/** Model check a P operator. */
private Result checkExpressionProb(ExpressionProb expr) throws PrismException {
boolean min;
ExpressionTemporal exprTemp;
Expression exprTarget;
BitSet targetLocs;
int timeBound;
boolean timeBoundStrict;
double prob;
// Check whether Pmin=? or Pmax=? (only two cases allowed)
if (expr.getProb() != null) {
throw new PrismException(
"PTA model checking currently only supports Pmin=? and Pmax=? properties (try the digital clocks engine instead)");
}
min = expr.getRelOp().equals("min=");
// Check this is a F path property (only case allowed at the moment)
if (!(expr.getExpression() instanceof ExpressionTemporal))
throw new PrismException(
"PTA model checking currently only supports the F path operator (try the digital clocks engine instead)");
exprTemp = (ExpressionTemporal) expr.getExpression();
if (exprTemp.getOperator() != ExpressionTemporal.P_F || !exprTemp.isSimplePathFormula())
throw new PrismException(
"PTA model checking currently only supports the F path operator (try the digital clocks engine instead)");
// Determine locations satisfying target
exprTarget = exprTemp.getOperand2();
targetLocs = checkLocationExpression(exprTarget);
mainLog.println(
"Target (" + exprTarget + ") satisfied by " + targetLocs.cardinality() + " locations.");
// mainLog.println(targetLocs);
// If there is a time bound, add a clock and encode this into target
if (exprTemp.hasBounds()) {
mainLog.println("Modifying PTA to encode time bound from property...");
// Get time bound info (is always of form <=T or <T)
timeBound = exprTemp.getUpperBound().evaluateInt(constantValues);
timeBoundStrict = exprTemp.upperBoundIsStrict();
// Modify PTA to include time bound; get new target
targetLocs = buildTimeBoundIntoPta(pta, targetLocs, timeBound, timeBoundStrict);
mainLog.println("New PTA: " + pta.infoString());
}
// Compute probability of reaching the set of target locations
prob = computeProbabilisticReachability(targetLocs, min);
// Return result
return new Result(new Double(prob));
}
/**
* Create a sampler for an expression (P=? or R=?). Expression should contain no
* constants/formula/etc. The model to which the property applies should also be specified.
*/
public static Sampler createSampler(Expression expr, ModulesFile mf) throws PrismException {
Sampler sampler = null;
// P=?
if (expr instanceof ExpressionProb) {
ExpressionProb propProb = (ExpressionProb) expr;
// Test whether this is a simple path formula (i.e. non-LTL)
if (propProb.getExpression().isSimplePathFormula()) {
sampler = createSamplerForProbPathPropertySimple(propProb.getExpression(), mf);
} else {
throw new PrismException("LTL-style path formulas are not supported by the simulator");
}
}
// R=?
else if (expr instanceof ExpressionReward) {
sampler = createSamplerForRewardProperty((ExpressionReward) expr, mf);
}
// Neither
else {
throw new PrismException("Can't create sampler for property \"" + expr + "\"");
}
return sampler;
}