[Haskell-beginners] Real World Haskell: Deprecated Libraries

[Bob Ippolito]

Try using foldl', usually that's the right thing to do for this kind of
data structure.

On Sun, Nov 27, 2016 at 2:39 PM, John Ky <newhoggy at gmail.com> wrote:

> It looks like Haskell stack's profile options are defeating stream fusion.
>
> Anyone know a work-around?
>
>
> On Mon, 28 Nov 2016 at 08:23 John Ky <newhoggy at gmail.com> wrote:
>
>> Hello Haskellers,
>>
>> I have been working through the Real World Haskell chapter on Profiling
>> and Optimisation
>> <http://book.realworldhaskell.org/read/profiling-and-optimization.html>,
>> and got to the section *Advanced techniques: fusion*, where I
>> encountered some code using Data.Array.Vector from the deprecated
>> library uvector.
>>
>> Does anyone know how to rewrite this to not use deprecated libraries?
>>
>> I have tried to use Data.Vector.Unboxed from vector, but my version
>> consumes a lot of memory.
>>
>> The code I have is here:
>>
>> https://github.com/haskell-works/hw-tutorial-performance/
>> blob/master/hw-tutorial-performance-rwhe/Main.hs
>>
>> With that code, I get “1831 MB total memory in use”, which is terrible
>>
>> Build run steps I used were:
>>
>> stack build --executable-profiling --library-profiling --ghc-options="-fprof-auto -rtsopts -auto-all -caf-all -fforce-recomp"
>>
>> time /Users/jky/wrk/haskell-works/hw-tutorial-performance/.stack-work/install/x86_64-osx/lts-7.10/8.0.1/bin/hw-tutorial-performance-rwhe +RTS -sstderr -p -hy -RTS 1e7
>>
>> I get very large numbers of allocations of Pair and Double.
>>
>> There is also a very large upfront allocation ARR_WORDS, which I feared
>> would happen when using Data.Vector
>>
>> Any help appreciated.
>>
>> Cheers,
>>
>> -John
>> ​
>>
>
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