From treumann@XXXXXXXXXX Wed Jan 9 17:17:13 2008 Delivered-To: mpifrm-mpi-21-outgoing@XXXXXXXXXXXXXXXXXXXXXXX X-Original-To: mpifrm-mpi-21@XXXXXXXXXXXXXXXXXXXXXXX Delivered-To: mpifrm-mpi-21@XXXXXXXXXXXXXXXXXXXXXXX In-Reply-To: <1199919096.3138.56.camel@XXXXXXXXXXXXXXXXXXXXX> Subject: RE: [mpi-21] Proposal EH2: add const keyword to the C bindings To: mpi-21@XXXXXXXXXXXXX X-Mailer: Lotus Notes Release 7.0 HF277 June 21, 2006 From: Richard Treumann Date: Wed, 9 Jan 2008 18:16:29 -0500 X-MIMETrack: Serialize by Router on D01ML064/01/M/IBM(Release 7.0.2FP2 IGS702FP2HF5|November 8, 2007) at 01/09/2008 18:16:32 MIME-Version: 1.0 Content-type: multipart/alternative; Boundary="0__=0ABBF958DFECA8568f9e8a93df938690918c0ABBF958DFECA856" Content-Disposition: inline X-Virus-Scanned: by amavisd-new-20030616-p10 (Debian) at mailbouncer.mcs.anl.gov Sender: owner-mpi-21@XXXXXXXXXXXXX Precedence: bulk Reply-To: mpi-21@XXXXXXXXXXXXX X-Virus-Scanned: by amavisd-new-20030616-p10 (Debian) at mailbouncer.mcs.anl.gov X-Spam-Status: No, hits=-0.4 tagged_above=-1.0 required=5.3 tests=AWL, BAYES_00, HTML_10_20, HTML_MESSAGE X-Spam-Level: --0__=0ABBF958DFECA8568f9e8a93df938690918c0ABBF958DFECA856 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: quoted-printable If the "subset of processes within a communicator" is reasonably stable= you can do better by making an additional communicator containing only thos= e processes and doing MPI_Bcast on this subset communicator. If the subse= t keeps changing then making the subset communicator may be too costly compared to the savings. Dick Treumann - MPI Team/TCEM IBM Systems & Technology Group Dept 0lva / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601 Tele (845) 433-7846 Fax (845) 433-8363 owner-mpi-21@mpi-forum.org wrote on 01/09/2008 05:51:36 PM: > > It will affect the performance of my code to fix it. The pattern I ha= ve > here is that I'm sending the same buffer to a subset of the processes= > within a communicator. If this restriction is lifted, I can do that w= ith > a bunch of MPI_Isends to the various processes followed by a > MPI_Waitall. To fix this code, I need to either clone the buffer N ti= mes > (ouch!) or do N MPI_Sends in succession. > = --0__=0ABBF958DFECA8568f9e8a93df938690918c0ABBF958DFECA856 Content-type: text/html; charset=US-ASCII Content-Disposition: inline Content-transfer-encoding: quoted-printable

If the "subset of processes within a communicator" is reas= onably stable you can do better by making an additional communicator co= ntaining only those processes and doing MPI_Bcast on this subset commun= icator. If the subset keeps changing then making the subset communicato= r may be too costly compared to the savings.

Dick Treumann - MPI Team/TCEM
IBM Systems & Technology Group
Dept 0lva / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601
Tele (845) 433-7846 Fax (845) 433-8363


owner-mpi-21@mpi-forum.org wrote on 01/09/2008 05:51:36 PM:


>
> It will affect the performance of my code to fix it. The pattern I= have
> here is that I'm sending the same buffer to a subset of the proces= ses
> within a communicator. If this restriction is lifted, I can do tha= t with
> a bunch of MPI_Isends to the various processes followed by a
> MPI_Waitall. To fix this code, I need to either clone the buffer N= times
> (ouch!) or do N MPI_Sends in succession.
>

= --0__=0ABBF958DFECA8568f9e8a93df938690918c0ABBF958DFECA856--