Dear lammps-users,
Now I have several intel xeon processors e5 v4 with 280 cores. I find that the calculation speed is the fastest by using 54 cores when I use hybrid force field.
I still have a NVIDIA Tesla P100 GPU. When the force field is tersoff, the calculation speed tested by one GPU core and one CPU core is four times higher than the 28 CPU cores. But when the force field is hybrid, the calculation speed tested by one GPU and one CPU core is two times lower than the 28 CPU cores.
I don’t know how to use existing hardware to accelerate the calculation speed when my force field is hybrid. It’s OK if I should buy some more hardware. Could you please give me some suggestions? Thank you for your help in advance.
Yours sincerely
Shuting Wang
Dear lammps-users,
Now I have several intel xeon processors e5 v4 with 280 cores. I find that
the calculation speed is the fastest by using 54 cores when I use hybrid
force field.
I still have a NVIDIA Tesla P100 GPU. When the force field is tersoff, the
calculation speed tested by one GPU core and one CPU core is four times
higher than the 28 CPU cores. But when the force field is hybrid, the
calculation speed tested by one GPU and one CPU core is two times lower than
the 28 CPU cores.
that is because with a hybrid pair potential, you must compute the
neighbor lists on the CPU and then transfer it to the GPU, even if all
individual pair styles are GPU accelerated.
that will cause a significant slowdown, in your case, since you are
using only one CPU. you can try to minimize this by using multiple
CPUs with the same GPU, but the additional overhead of computing
neighbor lists on the CPU and transferring significant additional data
to the GPU cannot be completely avoided.
I don't know how to use existing hardware to accelerate the calculation
speed when my force field is hybrid. It's OK if I should buy some more
hardware. Could you please give me some suggestions? Thank you for your help
in advance.
the best way to get the most performance with the GPU package, is to
avoid a hybrid pair style.
there are also many other, simulation specific factors, that can
affect performance, where it is not possible to give general advice.
axel.
Dear lammps-users,
Thanks a lot to Axel Kohlmeyer. It’s very kind of you to reply me. I agree with your explanation about slow calculation speed caused by hybrid pair potential. Your suggestion about how to accelerate the calculation speed is very useful.
I have a new question now. I use the command "mpirun -n 1 lmp_mpi -sf gpu -pk gpu 1 < in.W " to calculate the thermal conductivity. But it indicates the ERROR : Cannot open EAM potential file eam/alloy. Here is my input script blew. Could anyone give me some suggestions? I don’t know what’s wrong with my input script. Thank you for your help in advance.
Best wishes.
Shuting Wang
Dear lammps-users,
Thanks a lot to Axel Kohlmeyer. It's very kind of you to reply me. I agree
with your explanation about slow calculation speed caused by hybrid pair
potential. Your suggestion about how to accelerate the calculation speed is
very useful.
I have a new question now. I use the command "mpirun -n 1 lmp_mpi -sf gpu
-pk gpu 1 < in.W " to calculate the thermal conductivity. But it indicates
the ERROR : Cannot open EAM potential file eam/alloy. Here is my input
script blew. Could anyone give me some suggestions? I don't know what's
wrong with my input script. Thank you for your help in advance.
the error message is self-explanatory. think about it.
axel.