[Haskell-cafe] Memory Management and Lists

[Tom Ellis]

Yes, this is a very neat trick and very effective.  (I couldn't acutally
find it on Hoogle.  Does anyone have a link?)

On Thu, Jul 14, 2016 at 07:45:33AM +0000, Robin Palotai wrote:
> For deepseq also see the"Once trick". I'm surprised it's not quoted more
> often. In fact our would make sense to mention it in the deepseq docs.
> 
> On Wed, Jul 13, 2016, 21:32 David Feuer <david.feuer at gmail.com> wrote:
> 
> > You have to be careful with deepseq. Using it in the wrong place can
> > lead to very bad performance. It's a big hammer. Its blow can
> > sometimes be softened using the NF type from the nf package, but it's
> > really not the right thing most of the time.
> >
> > On Tue, Jul 12, 2016 at 11:56 PM, William Yager <will.yager at gmail.com>
> > wrote:
> > > You probably want Control.DeepSeq. No extraneous work doing addition that
> > > way either.
> > >
> > > Will
> > >
> > > On Tue, Jul 12, 2016 at 11:28 PM, Christopher Howard <ch.howard at zoho.com
> > >
> > > wrote:
> > >>
> > >> After pondering this problem some more, I found a solution to the
> > >> problem was to introduce strictness, not deep down in the StateReader
> > >> monad, but rather at the top level, i.e., forcing evaluation of each
> > >> Matrix as soon as it is pulled of the list of Matrices. I found I could
> > >> do this simply by summing all the elements in each matrix and printing
> > >> the sum to std out. With this approach, i successfully run the full
> > >> program and never even saw my memory performance graph move up.
> > >>
> > >> I suppose there might be a way to do the same thing more efficiently
> > >> with seq...?
> > >>
> > >> On 07/12/2016 06:39 PM, Christopher Howard wrote:
> > >> > I guess I was hesitating on posting the entire program source code in
> > an
> > >> > cafe email. I suppose I could send you a tarball, if you really wanted
> > >> > it...
> > >> >
> > >> > Matrix is from Data.Matrix
> > >> >
> > >> > <
> > http://hackage.haskell.org/package/matrix-0.3.5.0/docs/Data-Matrix.html>.
> > >> >
> > >> > It is hard to understand how thunks alone would explain it... there
> > >> > would be at most 2000 thunks, right? Unless... Could there be a thunk
> > >> > for every single call to getElem? That would be a lot of thunks!
> > >> >
> > >> > Somebody suggested adding some strictness here... could you elaborate
> > on
> > >> > that? I tried inserting seq, but I didn't really understand how I was
> > >> > supposed to use it...
> > >> >
> > >>
> > >> --
> > >> http://qlfiles.net
> > >> To protect my privacy, please use PGP encryption. It's free and easy
> > >> to use! My public key ID is 0x340EA95A (pgp.mit.edu).
> > >>
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