[Haskell-cafe] GHC 6.7 on Windows / containers-0.1 package?
bf3 at telenet.be
Fri Sep 21 15:38:36 EDT 2007
Thanks for the info, very interesting. Yes, I'm using GHCi, and I'm
using forkOS, and I'm using OpenGL...
Since I'm used to write heavily multi-threaded/multi-core code in
imperative languages, I would like to understand more about the existing
execution models, and those "black holes"... Understanding the low-level
details helps a lot for me.
Actually the problem was caused by (yet another) strict pattern match in
my code, which should have been lazy. I find it strange that this would
cause 0% CPU time... But then again I don't understand the details of
how GHCi/GHC works. I did read the book "Modern Compiler Design"
(http://www.cs.vu.nl/~dick/MCD.html) which implements a basic Haskell
interpreter & compiler, so I got an introduction.
Anyway, it's a very good learning experience for me to "redo" FRP from
scratch, as I encounter all pitfalls (such as the need for memoization
when using recursive streams, the need for lazy pattern matching, the
space leaks sneaking up on you, etc). Once I get to understand these in
detail, I'll try to re-read the existing papers on FRP, which I hardly
understood initially :-)
Stefan O'Rear wrote:
> On Wed, Sep 19, 2007 at 10:24:24PM +0100, Neil Mitchell wrote:
>> Hi Peter,
>>> So I grabbed ghc-6.7.20070824 (=the latest one for Windows I could find)
>>> and the "extra-libs", compiled and installed the GLUT package (which I
>>> needed), but when I compile my library, I get
>>> Could not find module `Data.Map':
>>> it is a member of package containers-0.1, which is hidden
>> All dependencies etc. have changed when going to 6.7/6.8 - you are
>> probably better off using 6.6.1 for now.
>> I also don't think that the debugger will help you track down infinite
>> loop style errors. You might be better off posting the code and asking
>> for help.
> You said 0% CPU. That's *very* important. It means that you are using
> the threaded runtime (GHCi?), and that you triggered a blackhole. You
> should be able to handle this by compiling your program with -prof (do
> *not* use -threaded!), and running with +RTS -xc. With luck, that will
> give you a backtrace to the infinite loop.
> PS. blackholes are a serious dark corner of GHC's execution model,
> chances are better than even that if you try to use the debugger for
> this you will discover a new and (for you) crippling bug. I wouldn't
> recommend it.
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