/// <summary>
/// This method is used in a DFS exploration of nondet choice. It will pop off bool
/// choices that are 1 until it reaches a 0 that will then be changed to a 1. The
/// NextNondetChoiceIndex will be reset ready for replay.
/// </summary>
public bool BacktrackNondetChoices()
{
if (this.NondetChoices is null)
{
return(false);
}
Debug.Assert(this.NextNondetChoiceIndex == this.NondetChoices.Count, "this.NextNondetChoiceIndex != this.NondetChoices.Count");
this.NextNondetChoiceIndex = 0;
while (this.NondetChoices.Count > 0)
{
NonDetChoice choice = this.NondetChoices[this.NondetChoices.Count - 1];
Debug.Assert(choice.IsBoolChoice, "DFS DPOR only supports bool choices.");
if (choice.Choice == 0)
{
choice.Choice = 1;
this.NondetChoices[this.NondetChoices.Count - 1] = choice;
return(true);
}
Debug.Assert(choice.Choice == 1, "Unexpected choice value.");
this.NondetChoices.RemoveAt(this.NondetChoices.Count - 1);
}
return(false);
}
/// <summary>
/// Get a nondet choice. This may replay a nondet choice or make (and record) a new nondet choice.
/// </summary>
public int MakeOrReplayNondetChoice(bool isBoolChoice, IRandomNumberGenerator rand)
{
Debug.Assert(rand != null || isBoolChoice,
"A DFS DPOR exploration of int nondeterminstic choices " +
"is not currently supported because this won't scale.");
if (this.NondetChoices is null)
{
this.NondetChoices = new List <NonDetChoice>();
}
if (this.NextNondetChoiceIndex < this.NondetChoices.Count)
{
// Replay:
NonDetChoice choice = this.NondetChoices[this.NextNondetChoiceIndex];
++this.NextNondetChoiceIndex;
Debug.Assert(choice.IsBoolChoice == isBoolChoice, "choice.IsBoolChoice != isBoolChoice");
return(choice.Choice);
}
// Adding a choice.
Debug.Assert(this.NextNondetChoiceIndex == this.NondetChoices.Count, "this.NextNondetChoiceIndex != this.NondetChoices.Count");
NonDetChoice ndc = new NonDetChoice
{
IsBoolChoice = isBoolChoice,
Choice = rand is null ? 0 : (isBoolChoice ? rand.Next(2) : rand.Next())
};
this.NondetChoices.Add(ndc);
++this.NextNondetChoiceIndex;
return(ndc.Choice);
}
