public TmRunResult (ITmRunBase tm)
{
if (tm == null)
throw new ArgumentNullException ();
Machine = tm;
}
public TmRunResult(ITmRunBase tm)
{
if (tm == null)
{
throw new ArgumentNullException();
}
Machine = tm;
}
public void Detect (ITmRunBase tm)
{
if (tm.Shifts % 1000 == 0) { // TODO this does not work well with block transitions
var proof = IsIndefinite (tm);
if (proof != null) {
tm.Result.SetNonhalting (proof);
}
}
}
public void Detect(ITmRunBase tm)
{
if (tm.Shifts % 1000 == 0) // TODO this does not work well with block transitions
{
var proof = IsIndefinite(tm);
if (proof != null)
{
tm.Result.SetNonhalting(proof);
}
}
}
private string IsIndefinite(ITmRunBase tm)
{
if (tm.Tape is ISimpleTape) // todo what about MM?
{
var tape = tm.Tape as ISimpleTape;
HeadPosition atEnd = tm.Tape.IsAtEnd;
if (atEnd != HeadPosition.Neither && tape.ReadSingle() == 0)
{
var closure = tm.Q.TransitiveClosure(
t => t != null && t.Read == 0,
t => t.Direction != (int)atEnd);
if (closure != null && !closure.Contains(tm.Definition.Qr))
{
DebugStats_Indefinite_TrivialRunner++;
return(""
+ "Runs indefinitely. Reason: "
+ "We're at the end of the tape and the tape is already 0. "
+ "All further transitions reached via input 0 only direct further away. "
+ "But those nodes do not contain the exit. "
+ "Thus we're certainly in an infinite run.");
}
}
}
ulong nTape = tm.Tape.TotalTapeLength + 1;
if (nTape < 30)
{
int usedStates = tm.Definition.Q.Count(q => q.Value.Sources.Any());
ulong requiredSpace = (ulong)usedStates * nTape * (ulong)(2 << (int)nTape);
if (tm.Shifts > requiredSpace)
{
DebugStats_Indefinite_SpaceTooSmall++;
return(""
+ "Runs indefinitely. Reason: "
+ "The tape used is too small to hold as many different configurations as there have been shifts. "
+ "Used states: " + usedStates + ", required space: " + requiredSpace + ", shifts: " + tm.Shifts + " "
+ "(This can only be used for small tapes.)");
}
}
return(null);
}
private string IsIndefinite (ITmRunBase tm)
{
if (tm.Tape is ISimpleTape) { // todo what about MM?
var tape = tm.Tape as ISimpleTape;
HeadPosition atEnd = tm.Tape.IsAtEnd;
if (atEnd != HeadPosition.Neither && tape.ReadSingle () == 0) {
var closure = tm.Q.TransitiveClosure (
t => t != null && t.Read == 0,
t => t.Direction != (int) atEnd);
if (closure != null && !closure.Contains (tm.Definition.Qr)) {
DebugStats_Indefinite_TrivialRunner++;
return ""
+ "Runs indefinitely. Reason: "
+ "We're at the end of the tape and the tape is already 0. "
+ "All further transitions reached via input 0 only direct further away. "
+ "But those nodes do not contain the exit. "
+ "Thus we're certainly in an infinite run.";
}
}
}
ulong nTape = tm.Tape.TotalTapeLength + 1;
if (nTape < 30) {
int usedStates = tm.Definition.Q.Count (q => q.Value.Sources.Any ());
ulong requiredSpace = (ulong) usedStates * nTape * (ulong) (2 << (int) nTape);
if (tm.Shifts > requiredSpace) {
DebugStats_Indefinite_SpaceTooSmall++;
return ""
+ "Runs indefinitely. Reason: "
+ "The tape used is too small to hold as many different configurations as there have been shifts. "
+ "Used states: " + usedStates + ", required space: " + requiredSpace + ", shifts: " + tm.Shifts + " "
+ "(This can only be used for small tapes.)";
}
}
return null;
}