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Subject: Re: [OMPI devel] RFC: Remove heterogeneous support
From: Nathan Hjelm (hjelmn_at_[hidden])
Date: 2014-04-28 13:51:37


On Mon, Apr 28, 2014 at 01:44:28PM -0400, George Bosilca wrote:
>
> On Apr 28, 2014, at 13:39 , Nathan Hjelm <hjelmn_at_[hidden]> wrote:
>
> > This part of the heterogeneous support being broken was my fault. I
> > fixed it in r31535. I will try to spend some time over the next month or
> > so fixing heterogeneous support in the one-sided code. Right now the
> > packed datatype representation will not work if sizeof (int) is not
> > consistent.
>
> We are consistently using length-aware types (uint32_t) which have the same length. However, I would guess that RMA has the same issue as the datatype H functions (where the remote displacement cannot be correctly computed because we only know the local byte-level displacement).

Currently, the displacement is computed on the remote side so as long as
the datatype functions in osc/base support heterogenous we should be
good there. Once I finish the optimizations for RDMA networks that may
no longer be the case. I will try to keep the heterogeneous case in mind
as I write this code.

> > Not sure if we ever claimed to support this case though.
>
> If there is need for conversion, I guess one will have to switch back to the pt2pt mode … mode we don’t have anymore.

The rdma component is more or less the pt2pt component right now. I am
working on re-adding direct RDMA (and atomic) support for a EuroMPI
poster. I don't do any of the header conversion at the moment but it
won't be hard to add.

-Nathan



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