Refactor (symbolic) steady-state computation.

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@5614 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/prism/ProbModelChecker.java

@@ -1620,17 +1620,19 @@ public class ProbModelChecker extends NonProbModelChecker
 	 */
 	public StateValues computeSteadyStateProbs(JDDNode tr, StateValues initDist) throws PrismException
 	{
-		// bscc stuff
-		Vector<JDDNode> vectBSCCs;
-		JDDNode notInBSCCs;
-		// mtbdd stuff
-		JDDNode start, bscc;
-		// other stuff
+		// BSCC stuff
+		Vector<JDDNode> vectBSCCs = null;
+		JDDNode notInBSCCs = null;
+		// MTBDD stuff
+		JDDNode start = null, bscc;
+		// Other stuff
 		StateValues probs = null, solnProbs = null;
 		double probBSCCs[];
-		int numBSCCs, allInOneBSCC;
+		int numBSCCs = 0, allInOneBSCC;
 
-		// compute bottom strongly connected components (bsccs)
+		try {
+
+			// Compute bottom strongly connected components (bsccs)
 			if (bsccComp) {
 				SCCComputer sccComputer = prism.getSCCComputer(model);
 				sccComputer.computeBSCCs();
@@ -1638,7 +1640,7 @@ public class ProbModelChecker extends NonProbModelChecker
 				notInBSCCs = sccComputer.getNotInBSCCs();
 				numBSCCs = vectBSCCs.size();
 			}
-		// unless we've been told to skip it
+			// Unless we've been told to skip it
 			else {
 				mainLog.println("\nSkipping BSCC computation...");
 				vectBSCCs = new Vector<JDDNode>();
@@ -1659,31 +1661,18 @@ public class ProbModelChecker extends NonProbModelChecker
 				}
 			}
 
-		// if all initial states are in a single bscc, it's easy...
+			// If all initial states are in a single BSCC, it's easy...
+			// Just compute steady-state probabilities for the BSCC
 			if (allInOneBSCC != -1) {
-
 				mainLog.println("\nInitial states all in one BSCC (so no reachability probabilities computed)");
-
-			// get bscc
 				bscc = vectBSCCs.elementAt(allInOneBSCC);
-
-			// compute steady-state probabilities for the bscc
-			try {
 				solnProbs = computeSteadyStateProbsForBSCC(trans, bscc);
-			} catch (PrismException e) {
-				JDD.Deref(start);
-				for (int b = 0; b < numBSCCs; b++) {
-					JDD.Deref(vectBSCCs.elementAt(b));
-				}
-				JDD.Deref(notInBSCCs);
-				throw e;
-			}
 			}
 
-		// otherwise have to consider all the bsccs
+			// Otherwise, have to consider all the BSCCs
 			else {
 
-			// initialise total probabilities vector
+				// Initialise total probabilities vector
 				switch (engine) {
 				case Prism.MTBDD:
 					solnProbs = new StateValuesMTBDD(JDD.Constant(0), model);
@@ -1696,78 +1685,62 @@ public class ProbModelChecker extends NonProbModelChecker
 					break;
 				}
 
-			// compute prob of reaching each bscc from initial state
+				// Compute prob of reaching each BSCC from initial state
 				probBSCCs = new double[numBSCCs];
 				for (int b = 0; b < numBSCCs; b++) {
-
 					mainLog.println("\nComputing probability of reaching BSCC " + (b + 1));
-
-				// get bscc
 					bscc = vectBSCCs.elementAt(b);
-
-				// compute probabilities
-				try {
+					// Compute probabilities
 					probs = computeUntilProbs(trans, trans01, notInBSCCs, bscc);
-				} catch (PrismException e) {
-					JDD.Deref(start);
-					for (b = 0; b < numBSCCs; b++) {
-						JDD.Deref(vectBSCCs.elementAt(b));
-					}
-					JDD.Deref(notInBSCCs);
-					solnProbs.clear();
-					throw e;
-				}
-
-				// compute probability of reaching BSCC, which is dot product of
+					// Compute probability of reaching BSCC, which is dot product of
 					// vectors for initial distribution and probabilities of reaching it
 					probBSCCs[b] = probs.dotProduct(initDist);
 					mainLog.print("\nProbability of reaching BSCC " + (b + 1) + ": " + probBSCCs[b] + "\n");
-
-				// free vector
+					// Free vector
 					probs.clear();
 				}
 
-			// compute steady-state for each bscc
+				// Compute steady-state probs for each BSCC
 				for (int b = 0; b < numBSCCs; b++) {
-
 					mainLog.println("\nComputing steady-state probabilities for BSCC " + (b + 1));
-
-				// get bscc
 					bscc = vectBSCCs.elementAt(b);
-
-				// compute steady-state probabilities for the bscc
-				try {
+					// Compute steady-state probabilities for the BSCC
 					probs = computeSteadyStateProbsForBSCC(trans, bscc);
-				} catch (PrismException e) {
-					JDD.Deref(start);
-					for (b = 0; b < numBSCCs; b++) {
-						JDD.Deref(vectBSCCs.elementAt(b));
-					}
-					JDD.Deref(notInBSCCs);
-					solnProbs.clear();
-					throw e;
-				}
-
-				// print out probabilities
+					// Print out probabilities
 					if (verbose) {
 						mainLog.print("\nBSCC " + (b + 1) + " Steady-State Probabilities: \n");
 						probs.print(mainLog);
 					}
-
-				// times by bscc reach prob, add to total
+					// Multiply by BSCC reach prob, add to total
 					probs.timesConstant(probBSCCs[b]);
 					solnProbs.add(probs);
-
-				// free vector
+					// Free vector
 					probs.clear();
 				}
 			}
+		} catch (PrismException e) {
+			// Tidy up and pass on the exception
+			if (start != null)
+				JDD.Deref(start);
+			for (int b = 0; b < numBSCCs; b++) {
+				if (vectBSCCs.elementAt(b) != null)
+					JDD.Deref(vectBSCCs.elementAt(b));
+			}
+			if (start != notInBSCCs)
+				JDD.Deref(notInBSCCs);
+			if (solnProbs != null)
+				solnProbs.clear();
+			throw e;
+		}
 
-		// derefs
+		// Tidy up
+		if (start != null)
 			JDD.Deref(start);
 		for (int b = 0; b < numBSCCs; b++) {
+			if (vectBSCCs.elementAt(b) != null)
 				JDD.Deref(vectBSCCs.elementAt(b));
 		}
+		if (start != notInBSCCs)
 			JDD.Deref(notInBSCCs);
 
 		return solnProbs;