What is the GPars default pool size?

Question

I thought this would have been an easy thing to find but I've failed.

If I use GPars in my Groovy application and I don't specify a pool size how many threads will be created? Is there a default pool size without setting one?

// How many threads will be created? What is the default pool size?
GParsExecutorsPool.withPool {
    // do stuff...
}

Expensive

Answer 1

It is (by default) set to

private static int defaultPoolSize() {
  return Runtime.getRuntime().availableProcessors() + 1;
}

You can alter this (I believe) by setting a System property called gpars.poolsize to a valid Integer

Sosthenna

Why is it "availableProcessors" plus one? I'd expect it to be minus one, to leave one available for other systems? (unless of course you only have one to begin with!) – Kent

Answer 2

As many as you have CPU units plus one, as shown by the PoolUtils class source, or from a system property

retrieveDefaultPoolSize() is called once as a final static variable by the GParsPool class when it's initialized

Roseola

Thanks, upvoted you for the source link. But had to give tim_yates the answer for being first :-) – Expensive