Better property checks for PTAs, including new computation of prob operator nesting. Better handling of labels in PTA model checker.

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@2176 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/parser/ast/ASTElement.java

@@ -410,6 +410,16 @@ public abstract class ASTElement
 		return (ASTElement) accept(visitor);
 	}
 
+	/**
+	 * Compute (maximum) number of nested probabilistic operators (P, S, R).
+	 */
+	public int computeProbNesting() throws PrismLangException
+	{
+		ComputeProbNesting visitor = new ComputeProbNesting();
+		accept(visitor);
+		return visitor.getMaxNesting();
+	}
+
 	/**
 	 * Convert to string showing tree representation.
 	 */

prism/src/parser/visitor/ComputeProbNesting.java

@@ -0,0 +1,84 @@
+//==============================================================================
+//	
+//	Copyright (c) 2002-
+//	Authors:
+//	* Dave Parker <david.parker@comlab.ox.ac.uk> (University of Oxford)
+//	
+//------------------------------------------------------------------------------
+//	
+//	This file is part of PRISM.
+//	
+//	PRISM is free software; you can redistribute it and/or modify
+//	it under the terms of the GNU General Public License as published by
+//	the Free Software Foundation; either version 2 of the License, or
+//	(at your option) any later version.
+//	
+//	PRISM is distributed in the hope that it will be useful,
+//	but WITHOUT ANY WARRANTY; without even the implied warranty of
+//	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//	GNU General Public License for more details.
+//	
+//	You should have received a copy of the GNU General Public License
+//	along with PRISM; if not, write to the Free Software Foundation,
+//	Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+//	
+//==============================================================================
+
+package parser.visitor;
+
+import parser.ast.*;
+import prism.PrismLangException;
+
+/**
+ * Compute (maximum) number of nested probabilistic operators (P, S, R).
+ */
+public class ComputeProbNesting extends ASTTraverse
+{
+	private int currentNesting;
+	private int maxNesting;
+	
+	public ComputeProbNesting()
+	{
+		currentNesting = 0;
+		maxNesting = 0;
+	}
+
+	public int getMaxNesting()
+	{
+		return maxNesting;
+	}
+	
+	public void visitPre(ExpressionProb e) throws PrismLangException
+	{
+		currentNesting++;
+		maxNesting = Math.max(maxNesting, currentNesting);
+	}
+
+	public void visitPost(ExpressionProb e) throws PrismLangException
+	{
+		currentNesting--;
+	}
+
+	public void visitPre(ExpressionReward e) throws PrismLangException
+	{
+		currentNesting++;
+		maxNesting = Math.max(maxNesting, currentNesting);
+	}
+
+	public void visitPost(ExpressionReward e) throws PrismLangException
+	{
+		currentNesting--;
+	}
+
+	public void visitPre(ExpressionSS e) throws PrismLangException
+	{
+		currentNesting++;
+		maxNesting = Math.max(maxNesting, currentNesting);
+	}
+	
+	public void visitPost(ExpressionSS e) throws PrismLangException
+	{
+		currentNesting--;
+	}
+}
+

prism/src/pta/DigitalClocks.java

@@ -119,17 +119,14 @@ public class DigitalClocks
 			{
 				if (e.getOperand1().getType() instanceof TypeClock) {
 					if (e.getOperand2().getType() instanceof TypeClock) {
-						throw new PrismLangException(
-								"Diagonal clock constraints are not allowed when using the digital clocks method", e);
+						throw new PrismLangException("Diagonal clock constraints are not allowed when using the digital clocks method", e);
 					} else {
 						if (e.getOperator() == ExpressionBinaryOp.GT || e.getOperator() == ExpressionBinaryOp.LT)
-							throw new PrismLangException(
-									"Strict clock constraints are not allowed when using the digital clocks method", e);
+							throw new PrismLangException("Strict clock constraints are not allowed when using the digital clocks method", e);
 					}
 				} else if (e.getOperand2().getType() instanceof TypeClock) {
 					if (e.getOperator() == ExpressionBinaryOp.GT || e.getOperator() == ExpressionBinaryOp.LT)
-						throw new PrismLangException(
-								"Strict clock constraints are not allowed when using the digital clocks method", e);
+						throw new PrismLangException("Strict clock constraints are not allowed when using the digital clocks method", e);
 				}
 			}
 		};
@@ -137,6 +134,14 @@ public class DigitalClocks
 		if (propertiesFile != null)
 			propertiesFile.accept(astt);
 
+		// Check that there are no nested probabilistic operators
+		// TODO: should be checking on individual properties really 
+		if (propertiesFile != null) {
+			if (propertiesFile.computeProbNesting() > 1) {
+				throw new PrismLangException("Nested P operators are not allowed when using the digital clocks method");
+			}
+		}
+
 		// Choose a new action label to represent time
 		timeAction = "time";
 		while (modulesFile.getSynchs().contains(timeAction)) {
@@ -165,8 +170,7 @@ public class DigitalClocks
 				if (e.getDeclType() instanceof DeclarationClock) {
 					int cMax = cci.getScaledClockMax(e.getName());
 					if (cMax < 0)
-						throw new PrismLangException("Clock " + e.getName()
-								+ " is unbounded since there are no references to it in the model");
+						throw new PrismLangException("Clock " + e.getName() + " is unbounded since there are no references to it in the model");
 					DeclarationType declType = new DeclarationInt(Expression.Int(0), Expression.Int(cMax + 1));
 					Declaration decl = new Declaration(e.getName(), declType);
 					return decl;
@@ -281,8 +285,7 @@ public class DigitalClocks
 				continue;
 			// TODO: handle this case
 			if (rs.getNumTransItems() > 0)
-				throw new PrismLangException(
-						"Translation of reward structures with both state/transition items is not yet supported");
+				throw new PrismLangException("Translation of reward structures with both state/transition items is not yet supported");
 			n = rs.getNumItems();
 			for (i = 0; i < n; i++) {
 				RewardStructItem rsi = rs.getRewardStructItem(i);

prism/src/pta/PTAModelChecker.java

@@ -31,7 +31,9 @@ import java.util.*;
 import parser.*;
 import parser.ast.*;
 import parser.type.*;
+import parser.visitor.ASTTraverseModify;
 import prism.*;
+import simulator.sampler.Sampler;
 import explicit.*;
 
 /**
@@ -49,7 +51,7 @@ public class PTAModelChecker
 	private PropertiesFile propertiesFile;
 	// Constants from model
 	private Values constantValues;
-	// Label list
+	// Label list (combined: model/properties file)
 	private LabelList labelList;
 	// PTA
 	private PTA pta;
@@ -115,8 +117,28 @@ public class PTAModelChecker
 		pta = m2pta.translate();
 		mainLog.println("\nPTA: " + pta.infoString());
 
+		// Check for references to clocks - not allowed (yet)
+		// (do this before modifications below for better error reporting)
+		expr.accept(new ASTTraverseModify()
+		{
+			public Object visit(ExpressionVar e) throws PrismLangException
+			{
+				if (e.getType() instanceof TypeClock) {
+					throw new PrismLangException("Properties cannot contain references to clocks", e);
+				} else {
+					return e;
+				}
+			}
+		});
+		
+		// Take a copy of property, since will modify
+		expr = expr.deepCopy();
+		// Remove labels from property, using combined label list 
+		expr = (Expression) expr.expandLabels(labelList);
 		// Evaluate constants in property (easier to do now)
-		expr = (Expression) expr.deepCopy().replaceConstants(constantValues);
+		expr = (Expression) expr.replaceConstants(constantValues);
+		// Also simplify expression to optimise model checking
+		expr = (Expression) expr.simplify();
 
 		// Do model checking
 		res = checkExpression(expr);
@@ -177,9 +199,9 @@ public class PTAModelChecker
 		if (!(expr.getExpression() instanceof ExpressionTemporal))
 			throw new PrismException("PTA model checking currently only supports the F path operator");
 		exprTemp = (ExpressionTemporal) expr.getExpression();
-		if (exprTemp.getOperator() != ExpressionTemporal.P_F)
+		if (exprTemp.getOperator() != ExpressionTemporal.P_F || !exprTemp.isSimplePathFormula())
 			throw new PrismException("PTA model checking currently only supports the F path operator");
-
+		
 		// Determine locations satisfying target
 		exprTarget = exprTemp.getOperand2();
 		targetLocs = checkLocationExpression(exprTarget);
@@ -314,6 +336,7 @@ public class PTAModelChecker
 	/**
 	 * Determine which locations in the PTA satisfy a (Boolean) expression.
 	 * Note: This is rather inefficiently at the moment.
+	 * TODO: potentially use explicit.StateMC on dummy model eventually
 	 */
 	private BitSet checkLocationExpression(Expression expr) throws PrismException
 	{
@@ -321,6 +344,7 @@ public class PTAModelChecker
 		BitSet res;
 
 		// Labels - expand and recurse
+		// (note: currently not used - these are expanded earlier)
 		if (expr instanceof ExpressionLabel) {
 			ExpressionLabel exprLabel = (ExpressionLabel) expr;
 			if (exprLabel.getName().equals("deadlock"))

prism/src/simulator/SimulatorEngine.java

@@ -33,7 +33,6 @@ import simulator.sampler.*;
 import parser.*;
 import parser.ast.*;
 import parser.type.*;
-import parser.visitor.ASTTraverse;
 import prism.*;
 
 /**
@@ -1081,41 +1080,20 @@ public class SimulatorEngine
 	{
 		// Simulator can only be applied to P=? or R=? properties
 		boolean ok = true;
-		Expression expr = null;
 		if (!(prop instanceof ExpressionProb || prop instanceof ExpressionReward))
 			ok = false;
 		else if (prop instanceof ExpressionProb) {
 			if ((((ExpressionProb) prop).getProb() != null))
 				ok = false;
-			expr = ((ExpressionProb) prop).getExpression();
 		} else if (prop instanceof ExpressionReward) {
 			if ((((ExpressionReward) prop).getReward() != null))
 				ok = false;
-			expr = ((ExpressionReward) prop).getExpression();
 		}
 		if (!ok)
 			throw new PrismException("Simulator can only handle P=? or R=? properties");
 
 		// Check that there are no nested probabilistic operators
-		try {
-			expr.accept(new ASTTraverse()
-			{
-				public void visitPre(ExpressionProb e) throws PrismLangException
-				{
-					throw new PrismLangException("");
-				}
-
-				public void visitPre(ExpressionReward e) throws PrismLangException
-				{
-					throw new PrismLangException("");
-				}
-
-				public void visitPre(ExpressionSS e) throws PrismLangException
-				{
-					throw new PrismLangException("");
-				}
-			});
-		} catch (PrismLangException e) {
+		if (prop.computeProbNesting() > 1) {
 			throw new PrismException("Simulator cannot handle nested P, R or S operators");
 		}
 	}