[Haskell-cafe] Concurrency strategy for 2 threads and rare events

JP Moresmau jpmoresmau at gmail.com
Wed Feb 15 19:10:34 CET 2012


Thank you all, I've used a simple IORef and that did the trick.

JP

2012/2/8 Edward Amsden <eca7215 at cs.rit.edu>:
> If you only need one structure for communication (e.g. neither thread
> needs to lock multiple things) you might consider using an IORef, and
> writing/polling it with atomicModifyIORef. It's cheaper than an MVar
> for the case where you don't need to lock multiple threads.
>
> On Wed, Feb 8, 2012 at 2:45 PM, JP Moresmau <jpmoresmau at gmail.com> wrote:
>> No, I meant they seem to be mainly for the use case where the reading
>> thread blocks for more input, and maybe there's a simpler/more
>> efficient way to quickly check if an event has occurred, that's all.
>> If there isn't then a MVar it will be.
>>
>> JP
>>
>> On Wed, Feb 8, 2012 at 7:35 PM, Yves Parès <yves.pares at gmail.com> wrote:
>>> Why do you think it's a lot? MVar are a teeny tiny and convenient primitive
>>> of communication, and I don't see why they wouldn't suit your need.
>>> Sure a throwTo would do the trick... But they're is "do the trick" and "do
>>> the job", you see?
>>>
>>> Using STM and TVars *would* be kind of overkill.
>>>
>>>
>>> 2012/2/8 JP Moresmau <jpmoresmau at gmail.com>
>>>>
>>>> Hello, I'm wondering what's the best strategy to use in the following
>>>> scenario:
>>>> - 2 threads
>>>>  - One perform some work that will take time, possibly go on forever
>>>>  - Another waits for user input (like commands from the keyboard)
>>>> that affects thread 1 (causing it to stop, in the simplest case)
>>>>
>>>> I've read a bit on MVar and channels, but they seem to be a lot for
>>>> cases where the reading thread block for input. In my case, I expect
>>>> to have "something" that thread 2 updates when an event occur, and
>>>> thread 1 checks it regularly. So thread 1 should not block, but should
>>>> check "is there something" and there is, act on it, otherwise continue
>>>> doing what it was currently doing. I suppose I could just tryTakeMVar
>>>> on a MVar, but is there something more adapted to my needs?
>>>>
>>>> Thanks!
>>>>
>>>> --
>>>> JP Moresmau
>>>> http://jpmoresmau.blogspot.com/
>>>>
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>>>> Haskell-Cafe at haskell.org
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>>>
>>>
>>
>>
>>
>> --
>> JP Moresmau
>> http://jpmoresmau.blogspot.com/
>>
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>
>
>
> --
> Edward Amsden
> Student
> Computer Science
> Rochester Institute of Technology
> www.edwardamsden.com



-- 
JP Moresmau
http://jpmoresmau.blogspot.com/



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