Things I Learned from ACCU 2010

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Walter Bright Wrote:

> bearophile wrote:
> > Walter Bright:
> >> OCaml has a global interpreter lock which explains its behavior. Russell
> >> didn't know why the Haskell behavior was so bad. He allowed that it was
> >> possible he was misusing it.
> > 
> > You have just the illusion to have learned something about this. Trying to
> > read too much from this single example is very wrong. A single benchmark,
> > written by a person not expert in the language, means nearly nothing. You
> > need at least a suite of good benchmarks, written by people that know the
> > respective languages. And even then, you have just an idea of the situation.
> 
> 
> Fair enough, but in order to dismiss the results I'd need to know *why* the 
> Haskell version failed so badly, and why such a straightforward attempt at 
> parallelism is the wrong solution for Haskell.
> 
> You shouldn't have to be an expert in a language that is supposedly good at 
> parallelism in order to get good results from it.
> 
> (Russel may or not be an expert, but he is certainly not a novice at FP or 
> parallelism.)
> 
> Basically, I'd welcome an explanatory riposte to Russel's results.

This a failure to read the manual, and arguably bad defaults by GHC here.

At the haskell parMap versions work fine when you compile with -threaded, and
run with:  +RTS -N

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