
            }
            if (rhs is IArrayCreateExpression)
            {
                IArrayCreateExpression iace = (IArrayCreateExpression)rhs;
                bool zeroLength             = iace.Dimensions.All(dimExpr =>
                                                                  (dimExpr is ILiteralExpression) && ((ILiteralExpression)dimExpr).Value.Equals(0));
                if (!zeroLength && iace.Initializer == null)
                {
                    return; // variable will have assignments to elements
                }
            }
            bool firstTime = !variablesAssigned.Contains(ivd);

            variablesAssigned.Add(ivd);
            bool isInferred   = context.InputAttributes.Has <IsInferred>(ivd);
            bool isStochastic = CodeRecognizer.IsStochastic(context, ivd);

            if (!isStochastic)
            {
                return;
            }
            VariableInformation vi            = VariableInformation.GetVariableInformation(context, ivd);
            Containers          defContainers = context.InputAttributes.Get <Containers>(ivd);
            int        ancIndex = defContainers.GetMatchingAncestorIndex(context);
            Containers missing  = defContainers.GetContainersNotInContext(context, ancIndex);
            // definition of a stochastic variable
            IExpression lhs = target;

            if (lhs is IVariableDeclarationExpression)
            {
                lhs = Builder.VarRefExpr(ivd);
            }
            IExpression defExpr = lhs;

            if (firstTime && isStochastic)
            {
                // Create a ChannelInfo attribute for use by later transforms, e.g. MessageTransform
                ChannelInfo defChannel = ChannelInfo.DefChannel(vi);
                defChannel.decl = ivd;
                context.OutputAttributes.Set(ivd, defChannel);
            }
            bool       isDerived = context.InputAttributes.Has <DerivedVariable>(ivd);
            IAlgorithm algorithm = this.algorithmDefault;
            Algorithm  algAttr   = context.InputAttributes.Get <Algorithm>(ivd);

            if (algAttr != null)
            {
                algorithm = algAttr.algorithm;
            }
            if (algorithm is VariationalMessagePassing && ((VariationalMessagePassing)algorithm).UseDerivMessages && isDerived && firstTime)
            {
                vi.DefineAllIndexVars(context);
                IList <IStatement>   stmts     = Builder.StmtCollection();
                IVariableDeclaration derivDecl = vi.DeriveIndexedVariable(stmts, context, ivd.Name + "_deriv");
                context.OutputAttributes.Set(ivd, new DerivMessage(derivDecl));
                ChannelInfo derivChannel = ChannelInfo.DefChannel(vi);
                derivChannel.decl = derivDecl;
                context.OutputAttributes.Set(derivChannel.decl, derivChannel);
                context.OutputAttributes.Set(derivChannel.decl, new DescriptionAttribute("deriv of '" + ivd.Name + "'"));
                // Add the declarations
                stmts = Containers.WrapWithContainers(stmts, missing.outputs);
                context.AddStatementsBeforeAncestorIndex(ancIndex, stmts);
            }
            bool isPointEstimate = context.InputAttributes.Has <PointEstimate>(ivd);

            if (this.analysis.variablesExcludingVariableFactor.Contains(ivd))
            {
                this.variablesLackingVariableFactor.Add(ivd);
                // ivd will get a marginal channel in ConvertMethodInvoke
                useOfVariable[ivd] = ivd;
                return;
            }
            if (isDerived && !isInferred && !isPointEstimate)
            {
                return;
            }

            IExpression useExpr2 = null;

            if (firstTime)
            {
                // create marginal and use channels
                vi.DefineAllIndexVars(context);
                IList <IStatement> stmts = Builder.StmtCollection();

                CreateMarginalChannel(ivd, vi, stmts);
                if (isStochastic)
                {
                    CreateUseChannel(ivd, vi, stmts);
                    context.InputAttributes.Set(useOfVariable[ivd], defContainers);
                }

                // Add the declarations
                stmts = Containers.WrapWithContainers(stmts, missing.outputs);
                context.AddStatementsBeforeAncestorIndex(ancIndex, stmts);
            }
            if (isStochastic && !useOfVariable.ContainsKey(ivd))
            {
                Error("cannot find use channel of " + ivd);
                return;
            }
            IExpression  marginalExpr = Builder.ReplaceVariable(lhs, ivd, marginalOfVariable[ivd]);
            IExpression  useExpr      = isStochastic ? Builder.ReplaceVariable(lhs, ivd, useOfVariable[ivd]) : marginalExpr;
            InitialiseTo it           = context.InputAttributes.Get <InitialiseTo>(ivd);

            Type[] genArgs = new Type[] { defExpr.GetExpressionType() };
            if (rhs is IMethodInvokeExpression)
            {
                IMethodInvokeExpression imie = (IMethodInvokeExpression)rhs;
                if (Recognizer.IsStaticGenericMethod(imie, new Func <PlaceHolder, PlaceHolder>(Clone.Copy)) && ancIndex < context.InputStack.Count - 2)
                {
                    IExpression          arg  = imie.Arguments[0];
                    IVariableDeclaration ivd2 = Recognizer.GetVariableDeclaration(arg);
                    if (ivd2 != null && context.InputAttributes.Get <MarginalPrototype>(ivd) == context.InputAttributes.Get <MarginalPrototype>(ivd2))
                    {
                        // if a variable is a copy, use the original expression since it will give more precise dependencies.
                        defExpr      = arg;
                        shouldDelete = true;
                        bool makeClone = false;
                        if (makeClone)
                        {
                            VariableInformation         vi2      = VariableInformation.GetVariableInformation(context, ivd2);
                            IList <IStatement>          stmts    = Builder.StmtCollection();
                            List <IList <IExpression> > indices  = Recognizer.GetIndices(defExpr);
                            IVariableDeclaration        useDecl2 = vi2.DeriveIndexedVariable(stmts, context, ivd2.Name + "_use", indices);
                            useExpr2 = Builder.VarRefExpr(useDecl2);
                            Containers defContainers2 = context.InputAttributes.Get <Containers>(ivd2);
                            int        ancIndex2      = defContainers2.GetMatchingAncestorIndex(context);
                            Containers missing2       = defContainers2.GetContainersNotInContext(context, ancIndex2);
                            stmts = Containers.WrapWithContainers(stmts, missing2.outputs);
                            context.AddStatementsBeforeAncestorIndex(ancIndex2, stmts);
                            context.InputAttributes.Set(useDecl2, defContainers2);

                            // TODO: call CreateUseChannel
                            ChannelInfo usageChannel = ChannelInfo.UseChannel(vi2);
                            usageChannel.decl = useDecl2;
                            context.InputAttributes.CopyObjectAttributesTo <InitialiseTo>(vi.declaration, context.OutputAttributes, useDecl2);
                            context.InputAttributes.CopyObjectAttributesTo <DerivMessage>(vi.declaration, context.OutputAttributes, useDecl2);
                            context.OutputAttributes.Set(useDecl2, usageChannel);
                            //context.OutputAttributes.Set(useDecl2, new DescriptionAttribute("use of '" + ivd.Name + "'"));
                            context.OutputAttributes.Remove <InitialiseTo>(vi.declaration);

                            IExpression copyExpr = Builder.StaticGenericMethod(
                                new Func <PlaceHolder, PlaceHolder>(Clone.Copy), genArgs, useExpr2);
                            var copyStmt = Builder.AssignStmt(useExpr, copyExpr);
                            context.AddStatementAfterCurrent(copyStmt);
                        }
                    }
                }
            }

            // Add the variable factor
            IExpression variableFactorExpr;
            bool        isGateExitRandom = context.InputAttributes.Has <VariationalMessagePassing.GateExitRandomVariable>(ivd);

            if (isGateExitRandom)
            {
                variableFactorExpr = Builder.StaticGenericMethod(
                    new Models.FuncOut <PlaceHolder, PlaceHolder, PlaceHolder>(Gate.ExitingVariable),
                    genArgs, defExpr, marginalExpr);
            }
            else
            {
                Delegate d = algorithm.GetVariableFactor(isDerived, it != null);
                if (isPointEstimate)
                {
                    d = new Models.FuncOut <PlaceHolder, PlaceHolder, PlaceHolder>(Clone.VariablePoint);
                }
                if (it == null)
                {
                    variableFactorExpr = Builder.StaticGenericMethod(d, genArgs, defExpr, marginalExpr);
                }
                else
                {
                    IExpression initExpr = Builder.ReplaceExpression(lhs, Builder.VarRefExpr(ivd), it.initialMessagesExpression);
                    variableFactorExpr = Builder.StaticGenericMethod(d, genArgs, defExpr, initExpr, marginalExpr);
                }
            }
            context.InputAttributes.CopyObjectAttributesTo <GivePriorityTo>(ivd, context.OutputAttributes, variableFactorExpr);
            context.InputAttributes.CopyObjectAttributesTo <Algorithm>(ivd, context.OutputAttributes, variableFactorExpr);
            if (isStochastic)
            {
                context.OutputAttributes.Set(variableFactorExpr, new IsVariableFactor());
            }
            var assignStmt = Builder.AssignStmt(useExpr2 == null ? useExpr : useExpr2, variableFactorExpr);

            context.AddStatementAfterCurrent(assignStmt);
        }
Esempio n. 2
0
        /// <summary>
        /// Converts a variable declaration by creating definition, marginal and uses channel variables.
        /// </summary>
        protected override IExpression ConvertVariableDeclExpr(IVariableDeclarationExpression ivde)
        {
            IVariableDeclaration ivd = ivde.Variable;
            VariableInformation  vi  = VariableInformation.GetVariableInformation(context, ivd);

            // If the variable is deterministic, return
            bool isInferred = context.InputAttributes.Has <IsInferred>(ivd);

            if (!vi.IsStochastic)
            {
                return(ivde);
            }
            bool suppressVariableFactor = context.InputAttributes.Has <SuppressVariableFactor>(ivd);
            bool isDerived    = context.InputAttributes.Has <DerivedVariable>(ivd);
            bool isStochastic = vi.IsStochastic;
            int  useCount;

            ChannelAnalysisTransform.UsageInfo info;
            if (!analysis.usageInfo.TryGetValue(ivd, out info))
            {
                useCount = 0;
            }
            else
            {
                useCount = info.NumberOfUsesOld;
            }
            if (!(algorithm is Algorithms.GibbsSampling) && isStochastic && !suppressVariableFactor && (useCount <= 1) && !isInferred && isDerived)
            {
                // this is optional
                suppressVariableFactor = true;
                context.InputAttributes.Set(ivd, new SuppressVariableFactor());
            }
            context.InputAttributes.Remove <LoopContext>(ivd);
            context.InputAttributes.Set(ivd, new LoopContext(context));

            // Create variable-to-channel information for the variable.
            VariableToChannelInformation vtci = new VariableToChannelInformation();

            vtci.shareAllUses = (useCount <= 1);
            Context.InputAttributes.Set(ivd, vtci);

            // Create the definition channel
            vtci.defChannel      = ChannelInfo.DefChannel(vi);
            vtci.defChannel.decl = ivd;
            // Always create a variable factor for a stochastic variable
            if (isInferred || (isStochastic && !suppressVariableFactor))
            {
                vi.DefineAllIndexVars(context);
                IList <IStatement> stmts = Builder.StmtCollection();

                // Create marginal channel
                CreateMarginalChannel(vi, vtci, stmts);
                if (algorithm is GibbsSampling && ((GibbsSampling)algorithm).UseSideChannels)
                {
                    CreateSamplesChannel(vi, vtci, stmts);
                    CreateConditionalsChannel(vi, vtci, stmts);
                }
                else
                {
                    vtci.samplesChannel      = vtci.marginalChannel;
                    vtci.conditionalsChannel = vtci.marginalChannel;
                }
                if (isStochastic)
                {
                    // Create uses channel
                    CreateUsesChannel(vi, useCount, vtci, stmts);
                }

                //setAllGroupRoots(context, ivd, false);

                context.AddStatementsBeforeCurrent(stmts);

                // Append usageDepth indices to def/marginal/use expressions
                IExpression defExpr      = Builder.VarRefExpr(ivd);
                IExpression marginalExpr = Builder.VarRefExpr(vtci.marginalChannel.decl);
                IExpression countExpr    = Builder.LiteralExpr(useCount);

                // Add clone factor tying together all of the channels
                IMethodInvokeExpression variableFactorExpr;
                Type[] genArgs = new Type[] { vi.varType };
                if (algorithm is GibbsSampling && ((GibbsSampling)algorithm).UseSideChannels)
                {
                    GibbsSampling gs               = (GibbsSampling)algorithm;
                    IExpression   burnInExpr       = Builder.LiteralExpr(gs.BurnIn);
                    IExpression   thinExpr         = Builder.LiteralExpr(gs.Thin);
                    IExpression   samplesExpr      = Builder.VarRefExpr(vtci.samplesChannel.decl);
                    IExpression   conditionalsExpr = Builder.VarRefExpr(vtci.conditionalsChannel.decl);
                    if (isDerived)
                    {
                        Delegate d = new FuncOut3 <PlaceHolder, int, int, int, PlaceHolder, PlaceHolder, PlaceHolder, PlaceHolder[]>(Clone.ReplicateWithMarginalGibbs);
                        variableFactorExpr = Builder.StaticGenericMethod(d, genArgs, defExpr, countExpr, burnInExpr, thinExpr, marginalExpr, samplesExpr, conditionalsExpr);
                    }
                    else
                    {
                        Delegate d = new FuncOut3 <PlaceHolder, int, int, int, PlaceHolder, PlaceHolder, PlaceHolder, PlaceHolder[]>(Clone.UsesEqualDefGibbs);
                        variableFactorExpr = Builder.StaticGenericMethod(d, genArgs, defExpr, countExpr, burnInExpr, thinExpr, marginalExpr, samplesExpr, conditionalsExpr);
                    }
                }
                else
                {
                    Delegate d;
                    if (isDerived)
                    {
                        d = new FuncOut <PlaceHolder, int, PlaceHolder, PlaceHolder[]>(Clone.ReplicateWithMarginal <PlaceHolder>);
                    }
                    else
                    {
                        d = new FuncOut <PlaceHolder, int, PlaceHolder, PlaceHolder[]>(Clone.UsesEqualDef <PlaceHolder>);
                    }
                    variableFactorExpr = Builder.StaticGenericMethod(d, genArgs, defExpr, countExpr, marginalExpr);
                }
                if (isDerived)
                {
                    context.OutputAttributes.Set(variableFactorExpr, new DerivedVariable());            // used by Gibbs
                }
                // Mark this as a pseudo-factor
                context.OutputAttributes.Set(variableFactorExpr, new IsVariableFactor());
                if (useCount <= 1)
                {
                    context.OutputAttributes.Set(variableFactorExpr, new DivideMessages(false));
                }
                else
                {
                    context.InputAttributes.CopyObjectAttributesTo <DivideMessages>(ivd, context.OutputAttributes, variableFactorExpr);
                }
                context.InputAttributes.CopyObjectAttributesTo <GivePriorityTo>(ivd, context.OutputAttributes, variableFactorExpr);
                if (vtci.usageChannel != null)
                {
                    IExpression       usageExpr  = Builder.VarRefExpr(vtci.usageChannel.decl);
                    IAssignExpression assignExpr = Builder.AssignExpr(usageExpr, variableFactorExpr);
                    // Copy attributes across from input to output
                    Context.InputAttributes.CopyObjectAttributesTo <Algorithm>(ivd, context.OutputAttributes, assignExpr);
                    context.OutputAttributes.Remove <InitialiseTo>(ivd);
                    if (vi.ArrayDepth == 0)
                    {
                        // Insert the UsesEqualDef statement after the declaration.
                        // Note the variable will not have been defined yet.
                        context.AddStatementAfterCurrent(Builder.ExprStatement(assignExpr));
                    }
                    else
                    {
                        // For an array, the UsesEqualDef statement should be inserted after the array is allocated.
                        // Store the statement for later use by ConvertArrayCreate.
                        context.InputAttributes.Remove <LoopContext>(ivd);
                        context.InputAttributes.Set(ivd, new LoopContext(context));
                        context.InputAttributes.Remove <Containers>(ivd);
                        context.InputAttributes.Set(ivd, new Containers(context));
                        vtci.usesEqualDefsStatements = Builder.StmtCollection();
                        vtci.usesEqualDefsStatements.Add(Builder.ExprStatement(assignExpr));
                    }
                }
            }
            // These must be set after the above or they will be copied to the other channels
            if (isStochastic)
            {
                context.OutputAttributes.Set(ivd, vtci.defChannel);
            }
            if (!context.InputAttributes.Has <DescriptionAttribute>(vtci.defChannel.decl))
            {
                context.OutputAttributes.Set(vtci.defChannel.decl, new DescriptionAttribute("definition of '" + ivd.Name + "'"));
            }
            return(ivde);
        }
Esempio n. 3
0
        /// <summary>
        /// Converts a variable declaration by creating definition, marginal and uses channel variables.
        /// </summary>
        protected override IExpression ConvertVariableDeclExpr(IVariableDeclarationExpression ivde)
        {
            IVariableDeclaration ivd = ivde.Variable;
            VariableInformation  vi  = VariableInformation.GetVariableInformation(context, ivd);

            // If the variable is deterministic, return
            if (!vi.IsStochastic)
            {
                ProcessConstant(ivd);
                context.OutputAttributes.Set(ivd, new DescriptionAttribute("The constant '" + ivd.Name + "'"));
                return(ivde);
            }
            bool suppressVariableFactor = context.InputAttributes.Has <SuppressVariableFactor>(ivd);
            bool isDerived  = context.InputAttributes.Has <DerivedVariable>(ivd);
            bool isConstant = false;
            bool isInferred = context.InputAttributes.Has <IsInferred>(ivd);
            int  useCount;

            ChannelAnalysisTransform.UsageInfo info;
            if (!analysis.usageInfo.TryGetValue(ivd, out info))
            {
                useCount = 0;
            }
            else
            {
                useCount = info.NumberOfUsesOld;
            }
            if (!(algorithm is Algorithms.GibbsSampling) && !isConstant && !suppressVariableFactor && (useCount == 1) && !isInferred && isDerived)
            {
                // this is optional
                suppressVariableFactor = true;
                context.InputAttributes.Set(ivd, new SuppressVariableFactor());
            }
            context.InputAttributes.Remove <LoopContext>(ivd);
            context.InputAttributes.Set(ivd, new LoopContext(context));

            // Create variable-to-channel information for the variable.
            VariableToChannelInformation vtc = new VariableToChannelInformation();

            vtc.shareAllUses = (useCount == 1);
            Context.InputAttributes.Set(ivd, vtc);

            // Ensure the marginal prototype is set.
            MarginalPrototype mpa = Context.InputAttributes.Get <MarginalPrototype>(ivd);

            try
            {
                vi.SetMarginalPrototypeFromAttribute(mpa);
            }
            catch (ArgumentException ex)
            {
                Error(ex.Message);
            }

            // Create the definition channel
            vtc.defChannel      = ChannelInfo.DefChannel(vi);
            vtc.defChannel.decl = ivd;
            // Always create a variable factor for a stochastic variable
            if (!isConstant && !suppressVariableFactor)
            {
                vi.DefineAllIndexVars(context);
                IList <IStatement> stmts = Builder.StmtCollection();

                // Create marginal channel
                vtc.marginalChannel      = ChannelInfo.MarginalChannel(vi);
                vtc.marginalChannel.decl = vi.DeriveIndexedVariable(stmts, context, vi.Name + "_marginal");
                context.InputAttributes.CopyObjectAttributesTo <InitialiseTo>(vi.declaration, context.OutputAttributes, vtc.marginalChannel.decl);
                context.OutputAttributes.Set(vtc.marginalChannel.decl, vtc.marginalChannel);
                context.OutputAttributes.Set(vtc.marginalChannel.decl, new DescriptionAttribute("marginal of '" + ivd.Name + "'"));
                SetMarginalPrototype(vtc.marginalChannel.decl);
                if (algorithm is GibbsSampling && ((GibbsSampling)algorithm).UseSideChannels)
                {
                    Type marginalType = MessageTransform.GetDistributionType(vi.varType, vi.InnermostElementType,
                                                                             vi.marginalPrototypeExpression.GetExpressionType(), true);
                    Type domainType = ivd.VariableType.DotNetType;

                    vtc.samplesChannel      = ChannelInfo.MarginalChannel(vi);
                    vtc.samplesChannel.decl = vi.DeriveIndexedVariable(stmts, context, vi.Name + "_samples");
                    context.OutputAttributes.Remove <InitialiseTo>(vtc.samplesChannel.decl);
                    context.OutputAttributes.Set(vtc.samplesChannel.decl, vtc.samplesChannel);
                    context.OutputAttributes.Set(vtc.samplesChannel.decl, new DescriptionAttribute("samples of '" + ivd.Name + "'"));
                    Type                samplesType = typeof(List <>).MakeGenericType(domainType);
                    IExpression         samples_mpe = Builder.NewObject(samplesType);
                    VariableInformation samples_vi  = VariableInformation.GetVariableInformation(context, vtc.samplesChannel.decl);
                    samples_vi.marginalPrototypeExpression = samples_mpe;

                    vtc.conditionalsChannel      = ChannelInfo.MarginalChannel(vi);
                    vtc.conditionalsChannel.decl = vi.DeriveIndexedVariable(stmts, context, vi.Name + "_conditionals");
                    context.OutputAttributes.Remove <InitialiseTo>(vtc.conditionalsChannel.decl);
                    context.OutputAttributes.Set(vtc.conditionalsChannel.decl, vtc.conditionalsChannel);
                    context.OutputAttributes.Set(vtc.conditionalsChannel.decl, new DescriptionAttribute("conditionals of '" + ivd.Name + "'"));
                    Type                conditionalsType = typeof(List <>).MakeGenericType(marginalType);
                    IExpression         conditionals_mpe = Builder.NewObject(conditionalsType);
                    VariableInformation conditionals_vi  = VariableInformation.GetVariableInformation(context, vtc.conditionalsChannel.decl);
                    conditionals_vi.marginalPrototypeExpression = conditionals_mpe;
                }
                else
                {
                    vtc.samplesChannel      = vtc.marginalChannel;
                    vtc.conditionalsChannel = vtc.marginalChannel;
                }

                // Create uses channel
                vtc.usageChannel      = ChannelInfo.UseChannel(vi);
                vtc.usageChannel.decl = vi.DeriveArrayVariable(stmts, context, vi.Name + "_uses", Builder.LiteralExpr(useCount), Builder.VarDecl("_ind", typeof(int)), useLiteralIndices: true);
                context.InputAttributes.CopyObjectAttributesTo <InitialiseTo>(vi.declaration, context.OutputAttributes, vtc.usageChannel.decl);
                context.OutputAttributes.Set(vtc.usageChannel.decl, vtc.usageChannel);
                context.OutputAttributes.Set(vtc.usageChannel.decl, new DescriptionAttribute("uses of '" + ivd.Name + "'"));
                SetMarginalPrototype(vtc.usageChannel.decl);

                //setAllGroupRoots(context, ivd, false);

                context.AddStatementsBeforeCurrent(stmts);

                // Append usageDepth indices to def/marginal/use expressions
                IExpression defExpr      = Builder.VarRefExpr(ivd);
                IExpression marginalExpr = Builder.VarRefExpr(vtc.marginalChannel.decl);
                IExpression usageExpr    = Builder.VarRefExpr(vtc.usageChannel.decl);
                IExpression countExpr    = Builder.LiteralExpr(useCount);

                // Add clone factor tying together all of the channels
                IMethodInvokeExpression usesEqualDefExpression;
                Type[] genArgs = new Type[] { vi.varType };
                if (algorithm is GibbsSampling && ((GibbsSampling)algorithm).UseSideChannels)
                {
                    GibbsSampling gs               = (GibbsSampling)algorithm;
                    IExpression   burnInExpr       = Builder.LiteralExpr(gs.BurnIn);
                    IExpression   thinExpr         = Builder.LiteralExpr(gs.Thin);
                    IExpression   samplesExpr      = Builder.VarRefExpr(vtc.samplesChannel.decl);
                    IExpression   conditionalsExpr = Builder.VarRefExpr(vtc.conditionalsChannel.decl);
                    if (isDerived)
                    {
                        Delegate d = new FuncOut3 <PlaceHolder, int, int, int, PlaceHolder, PlaceHolder, PlaceHolder, PlaceHolder[]>(Factor.ReplicateWithMarginalGibbs);
                        usesEqualDefExpression = Builder.StaticGenericMethod(d, genArgs, defExpr, countExpr, burnInExpr, thinExpr, marginalExpr, samplesExpr, conditionalsExpr);
                    }
                    else
                    {
                        Delegate d = new FuncOut3 <PlaceHolder, int, int, int, PlaceHolder, PlaceHolder, PlaceHolder, PlaceHolder[]>(Factor.UsesEqualDefGibbs);
                        usesEqualDefExpression = Builder.StaticGenericMethod(d, genArgs, defExpr, countExpr, burnInExpr, thinExpr, marginalExpr, samplesExpr, conditionalsExpr);
                    }
                }
                else
                {
                    Delegate d;
                    if (isDerived)
                    {
                        d = new FuncOut <PlaceHolder, int, PlaceHolder, PlaceHolder[]>(Factor.ReplicateWithMarginal <PlaceHolder>);
                    }
                    else
                    {
                        d = new FuncOut <PlaceHolder, int, PlaceHolder, PlaceHolder[]>(Factor.UsesEqualDef <PlaceHolder>);
                    }
                    usesEqualDefExpression = Builder.StaticGenericMethod(d, genArgs, defExpr, countExpr, marginalExpr);
                }
                if (isDerived)
                {
                    context.OutputAttributes.Set(usesEqualDefExpression, new DerivedVariable());            // used by Gibbs
                }
                // Mark this as a pseudo-factor
                context.OutputAttributes.Set(usesEqualDefExpression, new IsVariableFactor());
                if (useCount == 1)
                {
                    context.OutputAttributes.Set(usesEqualDefExpression, new DivideMessages(false));
                }
                else
                {
                    context.InputAttributes.CopyObjectAttributesTo <DivideMessages>(ivd, context.OutputAttributes, usesEqualDefExpression);
                }
                context.InputAttributes.CopyObjectAttributesTo <GivePriorityTo>(ivd, context.OutputAttributes, usesEqualDefExpression);
                IAssignExpression assignExpr = Builder.AssignExpr(usageExpr, usesEqualDefExpression);

                // Copy attributes across from input to output
                Context.InputAttributes.CopyObjectAttributesTo <Algorithm>(ivd, context.OutputAttributes, assignExpr);
                context.OutputAttributes.Remove <InitialiseTo>(ivd);
                if (vi.ArrayDepth == 0)
                {
                    // Insert the UsesEqualDef statement after the declaration.
                    // Note the variable will not have been defined yet.
                    context.AddStatementAfterCurrent(Builder.ExprStatement(assignExpr));
                }
                else
                {
                    // For an array, the UsesEqualDef statement should be inserted after the array is allocated.
                    // Store the statement for later use by ConvertArrayCreate.
                    context.InputAttributes.Remove <LoopContext>(ivd);
                    context.InputAttributes.Set(ivd, new LoopContext(context));
                    context.InputAttributes.Remove <Containers>(ivd);
                    context.InputAttributes.Set(ivd, new Containers(context));
                    vtc.usesEqualDefsStatements = Builder.StmtCollection();
                    vtc.usesEqualDefsStatements.Add(Builder.ExprStatement(assignExpr));
                }
            }
            // These must be set after the above or they will be copied to the other channels
            context.OutputAttributes.Set(ivd, vtc.defChannel);
            context.OutputAttributes.Set(vtc.defChannel.decl, new DescriptionAttribute("definition of '" + ivd.Name + "'"));
            return(ivde);
        }