Re: [Boost-users] [EXTERNAL] Boost MPI Collective

Subject: Re: [Boost-users] [EXTERNAL] Boost MPI Collective
From: Belcourt, Kenneth (kbelco_at_[hidden])
Date: 2014-09-01 23:11:25

On Aug 25, 2014, at 9:59 AM, Nolen, Steven Douglas <drnuke_at_[hidden]> wrote:

> In boost/mpi/collectives/reduce.hpp
> The template function specialization for reduce-ing a std::vector, should probably be modified.
>  
> From
>  
> template<typename T, typename Op>
> void
> reduce(const communicator & comm, std::vector<T> const & in_values,
>        std::vector<T> & out_values, Op op, int root)
> {
>   out_values.resize(in_values.size());
>   reduce(comm, &in_values.front(), in_values.size(), &out_values.front(), op,
>          root);
> }
>  
> To
>  
> template<typename T, typename Op>
> void
> reduce(const communicator & comm, std::vector<T> const & in_values,
>        std::vector<T> & out_values, Op op, int root)
> {
>   if( comm.rank() == root ) out_values.resize(in_values.size());
>   reduce(comm, &in_values.front(), in_values.size(), &out_values.front(), op,
>          root);
> }
>  
> This will save an extraneous allocation on the non-root nodes.

Hi Steve,

This change looks reasonable, I just committed it, thanks for pointing it out.  

— Noel