/** 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));
}
/** Model check a property. */
public Result check(Expression expr) throws PrismException {
Modules2PTA m2pta;
Result res;
String resultString;
long timer;
// Starting model checking
timer = System.currentTimeMillis();
// Check for system...endsystem - not supported yet
if (modulesFile.getSystemDefn() != null) {
throw new PrismException(
"The system...endsystem construct is not supported yet (try the digital clocks engine instead)");
}
// Translate ModulesFile object into a PTA object
mainLog.println("\nBuilding PTA...");
m2pta = new Modules2PTA(prism, modulesFile);
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 (try the digital clocks engine instead)",
e);
} else {
return e;
}
}
});
// Take a copy of property, since will modify
expr = expr.deepCopy();
// Remove property refs ands labels from property
expr = (Expression) expr.expandPropRefsAndLabels(propertiesFile, labelList);
// Evaluate constants in property (easier to do now)
expr = (Expression) expr.replaceConstants(constantValues);
// Also simplify expression to optimise model checking
expr = (Expression) expr.simplify();
// Do model checking
res = checkExpression(expr);
// Model checking complete
timer = System.currentTimeMillis() - timer;
mainLog.println("\nModel checking completed in " + (timer / 1000.0) + " secs.");
// Print result to log
resultString = "Result";
if (!("Result".equals(expr.getResultName())))
resultString += " (" + expr.getResultName().toLowerCase() + ")";
resultString += ": " + res;
mainLog.print("\n" + resultString + "\n");
// Return result
return res;
}
