Josef Svenningsson wrote:

One benchmark turned out to give pretty remarkable results. It's the producer/consumer benchmark. I suggest you all take a look at it. The haskell version is six (SIX!!!) times faster than the c version. Hey, what's going on here? I would really like to hear some comments from our dear implementors.

And Simon Peyton-Jones replied:

I guess GHC is fast because it's implementing lightweight threads inside a single OS thread.

Absolutely. Good high-level thread support trumps anything provided by the operating system. I'd second Simon's guess that this was on Linux or some other system where pthreads map one-to-one to OS threads. Similar dramatic performance disparities have cropped up in the Java community. There are Java benchmarks which create thousands of threads; most implementations slow to a crawl when this happens, as the operating system collapses under the crushing load. Those which don't (IBM's Jalapeno, a research JVM, comes to mind) use this as a *big* bragging point. Unless you're mucking with thread priorities, mapping language-level threads one-to-one to operating-system threads is a terrible idea. -Jan-Willem Maessen Eager Haskell project jmaessen@mit.edu