[Haskell-cafe] Re: help with threadDelay
Ian Lynagh wrote: [moving to glasgow-haskell-bugs] On Wed, Nov 15, 2006 at 11:40:12PM +, Neil Davies wrote: however when -threaded is used you get some interesting effects, including returning too early: Tgt/Actual = 0.000125/0.34s, diff = -0.91s Thanks for the report; I can reproduce it on Linux/amd64. OK, so the bug here is that threadDelay n might return after less than n microseconds. This looks like it's caused by truncation problems when converting times to ticks (where a tick is 1/50 of a second), e.g. while trying to sleep for 1.953125s one run started at 1164157960.773726s which is (Int) 1164157960 * 50 + 773726 * 50 / 100 = (Int) 58207898038.6863 = 58207898038 ticks and woke the thread up at 1164157962.708609s which is (Int) 1164157962 * 50 + 708609 * 50 / 100 = (Int) 58207898135.4305 = 58207898135 ticks The difference is 58207898135 - 58207898038 = 97 ticks. Meanwhile we're trying to sleep for (Int) 50 * 1.953125 = (Int) 97.65625 = 97 ticks However, 1164157962.708609s - 1164157960.773726s = 1.93488311767578s which is 0.0182418823242201s too short. The problem is that we have counted 0.6863 ticks before the start time, not counted 0.4305 ticks before the finish time and have been waiting 0.65625 ticks too short a time. Thus we have counted (0.6863-0.4305 + 0.65625) / 50 == 0.018241 too much time. I think the answer is that let target = now + usecs `quot` tick_usecs in GHC/Conc.lhs should be let target = 1 + now + (usecs + tick_usecs - 1) `quot` tick_usecs I'm also a bit dubious about the use of the constant 50 for the number of ticks per second, but the results with +RTS -V0.001 don't look any more wrong so perhaps I just need to get some sleep. The hardcoded 50 in GHC/Conc.lhs matches up with TICK_FREQ in libraries/base/includes/HsBase.h. It could probably be made larger without any ill effects. I agree that we should round up the target time to the nearest tick rather than rounding down, though. Cheers, Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why are new releases of libraries required for every GHC release?
On Wed, 2006-11-22 at 09:12 +, DavidA wrote: Some recent comments suggested that every time there is a new GHC release, there needs to be a new wxHaskell release (or insert name of other library here) to work with it. This seems to be true even for minor upgrades, like 6.4.1 - 6.4.2. These GUI libs tend only to break on major releases like 6.2 - 6.4 and 6.4 - 6.6. In both cases this was due to changes in the way packages are managed. Since these GUI libs are both pretty large and made of several packages they were affected. Many simpler projects were fine with the transition. Why is this? Does GHC break binary compatibility at every release? Is this avoidable? Yes this is what you're thinking about with minor upgrades like 6.4.1 - 6.4.2, so any binary packages, eg windows installers need to be rebuilt from source to work with the new ghc version. This makes using Haskell unnecessarily hard compared to other platforms. Well, usually it's only a rebuild so as long as your build system is ok, it's not too hard. Duncan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Type Error. Why!?
On Wed, 22 Nov 2006, Neil Mitchell wrote: http://www.haskell.org/hawiki/MonomorphismRestriction Is there really not a page on the new wiki that explains that MR? We should also have a nice big FAQ, as this is often asked about. http://www.haskell.org/haskellwiki/Category:FAQ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Articles on programming with (IO) exceptions in Haskell?
Hello Magnus, Tuesday, November 21, 2006, 9:07:40 PM, you wrote: I'm having problems finding a good introduction to exceptions. Yet Another Haskell Tutorial leaves it for chapter 10, which is empty. I'd prefer something that suits a noob. :-) Tackling the awkward squad: monadic input/output, concurrency, exceptions, and foreign-language calls in Haskell http://research.microsoft.com/Users/simonpj/papers/marktoberdorf/marktoberdorf.ps.gz -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: help with threadDelay
Ian/Simon(s) Thanks - looking forward to the fix. It will help with the real time enviroment that I've got. Follow on query: Is there a way of seeing the value of this interval from within the Haskell program? Helps in the calibration loop. Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] trivial ghc problem, help needed
clawsie:
i have a program tb.hs:
---
module Main where
import Network.URI (URI(..), URIAuth(..), parseURI)
myFunc :: String - Maybe URI
myFunc u = parseURI u
main = do { return () }
---
when i attempt to build it with ghc, i get the following output:
tb.o: In function `Main_myFunc_info':
(.text+0x11): undefined reference to
`networkzm2zi0_NetworkziURI_parseURI_closure'
tb.o: In function `Main_myFunc_srt':
(.rodata+0x0): undefined reference to
`networkzm2zi0_NetworkziURI_parseURI_closure'
collect2: ld returned 1 exit status
any clue why? i would send this to the ghc list but i presume my issue
is due to a trivial misunderstanding of the language
Assuming you have the Network package installed, you need to tell the
compile to link in the extra network library. The above is a linker
error.
Adding
--make
or
-package network
to the command line should do the trick.
-- Don
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[Haskell-cafe] YCR2JS Programmers Guide Draft available
Hi, I have finished typing in the draft of low-level programming guide for Yhc Core to Javascript converter. Everyone interested in future use of this tool is encouraged to read and review the Guide. Its purpose is to give some ideas about interaction of Haskell programs converted into Javascript with a web browser on the lowest possible level, without application frameworks and support libraries (just because these haven't been developed). Any feedback and ideas are appreciated. The document is located at: http://haskell.org/haskellwiki/Yhc/Javascript/Programmers_guide Thanks. -- Dimitry Golubovsky Anywhere on the Web ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
