NullReferenceException occurs during parallel execution of experiment optmizers

[mkommend]

If two optimizers of an experiment are executed side by side a NullReferenceExecution could occur. The reason behind this is that the ExecutionContext of a parameter or operator in an executing algorithm is set to null during the clean up of another algorithm.

From this it can be inferred that while iterating an object graph, objects belonging to a different algorithm are discovered.

[mkommend]

r6572: Corrected a cloning bug in OperatorGraphVisualizationInfo.

[abeham]

I still experience this bug from time to time, although it's difficult to reproduce. I'll see what I can do.

[abeham]

I've had an error again when executing optimizers in parallel in an experiment, though the exception is an InvalidOperationException. It reads: "Collection was modified...". A screenshot is attached, unfortunately the application crashed and I couldn't access the exception dialog again. It seems to stem from a race condition somewhere in the RunCollection or RunCollectionView.

[ascheibe]

I have just got an exception in the experiment view. I have created an experiment with different mutation operators and mutation rates for GA/VRP. I ran 2 of the experiments and got the following exception:

ObjectDisposedException: The CancellationTokenSource associated with this CancellationToken has been disposed.
at System.Threading.CancellationToken.ThrowIfSourceDisposed()
at System.Threading.Tasks.Task.TaskConstructorCore(Object action, Object state, CancellationToken cancellationToken, TaskCreationOptions creationOptions, InternalTaskOptions internalOptions, TaskScheduler scheduler)
at System.Threading.Tasks.TaskFactory.StartNew(Action`1 action, Object state, CancellationToken cancellationToken)
at HeuristicLab.ParallelEngine.ParallelEngine.Run(Object state) in C:\dev\trunk\sources\HeuristicLab.ParallelEngine\3.3\ParallelEngine.cs:line 72
at HeuristicLab.ParallelEngine.ParallelEngine.Run(CancellationToken cancellationToken) in C:\dev\trunk\sources\HeuristicLab.ParallelEngine\3.3\ParallelEngine.cs:line 51
at HeuristicLab.Core.Engine.Run(Object state) in C:\dev\trunk\sources\HeuristicLab.Core\3.3\Engine.cs:line 153
at System.Threading.Tasks.Task.Execute()
   

OperatorExecutionException: An exception was thrown by the operator "SubScopesProcessor": The number of operators doesn't match the number of sub-scopes at depth 1
at HeuristicLab.ParallelEngine.ParallelEngine.Run(Object state) in C:\dev\trunk\sources\HeuristicLab.ParallelEngine\3.3\ParallelEngine.cs:line 115
at HeuristicLab.ParallelEngine.ParallelEngine.Run(CancellationToken cancellationToken) in C:\dev\trunk\sources\HeuristicLab.ParallelEngine\3.3\ParallelEngine.cs:line 51
at HeuristicLab.Core.Engine.Run(Object state) in C:\dev\trunk\sources\HeuristicLab.Core\3.3\Engine.cs:line 153
at System.Threading.Tasks.Task.Execute()
-----
ArgumentException: The number of operators doesn't match the number of sub-scopes at depth 1
at HeuristicLab.Operators.SubScopesProcessor.Apply() in C:\dev\trunk\sources\HeuristicLab.Operators\3.3\SubScopesProcessor.cs:line 74
at HeuristicLab.Operators.Operator.Execute(IExecutionContext context, CancellationToken cancellationToken) in C:\dev\trunk\sources\HeuristicLab.Operators\3.3\Operator.cs:line 120
at HeuristicLab.ParallelEngine.ParallelEngine.Run(Object state) in C:\dev\trunk\sources\HeuristicLab.ParallelEngine\3.3\ParallelEngine.cs:line 99

I'm not really sure what or why it happened and I wasn't able to reproduce it. I thought i post it here, maybe somebody else got this exception or knows what this means, else ignore it as it only happened once and i tried hard to reproduce it.

[mkommend]

I'm not really sure what or why it happened and I wasn't able to reproduce it. I thought i post it here, maybe somebody else got this exception or knows what this means, else ignore it as it only happened once and i tried hard to reproduce it.

This problem is normally related to an cloning error within the algorithm or the problem. As we can be quite sure that there should not be a cloning bug in the GA, my first guess is that there is cloning bug in the VRP problem.

[ascheibe]

I have tested the experiment view again and everything worked fine, so I'm setting this ticket readytorelease.