Closed vanadiuz closed 4 years ago
Thanks for the response to the survey.
What exactly is the system in which you have a factor of 10 between running on a GPU or a CPU?
Against how many MPI processes are you comparing?
The mentioned factor of 2-3 was for an LB simulation on 8 MPI processes.
Dear Rudolf,
In my case, such a small performance was due to the fact that I used Dip. Direct Sum on CPU in the simulation, with which MPI does not work. Therefore, it was only one process. I apologize for the slurred presentation of my experience.
Without dip. direct sum on eight MPI processes, performance is indeed about only two times slower.
Once again, I carefully read your letter "Future of GPU support in Espresso". In case, when the double-precision dip. direct sum will be MPI-parallelized on the CPU, I will have no argument left supporting the benefit of the GPU.
Thank you, Vania
Dear developers,
I didn't find a dedicated email address to write about it, so I write here.
GPU support is one of the main Espresso's superpower:
ca. 60000, 10% out of them are dipolar
10%
Dip. P3M (with DLC) or Dip. Direct Sum on GPU + Lattice Boltzmann (GPU)+ WCA + FENE + Harmonic bonds
Potentially needed
~8e5
~1k
The ability to use GPU changes the whole game. Simulations work (could be sometimes) at least 10 times faster (not 2-3 times, as stated). Also Dip. Direct Sum on CPU does not support MPI.
mostly gtx1080ti (~70 GPUs) and several gtx2080ti.
Also
Lattis Boltzmann for box 100x100x100 eats about 300 MB of GPU memory (which usually has about 8 GB). So, having 20 cores and 1 GPU, I can run 20 simulations (1sim. for 1 core) and almost fully load my single GPU.
Best regards, Vania