I don't know if this would be worth, but theoretically one could go on and evaluate those thunks that: a) would be evaluated anyway (after the current IO operation have been completed) b) do not depend on the result of the current operation And, of course, the GC could work in this time also. Nicu
-----Ursprüngliche Nachricht----- Von: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Im Auftrag von Brent Yorgey Gesendet: Dienstag, 29. April 2008 16:42 An: Daniil Elovkov Cc: haskell-cafe@haskell.org Betreff: Re: [Haskell-cafe] Something like optimistic evaluation On Mon, Apr 28, 2008 at 6:09 PM, Daniil Elovkov <[EMAIL PROTECTED]> wrote: Hello Somewhat on the topic of optimistic evaluation, I've just thought of another way to evaluate thunks. When the program is about to block on some IO, what if we start a thread to evaluate (any) unevaluated thunks. We'll have additional system thread, but the blocked one will not actually consume any processor time. This would take place only when the program is compiled as threaded and run with -N k, k>1. The RTS knows at least about some operations that will block, those which IO operations are implemented with. for example. It could merely start a process of evaluating any (or something more clever) outstanding thunks right before going into one of those operations and stop it when it's back. Of course, it's not like optimistic evaluation because we don't avoid creating thunks. But in a sense it's similar. It could also be compared with incremental garbage collection :) Has something like that been done, discussed? This sounds like it could be helpful in certain circumstances, but in many cases it could probably lead to unpredictable (and uncontrollable!) memory usage. I could imagine a situation where my program is running along just fine, and then one day it takes a long time to do a read from the network due to latency or whatever, and suddenly memory usage shoots through the roof, due to evaluation of some infinite (or even just very large) data structure. -Brent
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