[Haskell-cafe] First call to putStr takes far more time than subsequent calls

Ben Gunton ben.gunton at gmail.com
Thu Jul 9 20:26:59 UTC 2015

The thing is, if I switch the "putStr """ in the replicateM to "evaluate $
force t1", the first iteration still takes way longer. Are there things to
setup even with that? Is there a way to pre-setup all the things that need
to be setup?

This is also on Linux, with GHC 7.10.1, and no optimizations.

On Thu, Jul 9, 2015 at 2:24 PM, Brandon Allbery <allbery.b at gmail.com> wrote:

> On Thu, Jul 9, 2015 at 4:17 PM, Ben Gunton <ben.gunton at gmail.com> wrote:
>> In this example, the first putStr inside the replicateM_ takes far longer
>> than subsequent putStrs. If I add in a putStr at the top (the commented
>> line), each iteration takes the same. (Though I presume I just shifted the
>> long execution to the putStr on top).
> If I had to guess, delayed setup of the Handle associated with stdout.
> This will include setting up buffering (including querying the OS to find
> out whether output is a tty-like device or not, so as to enable or disable
> block buffering; note that this may be especially expensive on Windows,
> where there is IIRC no simple way to determine whether running in e.g. a
> cmd.exe window or not, as the OS has no concept of pseudo-ttys); also,
> setting up output encoding and such. Probably also other details.
> --
> brandon s allbery kf8nh                               sine nomine
> associates
> allbery.b at gmail.com
> ballbery at sinenomine.net
> unix, openafs, kerberos, infrastructure, xmonad
> http://sinenomine.net
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