Fusion

[David Feuer]

Thank you! I will dig into using that ASAP now that I can understand the
directions.
On Aug 29, 2014 5:50 AM, "Simon Peyton Jones" <simonpj at microsoft.com> wrote:

> I have added a section "Ticky-ticky quick start" to our ticky-ticky
> profiling page, to explain how I go about dealing with the problem you
> describe
> https://ghc.haskell.org/trac/ghc/wiki/Debugging/TickyTicky
>
> Simon
>
> | -----Original Message-----
> | From: David Feuer [mailto:david.feuer at gmail.com]
> | Sent: 20 August 2014 09:33
> | To: Simon Peyton Jones
> | Subject: Re: Fusion
> |
> | I'll be happy to try to expand it with some examples. I'm wondering if
> | you could help me figure something out: the (simple) cons/build rule
> | we discussed, along with the similar cons/augment rule,
> |
> | "cons/build"    forall (x::a) (g::forall b . (a->b->b)->b->b) . x :
> | build g = build (\c n -> c x (g c n))
> | "cons/augment"  forall (x::a) (g::forall b . (a->b->b)->b->b)
> | (xs::[a]) . x : augment g xs = augment (\c n -> c x (g c n)) xs
> |
> | somehow *increase* allocation substantially (11.7%) in the "event"
> | NoFib test, and also significantly (3.6%) in constraints, somewhat
> | (2.4%) in nucleic2 [remember this] and 1.4% in ansi. I am having a
> | heck of a time trying to figure out how to track these down, and
> | burning loads of time recompiling GHC over and over again. On the flip
> | side of things, the wang test reduces allocation by 45.8% if I use
> | these rules (both of which fire), but only when I also use -fsimple-
> | list-literals for nofib/spectral/hartel/nucleic2/Main.hs.
> | nucleic2 still performs a little more allocation.
> |
> | On Wed, Aug 20, 2014 at 2:56 AM, Simon Peyton Jones
> | <simonpj at microsoft.com> wrote:
> | > Great start, thank you. Can I suggest that for each question you
> | give
> | > a concrete example?  Otherwise only experts, who already know a lot
> | about
> | > rules, will understand the question, let alone the answer.   I’d be
> | happy to
> | > take another look then.
> | >
> | >
> | > Simon
> | >
> | >
> | >
> | > From: David Feuer [mailto:david.feuer at gmail.com]
> | > Sent: 19 August 2014 23:30
> | > To: Simon Peyton Jones
> | > Cc: Haskell Libraries
> | > Subject: Re: Fusion
> | >
> | >
> | >
> | > I've started a page at
> | > https://ghc.haskell.org/trac/ghc/wiki/FoldrBuildNotes
> | > Please feel free to add, correct, etc.
> | >
> | > On Aug 19, 2014 3:10 AM, "Simon Peyton Jones"
> | <simonpj at microsoft.com> wrote:
> | >
> | > David
> | >
> | > You've been doing all this work on improving fusion, and you
> | probably
> | > have a very good idea now about how it works, and how GHC's
> | libraries
> | > use phases and RULES to achieve it. A kind of design pattern, if you
> | > like; tips and tricks.
> | >
> | > I wonder if you'd feel able to write a GHC wiki page describing what
> | > you have learned, with examples and explanation about why it is done
> | that way.
> | > If you did this, someone who follows in your footsteps wouldn't need
> | > to re-learn everything.  And maybe someone will say "oh, there's one
> | > pattern you have omitted, here it is".
> | >
> | > Thanks
> | >
> | > Simon
>
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