Re: [imp-dev] A note on the different implementations of IValueFactory

[Jurgen Vinju <jurgen@xxxxxxxxx>]

Hi Bob,

I wouldn't put a header on, because de-serialization gets a factory as
a parameter.
It's easy and safe to construct a value using one factory, and then
serialize it and
then de-serialize it using another. I wouldn't want to loose that looseness.

I thought about a field in each value, but the overhead is way too
big. Some (expensive) checks in each method of each factory would
prevent problems too.
Not a good idea either.

I suspect that using some "double dispatching" tricks we could have
each method in each value class degenerate to the reference
implementation. This puts a larger implementation and maintenance
burden on the factory implementations though...

What's the run-time cost of a class annotation and checking it at run-time?

Cheers,

Jurgen

On Tue, Jun 2, 2009 at 4:52 AM, Robert M. Fuhrer <rfuhrer@xxxxxxxxxxxxxx> wrote:
> Thanks, Jurgen, for merging in the contributions, and THANKS!!! Arnold for
> the contributions!!! These are sorely needed improvements!
>
> As to the compatibility issue, how about putting some sort of a haeder on
> the serialization format to avoid the more subtle mix-and-match errors?
>
> On Jun 1, 2009, at 2:53 PM, Jurgen Vinju wrote:
>
>> Dear imps,
>>
>> I've merged the contributions of Arnold Lankamp (CQ 3288) to
>> org.eclipse.imp.pdb.values. This includes the
>> binary streamable (de)serialization format for values and two
>> implementations of IValueFactory
>> and respective implementations of IValue and friends.
>>
>> Note that values constructed from/by different IValueFactories are not
>> to be mixed. We currently
>> do not cater for this in any of the implementations. It wasn't one of
>> our design decisions either to
>> have such a feature (point to ponder).
>>
>> Caution advised! Mixing values from different factories is quite an
>> easy pit to fall into.
>> Common symptoms {sh,c,w}ould be:
>>  - ClassCastExceptions
>>  - surprising inequalities between values (also with the isEqual() method)
>>  - surprising double occurring elements in sets or tuples in
>> relations or keys in maps (caused by previous point)
>>
>> Nevertheless, the two new factories improve performance dramatically
>> as compared to the reference implementation
>> of IValueFactory. Pdb.fast is the current high speed champion in most
>> of the tested analyses that deal with relations
>> and pdb.shared wins for analyses that deal with trees a lot.
>
> --
> Cheers,
>  - Bob
> -------------------------------------------------
> Robert M. Fuhrer
> Research Staff Member
> Programming Technologies Dept.
> IBM T.J. Watson Research Center
>
> IMP Project Lead (http://www.eclipse.org/imp)
> X10: Productivity for High-Performance Parallel Programming
> (http://x10.sf.net)
>
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