[mvapich-discuss] mvapich compilation error with psm

[Hari Subramoni]

Hello Christof,

The "--disable-mcast" is a configure time option that enables/disables code
paths that support collective operations that take advantage of InfiniBand
hardware based multicast.

This option is "not" applicable to the PSM channel as the required support
is not available from the network hardware. Thus, by default, this should
be disabled for the PSM channel.

Hardware based multicast is a feature of the network adapter and not the
processor. Thus, KNL / Xeon should not make a difference.

Regards,
Hari.

On Dec 1, 2016 2:36 PM, "Christof Koehler" <
christof.koehler at bccms.uni-bremen.de> wrote:

Hello,

> In summary, we have run some tests on the setup you mention (KNL with
dual Omni-Path cards) and we have achieved nearly link speed by running
different osu_ benchmarks for bandwidth and message rates measurements and
using 4 ranks per node on a pair of nodes and not using any special build
flags.
> ./configure  --without-mpe --disable-mcast --enable-shared
--with-device=ch3:psm --with-psm2 --with-ch3-rank-bits=32
--disable-maintainer-mode

I have a question regarding compilation options. In the line above
"--disable-mcast" is set. This is also set for the patched mvapich 2.1
version Intel diistributes together with the OmniPath driver tarball.

However, running configure -h shows "--enable-mcast
enable hardware multicast" which would indicate to me that
"--disable-mcast" is the actual default.

The manual documents the "MV2_USE_MCAST" flag with a default value of
"0", so it should be disabled in any case ?

I am confused. Is the "--disable-mcast" flag recommended or required ?
Does it have an effect at all ?

I built our mvapich2 for psm2 without setting any flag regarding
mulitcast. On the other hand we do not have KNL hardware.


Best Regards

Christof



--
Dr. rer. nat. Christof Köhler       email: c.koehler at bccms.uni-bremen.de
Universitaet Bremen/ BCCMS          phone:  +49-(0)421-218-62334
Am Fallturm 1/ TAB/ Raum 3.12       fax: +49-(0)421-218-62770
28359 Bremen

PGP: http://www.bccms.uni-bremen.de/cms/people/c_koehler/

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