[racket] serialization of math/array

On Thu, Jul 24, 2014 at 7:21 AM, Berthold Bäuml <berthold.baeuml at dlr.de> wrote:
>> De-serializing an array of numbers and then passing it to typed code
>> would produce a wrapper, not a first-order check, and so would be very
>> expensive.
>
> Even when first-order checks would be possible the cost of such a check would be significant in our application. We wan to use serialization/deserialization to send data between programs -- when running on the same computer the I/O cost (local sockets) would be almost negligible.
>
> Would it be possible to have a typed serialization in the near future?

I think the Racket `serialize` API is likely to be higher-cost than
that, even without considering Typed Racket.

>> What you want is something that can tell that the untyped reference is
>> dead after value is passed to typed code, so that a first-order check
>> can be used. This would require something new from Racket in the form
>> of a revocable reference.
>
> Does this also hold for immutable arrays? In this case a first-order check should suffice in principle.

Yes, for immutable arrays represented as flat data (not functions) the
checks would not require wrappers.

Sam

> Berthold
>>
>
>>
>> On Wed, Jul 23, 2014 at 11:52 AM, Matthias Felleisen
>> <matthias at ccs.neu.edu> wrote:
>>>
>>> Let's assume we serialize arrays of numbers, which is what I assume the background to the question is. In that case, the answer isn't all that obvious to me.
>>>
>>>
>>>
>>>
>>> On Jul 23, 2014, at 11:47 AM, Sam Tobin-Hochstadt <samth at cs.indiana.edu> wrote:
>>>
>>>> That really depends what the contracts are, and if they're first-order.
>>>>
>>>> Sam
>>>>
>>>> On Wed, Jul 23, 2014 at 11:45 AM, Matthias Felleisen
>>>> <matthias at ccs.neu.edu> wrote:
>>>>>
>>>>> Will these costs dominate the cost of I/O here?
>>>>>
>>>>>
>>>>> On Jul 23, 2014, at 11:37 AM, Sam Tobin-Hochstadt <samth at cs.indiana.edu> wrote:
>>>>>
>>>>>> Unfortunately, I think that strategy would incur substantial overhead
>>>>>> for things like serialization of large arrays.
>>>>>>
>>>>>> Sam
>>>>>>
>>>>>> On Wed, Jul 23, 2014 at 11:28 AM, Matthias Felleisen
>>>>>> <matthias at ccs.neu.edu> wrote:
>>>>>>>
>>>>>>> On Jul 23, 2014, at 11:10 AM, Neil Toronto <neil.toronto at gmail.com> wrote:
>>>>>>>
>>>>>>>> On 07/16/2014 10:25 AM, Berthold Bäuml wrote:
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> will there be serialization support for math/array and math/matrix in the near future? As far as I understand in principle it should be possible at leas in  a straight forward way as there are  already the routines array->list and list->array.
>>>>>>>>
>>>>>>>> Sorry it's taken so long to reply. Part of the problem is that `racket/serialize` isn't typed:
>>>>>>>>
>>>>>>>> #lang typed/racket
>>>>>>>>
>>>>>>>>> (require racket/serialize)
>>>>>>>>> serialize
>>>>>>>> Type Checker: missing type for identifier;
>>>>>>>> consider using `require/typed' to import it
>>>>>>>> identifier: serialize
>>>>>>>> from module: racket/serialize in: serialize
>>>>>>>>
>>>>>>>>
>>>>>>>> This and the fact that the array struct types are declared in Typed Racket makes adding serialization tricky at best. Also, it would only work in untyped Racket.
>>>>>>>>
>>>>>>>> Generally, deserializing is hard to make type-safe, and nobody has taken it up yet for Typed Racket. Occurrence typing should help, but would require `deserialize` to take a predicate argument (like the second argument to `list*->array`), which it currently doesn't do.
>>>>>>>
>>>>>>>
>>>>>>> Lucky us. I often leave the I/O parts of my programs untyped (I write either highly imprecise unchecked signatures or I don't provide types).
>>>>>>> ____________________
>>>>>>> Racket Users list:
>>>>>>> http://lists.racket-lang.org/users
>>>>>
>>>
>>
>> ____________________
>>  Racket Users list:
>>  http://lists.racket-lang.org/users
>
> --
> -----------------------------------------------------------------------
> Berthold Bäuml -- Head of Autonomous Learning Robots Lab
> DLR, Robotics and Mechatronics Center (RMC)
> Münchner Str. 20, D-82234 Wessling
> Phone +49 8153 282489
> http://www.robotic.de/Berthold.Baeuml
>
>
>
> ____________________
>   Racket Users list:
>   http://lists.racket-lang.org/users