Christian,
one explanation could be that the benchmark is memory bound, so running
on more sockets means higher memory bandwidth means better performance.
an other explanation is that on one node, you are running one openmp
thread per mpi task, and on 8 nodes, you are running 8 openmp threads
per tasks
Cheers,
Gilles
On 7/22/2015 4:42 PM, Crisitan RUIZ wrote:
Sorry, I've just discovered that I was using the wrong command to run
on 8 machines. I have to get rid of the "-np 8"
So, I corrected the command and I used:
mpirun --machinefile machine_mpi_bug.txt --mca btl self,sm,tcp
--allow-run-as-root mg.C.8
And got these results
8 cores:
Mop/s total = 19368.43
8 machines
Mop/s total = 96094.35
Why is the performance of mult-node almost 4 times better than
multi-core? Is this normal behavior?
On 07/22/2015 09:19 AM, Crisitan RUIZ wrote:
Hello,
I'm running OpenMPI 1.8.5 on a cluster with the following
characteristics:
Each node is equipped with two Intel Xeon E5-2630v3 processors (with
8 cores each), 128 GB of RAM and a 10 Gigabit Ethernet adapter.
When I run the NAS benchmarks using 8 cores in the same machine, I'm
getting almost the same performance as using 8 machines running a mpi
process per machine.
I used the following commands:
for running multi-node:
mpirun -np 8 --machinefile machine_file.txt --mca btl self,sm,tcp
--allow-run-as-root mg.C.8
for running in with 8 cores:
mpirun -np 8 --mca btl self,sm,tcp --allow-run-as-root mg.C.8
I got the following results:
8 cores:
Mop/s total = 19368.43
8 machines:
Mop/s total = 19326.60
The results are similar for other benchmarks. Is this behavior
normal? I was expecting to see a better behavior using 8 cores given
that they use directly the memory to communicate.
Thank you,
Cristian
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