[Haskell-cafe] forkIO on GHCI does not seem to spawn the thread in the background on some OSs

[David Leimbach]

On Tuesday, February 8, 2011, C K Kashyap <ckkashyap at gmail.com> wrote:
>
> I can't reproduce this. What are you using as the action?
>
> I've tried bottoms, and tight loops whose Core contains no allocations, and not
> managed to lock up the prompt, or seen ghci using more threads than I have
> cores.
>
> One thing that may give the appearance of locking up the prompt is if
> the thread starts reading from the terminal and your commands no longer make it
> to the interpreter.
>
>> It is  not always a thread.  ForkIO creates a spark and then the
>> scheduler  decides when sparks should be scheduled to threads.  Thus
>> you get a  guarantee of concurrent but not parallel execution.
>
> That is not correct - it is "par" that creates sparks may be discarded.
>
> forkIO always creates new threads, though it is of course up to the scheduler
> when the threads are executed, and how many cores are used.
>
>> Are you running with  threads enabled?
>
> That is, was your ghci compiled with -threaded? This mostly
> depends on the version. what version of ghc are you running, and how did you
> install it?
>
>
>
>
> Sorry ... extremely sorry ... my bad ... for some reason, I was omitting the call to forkIO :( when I was trying on other platforms.
> Regards,Kashyap
>
:-)