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

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 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 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

...

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

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