Re: [Boost-users] boost.MPI dynamic data structure error

Subject: Re: [Boost-users] boost.MPI dynamic data structure error
From: Matthias Troyer (troyer_at_[hidden])
Date: 2010-10-20 01:27:54

On 19 Oct 2010, at 17:39, Jack Bryan wrote:

> thanks
> 
> I have two problems so that I cannot use boost.MPI. 

Neither is a problem, as you'll see below.

> 
> I need to transfer data very frequently, and calling boost Serialization will increase overhead by system call. 
>    
>     Because every time I call mpi_send, the Serialization() needs to be called. 
> 
>    This will reduce bandwith on MPI systems.

Boost.MPI has been designed to deal with this. Look at the skeleton&content mechanism. If you're sending the same datastructure many times there will be no cost beyond the first send. See also Dave's nice article here: http://daveabrahams.com/2010/09/03/whats-so-cool-about-boost-mpi/

> 
> Does boost.MPI support dynamic-size vector Serialization ? 

Yes, definitely. It was designed for that and I doubt that you will see any performance penalty compared to a hand-written solution.

> 
> For example, 
> 
> I declare a 
> 
> class myDataS {
> 
> double data1;
> vector<double> dataVec; 
> 
> } myData;
> 
> This class is visible to all processors. 
> 
> In processor 1, I initialize  dataVec(mysize); // mysize is not visible to other processors except processor 1. 
> 
> 
> I use world.send() to send myData to processor 2 by Serialization() in the class myDataS .
> 
> Does the processor2 knows that how large the dataVec is ? and in processor2, in world.recv(), 
> if I use myData to receive the data from processor 1, how to make sure that all elements in the vector have been received ? 
> 

Yes, it does.

Matthias