[Haskell-cafe] Need help - my haskell code is over 50 times slower than equivalent perl implementation

C K Kashyap ckkashyap at gmail.com
Tue Jun 24 17:07:35 UTC 2014

Thanks Nicholas :) ... and if I understand right doing `seq` would be
equivalent to Strict IO that Darren mentioned. right?


On Tue, Jun 24, 2014 at 10:35 PM, Nicolas Trangez <nicolas at incubaid.com>

> On Tue, 2014-06-24 at 22:02 +0530, C K Kashyap wrote:
> > If I use mapM as suggested by others, I quickly run into -
> >
> > openFile: resource exhausted (Too many open files)
> You should `seq` the calculated length before returning the value,
> otherwise the file descriptor needs to be kept open until the processing
> result is used (when printing the result list), and you exhaust your
> resources.
> Anyway, for giggles I added concurrency support using `async` and IO
> handling using `pipes`/`pipes-bytestring` to my fork in
> https://github.com/NicolasT/haskell-perf-repro/commit/86639daa3b577487e75d385ea825aa58e3c8713b
> Using the sample dataset created by your Makefile, this version is
> somewhat slower than the previous (and your Perl script), but in case
> the dataset is huge (and depending on the block-device you're using, the
> layout of the files on it,... the lot) it might help (or might not).
> Nicolas
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