Re: [Boost-users] does Boost.MultiArray work with Boost.MPI?

Subject: Re: [Boost-users] does Boost.MultiArray work with Boost.MPI?
From: John Phillips (phillips_at_[hidden])
Date: 2008-10-24 14:56:58

Tom Smith wrote:
> Dear All,
> 
> I am trying to write some parallel code using Boost.MPI? I also want to 
> use the class Boost.MultiArray.
> 
> My question is: does Boost.MultiArray support parallel computation?  If 
> not, which class should I use instead for multi-d array operations. 
> Thanks a lot!
> 
> best wishes
> 
> Tom
> 
> 
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   Tom,

   The answer appears to be no. For a custom class to be usable with the 
boost.MPI communication functions, it needs to have serialization 
operations defined (as in the serialization library). I looked in the 
MultiArray, Serialization, and MPI libraries, and I don't see such a 
definition in any of them. (It's always possible I missed it, and if the 
authors write back to tell you it is there, they are obviously right.)

   From this position, there are a few choices.

1 -- You could work with the authors to produce serialization operations 
for the multi-array library. This would be great, because it could get 
added to the trunk, tested and become a standard part of the MultiArray 
library that everyone else could also benefit from. If you are already 
familiar with both serialization and MultiArray, this might not even be 
very hard.

2 -- You could use the base MPI functions for a custom data structure. 
You still have complete access to the base MPI calls when working with 
boost.MPI. They include functions for serializing custom data 
structures. The functions aren't pretty by the standards of current C++ 
design, but they are there and functional. This would be a solution for 
your code, but less portable and less readable than option 1.

3 -- You could fall back to some other data structure for the data 
points. You could, for example, map your array to a vector and store it 
that way. Vectors already have provided serialization, so MPI 
communication is easy. The problem in that case is that the data 
structure may not be a good reflection of the concept it is supposed to 
model. This would complicate algorithms, and could cause problems with 
performance if it breaks things like data locality. Replacing the 
MultiArray with other data structures may also be possible, but it is 
probably not a good idea if it breaks much of your other reasoning.

   Sorry you are stuck with choices. Personally, I'd vote for option 1, 
but you should do what's best for your project.

                        John