param/exact: warn if some probability/rate is zero in an update

The transitions are explored twice during model construction, once
to find the reachable states and the second time to actually build
the transition structure of the model. We suppress the warning
in the first pass so that it does not appear twice.


git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@11656 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/param/ModelBuilder.java

@@ -322,7 +322,7 @@ public final class ModelBuilder extends PrismComponent
 
 		while (!explore.isEmpty()) {
 			state = explore.removeFirst();
-			TransitionList tranlist = engine.calculateTransitions(state);
+			TransitionList tranlist = engine.calculateTransitions(state, true);  // Suppress warnings
 			int numChoices = tranlist.getNumChoices();
 			if (isNonDet) {
 				numTotalChoices += numChoices;
@@ -394,7 +394,7 @@ public final class ModelBuilder extends PrismComponent
 		model.addInitialState(permut[0]);
 		int stateNr = 0;
 		for (State state : statesList) {
-			TransitionList tranlist = engine.calculateTransitions(state);
+			TransitionList tranlist = engine.calculateTransitions(state, false);
 			int numChoices = tranlist.getNumChoices();
 
 			boolean computeSumOut = !isNonDet;

prism/src/param/SymbolicEngine.java

@@ -70,6 +70,9 @@ public class SymbolicEngine
 	protected ModelBuilder modelBuilder;
 	protected FunctionFactory functionFactory;
 
+	//  flag that suppresses warnings during calculateTransitions
+	private boolean noWarnings = false;
+
 	public SymbolicEngine(ModulesFile modulesFile, ModelBuilder modelBuilder, FunctionFactory functionFactory)
 	{
 		this.modelBuilder = modelBuilder;
@@ -137,12 +140,14 @@ public class SymbolicEngine
 		}
 	}
 	
-	public TransitionList calculateTransitions(State state) throws PrismException
+	public TransitionList calculateTransitions(State state, boolean noWarnings) throws PrismException
 	{
 		List<ChoiceListFlexi> chs;
 		int i, j, k, l, n, count;
 		TransitionList transitionList = new TransitionList();
 
+		this.noWarnings = noWarnings;
+
 		// Clear lists/bitsets
 		transitionList.clear();
 		for (i = 0; i < numModules; i++) {
@@ -295,6 +300,8 @@ public class SymbolicEngine
 				Function pFn = modelBuilder.expr2function(functionFactory, p);
 				if (pFn.isZero()) {
 					// function for probability / rate is zero, don't add the corresponding transition
+					if (!noWarnings)
+						modelBuilder.getLog().printWarning("Update has zero " + (modelType.continuousTime() ? "rate" : "probability") + " (" + p + (p.hasPosition() ? ", " + p.getBeginString() : "") +")");
 					continue;
 				}
 				ch.add(pFn, list);