Optimisation to CTMC transient probability computation for when time is zero.

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@73 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/prism/StochModelChecker.java

@@ -2023,7 +2023,13 @@ public class StochModelChecker implements ModelChecker
 		
 		// compute transient probabilities
 		try {
-			probs = computeTransientProbs(trans, init, time);
+			// special case: time = 0
+			if (time == 0.0) {
+				JDD.Ref(init);
+				probs = new StateProbsMTBDD(init, model);
+			} else {
+				probs = computeTransientProbs(trans, init, time);
+			}
 		}
 		catch (PrismException e) {
 			JDD.Deref(init);