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

Here is the same thing with no console usage, just forcing the time value. The first-iteration-delay seems to happen at the first IO-ish thing being evaluated. http://lpaste.net/136254 On Thu, Jul 9, 2015 at 2:26 PM, Ben Gunton wrote:

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 wrote:

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On Thu, Jul 9, 2015 at 4:17 PM, Ben Gunton wrote:

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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@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net