Are there any “gotchas” I should know about with regards to using multithreading in JGAP?

Question

I'm working on a Genetic Programming project that tries to generate GPs that would represent an image. My approach is to split the image into different independent sections and having seperate threads do the evolution jobs on them.

Since things are going to be asynchronous, naturally you'd want objects to be independent as well. The problem is that I noticed that certain objects in JGAP are actually shared variables, so they are going to be shared between threads, and that would cause a lot of issues. For example, I noticed that all Variables with the same name are the same, which means that if I wanted to evaluate more than one IGPProgram at the same time I'd have to lock the variable, which could really hamper performance.

I also noticed that if you tried to create more than one GPConfiguration, the program would complain that you would have to reset it first. So this seems to me all GPConfigurations are shared (i.e. you can't have multiple threads create multiple configurations at the same time), which is a problem because creating GPProblems can take a lot of time, and I'm creating a lot of GPProblems, so I was hoping to reduce the time taken by splitting the work into multiple threads.

Are there any "gotchas" that I would need to know about when working with JGAP and threads? Unfortunately, multithreading isn't touched upon too much in the JGAP documentation and I was hoping I'd get some advice from people who might have experience with JGAP.

Answer 1

If you want some variable do not shared across thread, and make minor changes to let the code suppport multithread. you can using ThreadLocal.

When and how should I use a ThreadLocal variable?

Answer 2

According to the FAQ, JGAP "does support multi-threaded computation". However, this doesn't mean that the entire API/object graph is fully thread safe. Do you have a code sample that demonstrates the problem you are having? I don't think you're going to get a canonical answer without refining your question a bit.

There is a threaded example in the JGAP distribution zip under examples/src/examples/simpleBooleanThreaded.