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

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
>>
>> _________________________
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>>
>
>
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