optimistic evaluation

[Tomasz Zielonka]

On Tue, Feb 07, 2006 at 08:28:51PM +0000, Frederik Eaton wrote:
> What is the status of Rob Ennals' optimistic evaluation work? I'm told
> that it has been removed from GHC. This is extremely depressing to me. 
> Without such a feature available, it becomes very difficult to write
> programs that process large amounts of data in Haskell. In many such
> applications, strictness annotations become not just important for
> performance, but necessary to get a program to function at all. 
> 
> With optimistic evaluation, GHC and Haskell would have been at least
> potential candidates for my programming work in machine learning;
> without it I fear that this is no longer the case.
> 
> Will optimistic evaluation ever be present in GHC again? What is its
> priority, compared to other features which are being implemented? What
> was the last (if any) version of GHC with optimistic evaluation
> present?

I am not sure this is similar to optimistic evaluation, but I was
wondering if it would be possible to find space-leaks at runtime
and try to reduce them.

There's also a related idea to decrease the priority of garbage
producing threads (and/or increase for garbage reducing threads). This
way it would be possible to make the idiomatic Haskell 'wc' (word count)
implementation space efficient with some simple 'par' annotations:

    main = do
        cs <- getContents
        let nChars = length cs
            nWords = length (words cs)
            nLines = length (lines cs)
        (nChars `par` nWords `par` nLines) `seq` return ()
        print (nChars, nWords, nLines)

(I am not sure I used "par" correctly, but I hope you know what I mean).

Best regards
Tomasz

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