GeNIe and SMILE

[svenr]

Hello Forum!

I am using the Smile.net wrapper to access SMILE from an ASP.net web application.
In order to avoid the expensive loading of a Network from disk using the ReadFile-method for every request, I am keeping a "master copy" in memory and then use the .Clone()-method to give out "fresh" networks to handle the requests.
Occasionally, I am getting AccessViolationExceptions from within the .Clone()-call and, more seldomly, during the Finalize()-method of the Network-object (apparently, when Garbage Collection runs).

What's wrong here?

[shooltz]

[svenr]

[shooltz]

[svenr]

Thanks for the hints with AddMemoryPressure and Network.Dispose().
I was unable to reproduce the exception with the code that uses Dispose() so it appears that your suggestions did the trick (although the bug was not reliably reproducible even before - will report back if it re-surfaces).

For completeness, I have attached a more comprehensive example to this post. It contains an updated BayesContainer.cs that uses both suggestions.
The attachment also contains an example of how I use SMILE in a WCF webservice. The project should compile in VS2008 once you put a smilenet.dll into its directory.
It should show that accesses to a SMILE.Network instance are single threaded, with the exception of the cloning itself (which is synchronized for this reason). The cloned SMILE.Network is only used as a local member within one method.

[svenr]

Stupid me, why am I posting so bold things...

Here is the relevant part of two stacktraces that may be of help:

[shooltz]

[svenr]

I got the debug build and will deploy it to the server ASAP.
Will report back with any new insights...

[svenr]

Hi! It's me again - with bad (or, let's say, ambivalent) news...

The problem didn't surface again for quite some time now, mostly because of excessive synchronisation which effectively meant that the whole application ran single-threadedly...

In the meantime, thanks to your suggestion, I tried to avoid the expensive per-request cloning by implementing a pool from which threads may acquire SMILE.Networks.
The pool is built by reading one .xdsl file from disk several times (i.e. there should not be any connections between the Network-objects in the pool). Threads return Networks to the pool after they have used them.

Using the pool with a size of 1 (i.e., serialize all threads to use one single SMILE.Network) is fine. Setting the pool size to 2 or more causes an AccessViolationException under the following circumstances: When UpdateBeliefs() was executed on two ore more Networks in parallel, the next execution of UpdateBeliefs() on one of these Networks (done by the next thread to get it from the pool) throws the exception. In fact, calling UpdateBeliefs() twice within the same thread would also throw the exception, if another thread completed a call to UpdateBeliefs() between both calls.

However, the exception is thrown only for some BayesianAlgorithmTypes:
Henrion, HeuristicImportance and LSampling fail, while AisSampling, BackSampling, EpisSampling, Lauritzen and SelfImportance are ok.
The exception even occurs when the pool contains wholly different networks (i.e. read from separate files).
It appears to me that the first algorithms use some variable that is shared across the library and not private to the Network object (something 'static', perhaps?) which leads to interferences.

I have attached a sample project which implements the described behaviour and reproduces the Exception reliably (increase NUMBER_OF_THREADS in case it does not ).
It is for VS2008 but I guess the .cs files can easily be compiled in other versions of Visual Studio. In any case, make sure to have a smilenet.dll referenced by the project to build it.

If you need any further information, let me know.

[shooltz]

[svenr]

[svenr]