[Haskell-cafe] style question: Writer monad or unsafeIOToST?

[Gregory Wright]

Hi Bulat,

On Aug 25, 2006, at 3:36 AM, Bulat Ziganshin wrote:

> Hello Gregory,
>
> Friday, August 25, 2006, 3:08:09 AM, you wrote:
>
>> Some performance data:  using unsafeIOToST to write log messages
>> directly to the output, the simulation does 10^7 state updates in
>> about 45 seconds
>> on my 1.5 GHz ppc G4.  Using LogT, with a list of strings as the  
>> monoid,
>> it takes about 7 minutes to do the same, and the system swaps heavily
>> during the last few minutes.  Not surprising, given that the mappend
>> operation is not very efficient for the list monoid.
>
> are you sure that you know how monads are implemented? IO/ST monads
> just organize order of execution, without any penalty comparing
> to imperative languages. but other monads and all monad transformers
> add their data to the tuple passed between monad operations. and this
> makes their execution significantly slower. you can read more about  
> this
> in http://sigfpe.blogspot.com/2006/08/you-could-have-invented- 
> monads-and.html
>

No doubt my understanding of the underlying implementation could
be improved.  I will read the reference. Thank you.


> about multi-threading - you can (and should!) use ghc's internal
> concurrency with forkIO. it is a perfect way - with minimal overhead
> and ability to use any Haskell features in each thread without
> fighting against multi-threading implementation
>

I will give this a try when I get to that stage in the project.

Best Wishes,
Greg

> -- 
> Best regards,
>  Bulat                            mailto:Bulat.Ziganshin at gmail.com
>
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