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Today's Topics:
1. Re: optimisation of code (PICCA Frederic-Emmanuel)
2. Re: optimisation of code (PICCA Frederic-Emmanuel)
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Message: 1
Date: Mon, 1 Oct 2018 16:59:39 +0000
From: PICCA Frederic-Emmanuel
<frederic-emmanuel.pi...@synchrotron-soleil.fr>
To: "The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell" <beginners@haskell.org>
Subject: Re: [Haskell-beginners] optimisation of code
Message-ID:
<a2a20ec3b8560d408356cac2fc148e53015b330...@sun-dag3.synchrotron-soleil.fr>
Content-Type: text/plain; charset="us-ascii"
> Hi,
> Current code re-checks file existence always in same order, so worst case is
> - N files and only last of them does not exists.
> In that case this code will re-check (N-1) files during each consecutive
> retry.
> This can be optimized by moving already existing files to the end of file
> list(or dropping them from list completely, if files are only > > added but
> never removed).
> For this you could re-write `allFilesThere` something like:
> allFilesThere fs = liftIO $ do
> existing, non_existing <- partitionM (doesFileExist . fromAbsFile) fs
< return (non_existing++ existing, null non_existing)
> Then allFilesThere could start next iteration by checking previously
> non-existing files and probably failing much faster.
thanks a lot, files are never removed, so I can forget already checked files :)
------------------------------
Message: 2
Date: Mon, 1 Oct 2018 17:01:48 +0000
From: PICCA Frederic-Emmanuel
<frederic-emmanuel.pi...@synchrotron-soleil.fr>
To: "The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell" <beginners@haskell.org>
Subject: Re: [Haskell-beginners] optimisation of code
Message-ID:
<a2a20ec3b8560d408356cac2fc148e53015b330...@sun-dag3.synchrotron-soleil.fr>
Content-Type: text/plain; charset="us-ascii"
> My first instinct is to just use anyM instead of allM
> allFilesThere :: MonadIO m => [Path Abs File] -> m Bool
> allFilesThere fs = liftIO $ anyM (not . doesFileExist . fromAbsFile) fs
> However you'll now have the opposite problem. It will take a lot of
> resources when all the files are there. But maybe that is okay for your use
> case?
I need to reduce the worload when a file is missing.
I like a lot the partition idea.
Cheers
Frederic
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