Re: [OMPI users] choosing network: infiniband vs. ethernet

[Jeff Squyres (jsquyres) via users]

Woo hoo!  I love getting emails like this.  We actually spend quite a bit of 
time in the design and implementation of the configure/build system so that it 
will "just work" in a wide variety of situations.

Thanks!


On Jul 17, 2020, at 5:43 PM, John Duffy via users 
mailto:users@lists.open-mpi.org>> wrote:

Hi Lana

I’m a Open MPI newbie too, but I managed to build Open MPI 4.0.4 quite easily 
on Ubuntu 20.04 just following the instructions in README/INSTALL in the top 
level source directory, namely:

mkdir build
cd build
../configure CFLAGS=“-O3”  # My CFLAGS
make all
sudo make all
sudo make install

It just worked. My small cluster happily runs Open MPI over TCP/1GB Ethernet.

The make install step installed everything into /usr/local. I did forget to 
ldconfig initially, which confused me. Other than that it just worked.

John



--
Jeff Squyres
jsquy...@cisco.com

Re: [OMPI users] choosing network: infiniband vs. ethernet

[Jeff Squyres (jsquyres) via users]

On Jul 16, 2020, at 2:56 PM, Lana Deere via users 
mailto:users@lists.open-mpi.org>> wrote:

I am new to open mpi.  I built 4.0.4 on a CentOS7 machine and tried doing an 
mpirun of a small program compiled against openmpi.  It seems to have failed 
because my host does not have infiniband.  I can't seem to figure out how I 
should configure when I build so it will do what I want, namely use infiniband 
if there are IB HCAs on the system and otherwise use the ethernet on the system.

UCX is the underlying library that Mellanox/Nvidia prefers these days for use 
with MPI and InfiniBand.

Meaning: you should first install UCX and then build Open MPI with 
--with-ucx=/directory/of/ucx/installation.

We just hosted parts 1 and 2 of a seminar entitled "The ABCs of Open MPI" that 
covered topics like this.  Check out:

https://www.open-mpi.org/video/?category=general#abcs-of-open-mpi-part-1
and
https://www.open-mpi.org/video/?category=general#abcs-of-open-mpi-part-2

In particular, you might want to look at slides 28-42 in part 2 for a bunch of 
discussion about how Open MPI (by default) picks the underlying network / APIs 
to use, and then how you can override that if you want to.

--
Jeff Squyres
jsquy...@cisco.com