Re: [Haskell-cafe] Precise timing

to clarify, the -C flag is an RTS flag On Sun, Oct 19, 2014 at 12:48 AM, Carter Schonwald < carter.schonwald@gmail.com> wrote:

if you care about precise timing (at the cost of of some loss of throughput) you can compile your code with -fno-omit-yields, and also the context switching timer see eg http://www.haskell.org/ghc/docs/7.4.2/html/users_guide/using-concurrent.html

default context switching rate for threads is -C0.02 (20ms), but you can set the rate as small as you like, and -C0 will trigger a context switch at every yield.

happy experimenting!

On Sat, Oct 18, 2014 at 10:19 PM, Brandon Allbery wrote:

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On Sat, Oct 18, 2014 at 9:36 PM, Jeffrey Brown wrote:

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threadDelay is guaranteed http://hackage.haskell.org/package/base-4.7.0.1/docs/Control-Concurrent.html...

to wait at least as long, but potentially longer than, what the caller specifies. Another potential problem could be buffering in printf. (Eventually I intend to replace the printf statement with OSC output to a sound generator.)

This isn't going to be solved completely within Haskell; the behavior of threadDelay is the behavior of the system scheduler for a normal process, possibly modified by garbage collection delays. You'll need to switch the process to a realtime scheduling class to remove --- or at least reduce --- the OS's contribution to the uncertainties in sleep times.

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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