[racket-dev] [plt] Push #27446: master branch updated

We discussed this idea early on -- based on work by Casey and Robby and our own reasoning -- and I am pretty sure it was on your list. If it is not there, we should bring it in quickly. This should improve performance quite a bit. -- Matthias



On Sep 10, 2013, at 4:59 AM, Sam Tobin-Hochstadt wrote:

> I implemented what I thought would do this a long time ago, so if it isn't there then I must be misremembering or things have changed in the code to make it not happen.
> 
> Sam
> 
> On Sep 9, 2013 9:13 PM, "Eric Dobson" <eric.n.dobson at gmail.com> wrote:
> When did you add this? Last time I checked (June-ish) this was not
> added. Can you point to the code that does it?
> 
> On Mon, Sep 9, 2013 at 5:55 PM, Sam Tobin-Hochstadt
> <samth at cs.indiana.edu> wrote:
> > Not only did our own Sam write about this, but he thought that he changed
> > Typed Racket to do this. Am I missing something here, or are you describing
> > more optimization than we do already or ...?
> >
> > Sam
> >
> > On Sep 9, 2013 8:33 PM, "Robby Findler" <robby at eecs.northwestern.edu> wrote:
> >>
> >> FWIW, this is something that's been studied in small calculi in the
> >> literature. Nothing that will have to get thru all of the little details
> >> that you have to get right to make it work in a real language design like
> >> TR, but maybe you'll find some useful ways to look at the problem. (Mostly
> >> the papers I'm thinking of have Jeremy Siek as a co-author but there are
> >> others, including our own Sam.)
> >>
> >> Robby
> >>
> >>
> >> On Mon, Sep 9, 2013 at 7:14 PM, Eric Dobson <eric.n.dobson at gmail.com>
> >> wrote:
> >>>
> >>> I have ideas to remove about the contracts from TR code, but currently
> >>> that is only prototyped.
> >>>
> >>> Example:
> >>>
> >>> #lang typed/racket
> >>> (provide f)
> >>> (: f (Number -> Number))
> >>> (define (f x) x)
> >>>
> >>> Currently f is exported with the contract (number? . -> . number?),
> >>> but this can be safely reduced to (number . -> . any). This is because
> >>> the return value contract is checking things we have already ensured
> >>> statically. IIRC checking return values of functions is much more
> >>> expensive than just arguments, so this should reduce the cost of TR
> >>> boundary cost, but I don't have any numbers.
> >>>
> >>> On Mon, Sep 9, 2013 at 10:57 AM, Sam Tobin-Hochstadt
> >>> <samth at cs.indiana.edu> wrote:
> >>> > On Mon, Sep 9, 2013 at 11:35 AM, Neil Toronto <neil.toronto at gmail.com>
> >>> > wrote:
> >>> >> Nice, and thanks for the explanation. Just to make sure I get it: does
> >>> >> this
> >>> >> mean fully expanded TR modules are smaller?
> >>> >
> >>> > Yes.
> >>> >
> >>> >> Does it reduce the number of generated contracts?
> >>> >
> >>> > No.
> >>> >
> >>> >>
> >>> >>
> >>> >> On 09/08/2013 12:24 PM, Sam Tobin-Hochstadt wrote:
> >>> >>>
> >>> >>> Typed Racket has to expand into code that registers the type of each
> >>> >>> module-top-level identifier in the global environment so that other
> >>> >>> modules can find the types to typecheck with.  For example, this
> >>> >>> program:
> >>> >>>
> >>> >>> #lang typed/racket
> >>> >>> (provide x)
> >>> >>> (define: x : Integer 1)
> >>> >>>
> >>> >>> expands into (greatly simplified):
> >>> >>>
> >>> >>> #lang ...
> >>> >>> (#%provide x)
> >>> >>> (begin-for-syntax
> >>> >>>    (declare #'x Integer-rep))
> >>> >>> (define-values (x) 1)
> >>> >>>
> >>> >>> but what is `Integer-rep`?  It needs to be an expression that
> >>> >>> _constructs_ the internal Typed Racket representation of the
> >>> >>> `Integer`
> >>> >>> type. Previously, that looked something like this:
> >>> >>>
> >>> >>>      (make-Union (sort (list Negative-Fixnum-rep Positive-Fixnum-rep
> >>> >>> ...)))
> >>> >>>
> >>> >>> and so on and so forth for the components, all the way down to base
> >>> >>> types.  You can imagine how this gets quite large, especially for
> >>> >>> large types.
> >>> >>>
> >>> >>> However, this is wasteful, because every Typed Racket program, at
> >>> >>> type
> >>> >>> checking time, defines a constant that's the representation of the
> >>> >>> `Integer` type, right here [1]. So instead of serializing an
> >>> >>> expression that constructs the same thing as `-Int`, we can just
> >>> >>> *reference* `-Int` in the expanded code.  To make that possible,
> >>> >>> Typed
> >>> >>> Racket now builds a hash table [2] mapping types (really, their
> >>> >>> representations) to identifiers that denote those types. Then the
> >>> >>> serializer just consults this table [3].
> >>> >>>
> >>> >>> It turns out that base types (but no others) already used basically
> >>> >>> this mechanism, by storing the identifier *in* the type
> >>> >>> representation.  But that's now obsolete, and thus was removed in my
> >>> >>> subsequent commit.
> >>> >>>
> >>> >>> As a result, the type serialization is much smaller.
> >>> >>>
> >>> >>> [1]
> >>> >>>
> >>> >>> https://github.com/plt/racket/blob/master/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/numeric-tower.rkt#L107
> >>> >>> [2]
> >>> >>>
> >>> >>> https://github.com/plt/racket/blob/master/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/base-abbrev.rkt#L23
> >>> >>> [3]
> >>> >>>
> >>> >>> https://github.com/plt/racket/blob/master/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/env/init-envs.rkt#L51
> >>> >>>
> >>> >>> On Sat, Sep 7, 2013 at 3:20 PM, Neil Toronto <neil.toronto at gmail.com>
> >>> >>> wrote:
> >>> >>>>
> >>> >>>> On 09/06/2013 04:14 PM, samth at racket-lang.org wrote:
> >>> >>>>>
> >>> >>>>>
> >>> >>>>> 56b372c Sam Tobin-Hochstadt <samth at racket-lang.org> 2013-09-06
> >>> >>>>> 14:22
> >>> >>>>> :
> >>> >>>>> | Remember types that are defined, and use them in serialization.
> >>> >>>>> |
> >>> >>>>> | This extends a facility already available for base types,
> >>> >>>>> | making that facility no longer strictly needed.
> >>> >>>>> |
> >>> >>>>> | Shrinks the zo size for the `math` package by almost 1MB.
> >>> >>>>> :
> >>> >>>>>     M .../typed-racket/env/init-envs.rkt                |   1 +
> >>> >>>>>     M .../typed-racket/typecheck/def-export.rkt         |   7 +-
> >>> >>>>>     M .../typed-racket/typecheck/tc-toplevel.rkt        |  31
> >>> >>>>> +++---
> >>> >>>>>     M .../typed-racket/types/abbrev.rkt                 |  36
> >>> >>>>> +++----
> >>> >>>>>     M .../typed-racket/types/base-abbrev.rkt            |  12 ++-
> >>> >>>>>     M .../typed-racket/types/numeric-tower.rkt          | 108
> >>> >>>>> +++++++++----------
> >>> >>>>
> >>> >>>>
> >>> >>>>
> >>> >>>> Would you mind explaining this a little more? It sounds interesting,
> >>> >>>> and
> >>> >>>> the
> >>> >>>> commit almost has my name in it. :)
> >>> >>>>
> >>> >>>> Neil ⊥
> >>> >>>>
> >>> >>
> >>> >
> >>> > _________________________
> >>> >   Racket Developers list:
> >>> >   http://lists.racket-lang.org/dev
> >>>
> >>> _________________________
> >>>   Racket Developers list:
> >>>   http://lists.racket-lang.org/dev
> >>
> >>
> >
> _________________________
>  Racket Developers list:
>  http://lists.racket-lang.org/dev

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