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QS_DM_LS

README.md

Quickstep Density Matrix Linear Scaling

Description

This is a single-point energy calculation using linear-scaling DFT.

For large systems the linear-scaling approach for solving Self-Consistent-Field equations will be much cheaper computationally than using standard DFT and allows scaling up to 1 million atoms for simple systems. The linear scaling cost results from the fact that the algorithm is based on an iteration on the density matrix. The cubically-scaling orthogonalisation step of standard Quickstep DFT using OT is avoided and the key operation is sparse matrix-matrix multiplications, which have a number of non-zero entries that scale linearly with system size. These are implemented efficiently in the DBCSR library.

The problem size can be tuned by the parameter NREP in the input file, whereby the number of atoms scales cubically with NREP.

Files Description

  • H2O-dft-ls.inp (NREP=6): H20 density functional theory linear scaling consisting of 20'736 atoms in a 59 cubic angstrom box (6'912 water molecules in total). An LDA functional is used with a DZVP MOLOPT basis set and a 300 Ry cut-off.
  • H2O-dft-ls.NREP4.inp: H20 density functional theory linear scaling consisting of 6'144 atoms in a 39 cubic angstrom box (2'048 water molecules in total). An LDA functional is used with a DZVP MOLOPT basis set and a 300 Ry cut-off.
  • H2O-dft-ls.NREP2.inp: H20 density functional theory linear scaling consisting of 6'144 atoms in a 39 cubic angstrom box (2'048 water molecules in total). An LDA functional is used with a DZVP MOLOPT basis set and a 300 Ry cut-off (a smaller version of the H2O-dft-ls benchmark, with NREP=2, meant to run on 1 node).
  • TiO2.inp
  • amorph.inp

Results

NREP=4

The best configurations are shown below. Click the links under "Detailed Results" to see more detail.

Machine Name Architecture Date SVN Revision Fastest time (s) Number of Cores Number of Threads Detailed Results
HECToR Cray XE6 16/1/2014 13196 98.256 65536 8 OMP threads per MPI task hector-h2o-dft-ls
ARCHER Cray XC30 8/1/2014 13473 28.476 49152 4 OMP threads per MPI task archer-h2o-dft-ls
Magnus Cray XC40 3/12/2014 14377 30.921 24576 2 OMP threads per MPI task magnus-h2o-dft-ls
Piz Daint Cray XC30 12/05/2015 15268 27.900 32768 2 OMP threads per MPI task, no GPU piz-daint-h2o-dft-ls
Cirrus SGI ICE XA 24/11/2016 17566 543.032 2016 2 OMP threads per MPI task cirrus-h2o-dft-ls
Noctua Cray CS500 25/09/2019 9f58d81 37.730 10240 10 OMP threads per MPI task noctua-h2o-dft-ls

Weak Scaling on Piz Daint, CSCS

Following results were obtained in the following conditions:

  • Date: 15th November 2019
  • CP2K version: version 7.0 (Development Version, git:78cea8eeebb25e459941d8a28d987c9990d92676)
  • DBCSR version: v2.0.0-rc9 (git:15fdaba855385f12db7599a6e69b51a7a4ce8a9a)
  • CP2K flags: omp libint fftw3 libxc elpa parallel scalapack acc pw_cuda xsmm dbcsr_acc max_contr=4
  • Machine: Piz Daint (GPU partition), CSCS
  • Slurm configuration: 2 MPI ranks per node, 12 OpenMP threads per MPI rank
  • The cell contents specify the runtime (grep 'CP2K ' output.out) in seconds, while the cells marked with an X crashed with out-of-memory errors, and the cells left empty weren't measured.
nodes / NREP NREP=1 NREP=2 NREP=3 NREP=4 NREP=6 NREP=8 NREP=9
1 node 7.4 60.3 X
2 nodes 7.4 35.0 269.4 X
4 nodes 9.9 22.7 149.8 X
6 nodes 12.1 19.7 113.0 X
8 nodes 11.4 16.4 90.2 253.4 X
12 nodes 15.5 21.7 71.5 193.8 X
16 nodes 15.5 20.8 61.5 159.2 X
24 nodes 22.0 24.7 51.8 130.2 X
32 nodes 15.9 20.4 42.8 101.8 352.9 X
36 nodes 21.9 25.6 44.0 99.8 333.0 X
48 nodes 24.5 34.1 42.0 84.1 277.9 X
64 nodes 24.9 29.0 40.4 79.7 257.5 X
128 nodes 26.3 32.8 36.6 62.5 181.9 400.6 X
nodes / NREP NREP=6 NREP=8 NREP=9 NREP=10 NREP=11 NREP=12 NREP=13 NREP=14 NREP=16 NREP=18 NREP=19 NREP=20
256 nodes 132.6 262.3 359.2 498.8 647.1 X
512 nodes 106.0 212.5 290.2 409.2 534.0 732.3 875.2 1030.1 X
1024 nodes 98.1 168.9 284.7 510.8 786.5 1161.1 1607.3 1872.8 X