[Haskell-cafe] Haskell-Cafe Digest, Vol 113, Issue 11

[Yuriy Solodkyy]

OK. It tells me the same error message in popup, but all the projections
are running after that.

I'll make sure that it does not say any strange errors on empty DB in new
version.

Does it start projections for you as well (even if it says error)?


On Tue, Jan 8, 2013 at 1:00 PM, <haskell-cafe-request at haskell.org> wrote:

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> Today's Topics:
>
>    1. Example programs with ample use of deepseq? (Joachim Breitner)
>    2. Re: Example programs with ample use of deepseq? (Edward Z. Yang)
>    3. Re: Example programs with ample use of deepseq? (Joachim Breitner)
>    4. Re: Example programs with ample use of deepseq? (Johan Tibell)
>    5. Re: Announce: Leksah 0.13.1 (a bit experimental) (Peter Simons)
>    6. Re: Announce: Leksah 0.13.1 (a bit experimental)
>       (Hamish Mackenzie)
>
>
> ---------- Forwarded message ----------
> From: Joachim Breitner <mail at joachim-breitner.de>
> To: Haskell Cafe <haskell-cafe at haskell.org>
> Cc:
> Date: Mon, 07 Jan 2013 13:06:35 +0100
> Subject: [Haskell-cafe] Example programs with ample use of deepseq?
> Dear Haskellers,
>
> I’m wondering if the use of deepseq to avoid unwanted lazyness might be
> a too large hammer in some use cases. Therefore, I’m looking for real
> world programs with ample use of deepseq, and ideally easy ways to test
> performance (so preferably no GUI applications).
>
> I’ll try to find out, by runtime observerations, which of the calls ot
> deepseq could be replaced by id, seq, or „shallow seqs“ that, for
> example, calls seq on the elements of a tuple.
>
> Thanks,
> Joachim
>
> --
> Joachim "nomeata" Breitner
>   mail at joachim-breitner.de  |  nomeata at debian.org  |  GPG: 0x4743206C
>   xmpp: nomeata at joachim-breitner.de | http://www.joachim-breitner.de/
>
>
>
> ---------- Forwarded message ----------
> From: "Edward Z. Yang" <ezyang at MIT.EDU>
> To: Joachim Breitner <mail at joachim-breitner.de>
> Cc: Haskell Cafe <haskell-cafe at haskell.org>
> Date: Mon, 07 Jan 2013 04:20:43 -0800
> Subject: Re: [Haskell-cafe] Example programs with ample use of deepseq?
> There are two senses in which deepseq can be overkill:
>
> 1. The structure was already strict, and deepseq just forces another
> no-op traversal of the entire structure.  This hypothetically affects
> seq too, although seq is quite cheap so it's not a problem.
>
> 2. deepseq evaluates too much, when it was actually sufficient only to
> force parts of the structure, e.g. the spine of a list.  This is less
> common for the common use-cases of deepseq; e.g. if I want to force pending
> exceptions I am usually interested in all exceptions in a (finite) data
> structure; a space leak may be due to an errant closure---if I don't
> know which it is, deepseq will force all of them, ditto with work in
> parallel programs.  Certainly there will be cases where you will want snip
> evaluation at some point, but that is somewhat difficult to encode
> as a typeclass, since the criterion varies from structure to structure.
> (Though, perhaps, this structure would be useful:
>
> data Indirection a = Indirection a
> class DeepSeq Indirection
>     rnf _ = ()
> )
>
> Cheers,
> Edward
>
> Excerpts from Joachim Breitner's message of Mon Jan 07 04:06:35 -0800 2013:
> > Dear Haskellers,
> >
> > I’m wondering if the use of deepseq to avoid unwanted lazyness might be
> > a too large hammer in some use cases. Therefore, I’m looking for real
> > world programs with ample use of deepseq, and ideally easy ways to test
> > performance (so preferably no GUI applications).
> >
> > I’ll try to find out, by runtime observerations, which of the calls ot
> > deepseq could be replaced by id, seq, or „shallow seqs“ that, for
> > example, calls seq on the elements of a tuple.
> >
> > Thanks,
> > Joachim
> >
>
>
>
>
> ---------- Forwarded message ----------
> From: Joachim Breitner <mail at joachim-breitner.de>
> To: haskell-cafe at haskell.org
> Cc:
> Date: Mon, 07 Jan 2013 16:59:45 +0100
> Subject: Re: [Haskell-cafe] Example programs with ample use of deepseq?
> Hi,
> Am Montag, den 07.01.2013, 13:06 +0100 schrieb Joachim Breitner:
> > I’m wondering if the use of deepseq to avoid unwanted lazyness might be
> > a too large hammer in some use cases. Therefore, I’m looking for real
> > world programs with ample use of deepseq, and ideally easy ways to test
> > performance (so preferably no GUI applications).
>
> surprisingly, deepseq is not used as much as I thought.
> http://packdeps.haskellers.com/reverse/deepseq lists a lot of packages,
> but (after grepping through some of the code) most just define NFData
> instances and/or use it in tests, but rarely in the „real“ code. For
> some reason I expected it to be in more widespread use.
>
> But therefore I am even more interested in non-hackaged applications
> that I can be allowed to stud – in return I might be able to tell you
> way to speed up your application.
>
> Greetings,
> Joachim
>
> --
> Joachim "nomeata" Breitner
>   mail at joachim-breitner.de  |  nomeata at debian.org  |  GPG: 0x4743206C
>   xmpp: nomeata at joachim-breitner.de | http://www.joachim-breitner.de/
>
>
>
> ---------- Forwarded message ----------
> From: Johan Tibell <johan.tibell at gmail.com>
> To: Joachim Breitner <mail at joachim-breitner.de>
> Cc: Haskell Cafe <haskell-cafe at haskell.org>
> Date: Mon, 7 Jan 2013 08:12:31 -0800
> Subject: Re: [Haskell-cafe] Example programs with ample use of deepseq?
> On Mon, Jan 7, 2013 at 4:06 AM, Joachim Breitner
> <mail at joachim-breitner.de> wrote:
> > I’m wondering if the use of deepseq to avoid unwanted lazyness might be
> > a too large hammer in some use cases. Therefore, I’m looking for real
> > world programs with ample use of deepseq, and ideally easy ways to test
> > performance (so preferably no GUI applications).
>
> I never use deepseq, except when setting up benchmark data where it's
> a convenient way to make sure that the data is evaluated before the
> benchmark is run.
>
> When removing space leaks you want to avoid creating the thunks in the
> first place, not remove them after the fact. Consider a leak caused by
> a list of N thunks. Even if you deepseq that list to eventually remove
> those thunks, you won't lower your peak memory usage if the list was
> materialized at some point.
>
> In addition, by not creating the thunks in the first place you avoid
> some allocation costs.
>
> -- Johan
>
>
>
>
> ---------- Forwarded message ----------
> From: Peter Simons <simons at cryp.to>
> To: haskell-cafe at haskell.org
> Cc: gtk2hs-devel at lists.sourceforge.net
> Date: Mon, 07 Jan 2013 19:25:22 +0100
> Subject: Re: [Haskell-cafe] Announce: Leksah 0.13.1 (a bit experimental)
> Hi Hamish,
>
> would it be possible to get an update for process-leksah that works with
> recent versions of the 'filepath' package? I cannot build leksah-server
> with GCC 7.4.2 because of this issue.
>
> Take care,
> Peter
>
>
>
>
>
> ---------- Forwarded message ----------
> From: Hamish Mackenzie <hamish.k.mackenzie at gmail.com>
> To: Peter Simons <simons at cryp.to>
> Cc: gtk2hs-devel at lists.sourceforge.net, haskell-cafe at haskell.org
> Date: Tue, 8 Jan 2013 14:05:08 +1300
> Subject: Re: [Haskell-cafe] Announce: Leksah 0.13.1 (a bit experimental)
> Features in process-leksah have been merged into process.  For
> newer versions of GHC leksah-server just depends on process.
>
> If it is trying to install process-leksah then something else
> has probably gone wrong.
>
> Check "ghc-pkg list" for old versions of leksah.  Make sure
> you have the latest versions of ltk, leksah and leksah-server
> from github.  (if you use cabal-meta they will be in
> the "leksah/vendor" subdirectory).
>
> Here are the steps for installing from scratch...
> https://github.com/leksah/leksah/blob/master/.travis.yml
>
> Here is what it should look like when it installs...
> https://travis-ci.org/leksah/leksah
>
> On 8 Jan 2013, at 07:25, Peter Simons <simons at cryp.to> wrote:
>
> > Hi Hamish,
> >
> > would it be possible to get an update for process-leksah that works with
> > recent versions of the 'filepath' package? I cannot build leksah-server
> > with GCC 7.4.2 because of this issue.
> >
> > Take care,
> > Peter
> >
> >
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-- 
Yuriy Solodkyy
(y.solodkyy at gmail.com)
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