I have a Java program that runs many small simulations. It runs a genetic algorithm, where each fitness function is a simulation using parameters on each chromosome. Each one takes maybe 10 or so seconds if run by itself, and I want to run a pretty big population size (say 100?). I can't start the next round of simulations until the previous one has finished. I have access to a machine with a whack of processors in it and I'm wondering if I need to do anything to make the simulations run in parallel. I've never written anything explicitly for multicore processors before and I understand it's a daunting task. 

So this is what I would like to know: To what extent and how well does the JVM parallel-ize? I have read that it creates low level threads, but how smart is it? How efficient is it? Would my program run faster if I made each simulation a thread? I know this is a huge topic, but could you point me towards some introductory literature concerning parallel processing and Java?

Thanks very much!

**Update:**
Ok, I've implemented an ExecutorService and made my small simulations implement Runnable and have run() methods. Instead of writing this: 

```
Simulator sim = new Simulator(args); 
sim.play(); 
return sim.getResults(); 

```

I write this in my constructor:

```
ExecutorService executor = Executors.newFixedThreadPool(32);

```

And then each time I want to add a new simulation to the pool, I run this:

```
RunnableSimulator rsim = new RunnableSimulator(args); 
exectuor.exectue(rsim); 
return rsim.getResults(); 

```

The `RunnableSimulator::run()` method calls the `Simulator::play()` method, neither have arguments.

I think I am getting thread interference, because now the simulations error out. By error out I mean that variables hold values that they really shouldn't. No code from within the simulation was changed, and before the simulation ran perfectly over many many different arguments. The sim works like this: each turn it's given a game-piece and loops through all the location on the game board. It checks to see if the location given is valid, and if so, commits the piece, and measures that board's goodness. Now, obviously invalid locations are being passed to the commit method, resulting in index out of bounds errors all over the place.

Each simulation is its own object right? Based on the code above? I can pass the exact same set of arguments to the `RunnableSimulator` and `Simulator` classes and the runnable version will throw exceptions. What do you think might cause this and what can I do to prevent it? Can I provide some code samples in a new question to help?