[gmx-users] simulation uses only graphics card. None of the processor cores appears participated in simulation

[Mark Abraham]

Hi,


On Sun, Sep 18, 2016 at 7:21 PM Adarsh V. K. <adarsh_p130085bt at nitc.ac.in>
wrote:

> Dear Gromacs users,
>
> I installed CUDA tool kit 7.5 on Ubuntu 16.04. The PC is provided with an
> ASUS Graphics card, GTX 780Ti.
>
> While performing simulations the Gromacs uses only the graphics card.


This is physically impossible with current code. How do you think you are
assessing that? Tools like htop can be useful while the simulation is
running. Your md.log file reports the number of threads it runs on the
number of cores, which will obviously depend on how you built GROMACS, of
which version, and ran mdrun (which we don't know anything about, by the
way...) If you're doing a simple run with reaction field electrostatics,
then there's little for the CPU to do. But we don't know that either.


> It
> appears that none of the processor cores are used for simulation (8 core
> AMD FX 8350).
> The simulation completed in 30 minutes.
>
> ----------------------------------------
> I changed the graphics card to ASUS GT 710. Again the result is same. The
> simulation uses only graphics card. None of the processor cores
> participated simulation. The simulation completed in 3 hours.
>
> ------------------------------------------
> I tried simulation with out any supported graphics card. Simulation
> performed with  Processor core only. (8 core AMD FX 8350). The simulation
> completed in 1 hour 50 minutes.
> -------------------------------------------
> 1) How can I solve this problem?


The same PME simulation running about four times slower without the GPU
seems about right. But we have far too little information to even agree
that there is a problem :-)

Mark