a faster, accumulating mapM (was Re: [Haskell-cafe] mapM
vs mapM_ performance)
simonpj at microsoft.com
Fri Apr 25 04:42:28 EDT 2008
| 1) Why is the Prelude mapM so slow? It seems like running 10x slower
| than mapM_ when generating only 50,000 return values is a problem.
All this does seem odd. I've submitted a ticket so we don't forget it
It appears to be some bad (possibly even non-linear) run-time system or garbage collector effect, caused by the very deep stack.
Thanks for persisting with this. I'd expect mapM to be a bit slower, but not *that* much.
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