/// <summary>
/// Computes the minimal critical sets for the <paramref name="hazard" />.
/// </summary>
/// <param name="createModel">The creator for the model that should be checked.</param>
/// <param name="hazard">The hazard the minimal critical sets should be computed for.</param>
/// <param name="maxCardinality">
/// The maximum cardinality of the fault sets that should be checked. By default, all minimal
/// critical fault sets are determined.
/// </param>
public SafetyAnalysisResults <TExecutableModel> ComputeMinimalCriticalSets(CoupledExecutableModelCreator <TExecutableModel> createModel, Formula hazard, int maxCardinality = Int32.MaxValue)
{
Requires.NotNull(createModel, nameof(createModel));
Requires.NotNull(hazard, nameof(hazard));
ConsoleHelpers.WriteLine("Running Deductive Cause Consequence Analysis.");
var heuristicWatch = new Stopwatch();
var stopwatch = new Stopwatch();
stopwatch.Start();
var allFaults = createModel.FaultsInBaseModel;
FaultSet.CheckFaultCount(allFaults.Length);
var forcedFaults = allFaults.Where(fault => fault.Activation == Activation.Forced).ToArray();
var suppressedFaults = allFaults.Where(fault => fault.Activation == Activation.Suppressed).ToArray();
var nondeterministicFaults = allFaults.Where(fault => fault.Activation == Activation.Nondeterministic).ToArray();
var nonSuppressedFaults = allFaults.Where(fault => fault.Activation != Activation.Suppressed).ToArray();
ConsoleHelpers.WriteLine();
ConsoleHelpers.WriteLine($"Of the {allFaults.Length} faults contained in the model,");
ConsoleHelpers.WriteLine($" {suppressedFaults.Length} faults are suppressed,");
ConsoleHelpers.WriteLine($" {forcedFaults.Length} faults are forced, and");
ConsoleHelpers.WriteLine($" {nondeterministicFaults.Length} faults are nondeterministically activated.");
ConsoleHelpers.WriteLine();
_suppressedSet = new FaultSet(suppressedFaults);
_forcedSet = new FaultSet(forcedFaults);
var isComplete = true;
// Remove information from previous analyses
Reset(createModel.FaultsInBaseModel);
// Initialize the backend, the model, and the analysis results
switch (Backend)
{
case SafetyAnalysisBackend.FaultOptimizedOnTheFly:
_backend = new FaultOptimizationBackend <TExecutableModel>();
break;
case SafetyAnalysisBackend.FaultOptimizedStateGraph:
_backend = new StateGraphBackend <TExecutableModel>();
break;
default:
throw new ArgumentOutOfRangeException();
}
_backend.Output = Output;
_backend.InitializeModel(Configuration, createModel, hazard);
_results = new SafetyAnalysisResults <TExecutableModel>(createModel, hazard, suppressedFaults, forcedFaults, Heuristics, FaultActivationBehavior);
// Remember all safe sets of current cardinality - we need them to generate the next power set level
var currentSafe = new HashSet <FaultSet>();
// We check fault sets by increasing cardinality; this is, we check the empty set first, then
// all singleton sets, then all sets with two elements, etc. We don't check sets that we
// know are going to be critical sets due to monotonicity
for (var cardinality = 0; cardinality <= nonSuppressedFaults.Length; ++cardinality)
{
// Generate the sets for the current level that we'll have to check
var sets = GeneratePowerSetLevel(cardinality, nonSuppressedFaults, currentSafe);
currentSafe.Clear();
// Remove all sets that conflict with the forced or suppressed faults; these sets are considered to be safe.
// If no sets remain, skip to the next level
sets = RemoveInvalidSets(sets, currentSafe);
if (sets.Count == 0)
{
continue;
}
// Abort if we've exceeded the maximum fault set cardinality; doing the check here allows us
// to report the analysis as complete if the maximum cardinality is never reached
if (cardinality > maxCardinality)
{
isComplete = false;
break;
}
if (cardinality == 0)
{
ConsoleHelpers.WriteLine("Checking the empty fault set...");
}
else
{
ConsoleHelpers.WriteLine($"Checking {sets.Count} sets of cardinality {cardinality}...");
}
// use heuristics
var setsToCheck = new LinkedList <FaultSet>(sets);
foreach (var heuristic in Heuristics)
{
var count = setsToCheck.Count;
heuristicWatch.Restart();
heuristic.Augment((uint)cardinality, setsToCheck);
count = setsToCheck.Count - count;
if (count > 0)
{
ConsoleHelpers.WriteLine($" {heuristic.GetType().Name} made {count} suggestions in {heuristicWatch.Elapsed.TotalMilliseconds}ms.");
}
}
// We have to check each set - heuristics may add further during the loop
while (setsToCheck.Count > 0)
{
var set = setsToCheck.First.Value;
var isCurrentLevel = sets.Remove(set); // returns true if set was actually contained
setsToCheck.RemoveFirst();
// for current level, we already know the set is valid
var isValid = isCurrentLevel || IsValid(set);
// the set is invalid if it exceeds the maximum cardinality level
isValid &= set.Cardinality <= maxCardinality;
var isSafe = true;
if (isValid)
{
isSafe = CheckSet(set, allFaults, !isCurrentLevel);
}
if (isSafe && isCurrentLevel)
{
currentSafe.Add(set);
}
// inform heuristics about result and give them the opportunity to add further sets
foreach (var heuristic in Heuristics)
{
heuristic.Update(setsToCheck, set, isSafe);
}
if (StopOnFirstException && _exceptions.Count > 0)
{
goto returnResult;
}
}
// in case heuristics removed a set (they shouldn't)
foreach (var set in sets)
{
var isSafe = CheckSet(set, allFaults, false);
if (isSafe)
{
currentSafe.Add(set);
}
if (StopOnFirstException && _exceptions.Count > 0)
{
goto returnResult;
}
}
}
returnResult:
// Reset the nondeterministic faults so as to not influence subsequent analyses
foreach (var fault in nondeterministicFaults)
{
fault.Activation = Activation.Nondeterministic;
}
// due to heuristics usage, we may have informatiuon on non-minimal critical sets
var minimalCritical = RemoveNonMinimalCriticalSets();
_results.IsComplete = isComplete;
_results.Time = stopwatch.Elapsed;
_results.SetResult(minimalCritical, _checkedSetCount, _checkedSets, _counterExamples, _exceptions);
return(_results);
}
