[fpc-pascal] Acitve Object Messaging Library

Michael Van Canneyt michael at freepascal.org
Mon Apr 5 19:19:23 CEST 2010

On Mon, 5 Apr 2010, Werner Van Belle wrote:

> Michael Van Canneyt wrote:
>> Hello,
>> This looks promising.
>> Can you explain the similarities and differences with MPI ?
> That would require me to read up on what MPI is and honoustly, I'm not a
> big fan on doing that, certainly not after I went to their homepage and
> saw around 70 lines of contributing companies, all of them big names.
> If my guess is correct, MPI is similar to a CORBA IDL Specification (in
> general terms). If this undertsanding is correct then MPI has nothing to
> do with the Acrtive Objects as I present them. E.g: the active objects
> library cannot perform interprocess communication and certainly not
> accross different machines. It only deals with thread activation and
> deactivation at appropriate times. To do so, it uses a queue in which a
> normal stackframe is pushed and at a later time executed.

MPI is for passing messages between parallel running tasks. 
(the name means Message Passing Interface)
This is what Active Objects does.

To me, the difference seems that Active Objects runs within a single
process, and MPI allows to run the tasks in different processes, even
on different machines.

>> Several people have asked about MPI in Free Pascal. Maybe
>> this is an answer for them.
> People hoping that this is an MPI (in the sense of
> http://www.mcs.anl.gov/research/projects/mpi/) for pascal will be
> disappointed. Those who are looking for an alternative to thread based
> approaches to deal with multiple tasks in a single program might find
> this interesting.

It seems to me that there are more parallels between MPI and Active Objects
than you think. Both are tools for parallel (sic) computing, after all.


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