QE 并行

最简单的并行参数

srun --mpi=pmi2 $EXE/pw.x -n 68 -nk 68 <relax.in> relax.out

上面是设置以68个核运行，k点被分到68个组中分别计算，相当于每个核管一个k点，QE说明书中对这几个参数的定义是

Quick estimate of parallelization parameters You need to know
- the number of k-points, Nk
- the third dimension of the (smooth) FFT grid, N3
- the number of Kohn-Sham states, M
These data allow to set bounds on parallelization:
- k-point parallelization is limited to Nk processor pools: -nk Nk
- FFT parallelization shouldn't exceed N3 processors, i.e. if you run with -nk Nk, use
N = Nk x N3 MPI processes at most (mpirun -np N ...)
- Unless M is a few hundreds or more, don't bother using linear-algebra parallelization

QE中设置k点并行还是很重要的，实测每个电子步至少加速一倍以上。