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Touch up benchmarks/QS_low_scaling_postHF/README.md

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@ -17,31 +17,33 @@ correlation energy is calculated on top of a PBE SCF (without EXX).
## Reference timings
These benchmarks were run during the pilot phase of the LUMI-G supercomputer (December 2022), under
git commit d8f36242127b9a828f127550ecd9613eefb3f1cc. All calculations were run with 8 GPUs, 16 MPI
ranks, and 3 OMP threads per node. Note that this amounts to a total of 48 out of the 64 CPUs of a
LUMI-G node, because full nodes where not available at the time.
These benchmarks were run during the pilot phase of the
[LUMI-G supercomputer](https://docs.lumi-supercomputer.eu/hardware/compute/lumig/) (December 2022), under
[git commit d8f3624](https://github.com/cp2k/cp2k/commit/d8f36242127b9a828f127550ecd9613eefb3f1cc).
All calculations were run with 4 GPUs (8 GCDs), 16 MPI ranks, and 3 OMP threads per node.
Note that this amounts to a total of 48 out of the 64 CPUs of a LUMI-G node,
because full nodes where not available at the time.
### 32-H2O
| Input file | Wall time (s) on 2 nodes | Wall time (s) on 4 nodes |
| --------------------- | ------------------------ | ------------------------ |
| H2O-32-RPA-TZ.inp | 1530.767 | 788.375 |
| H2O-32-SOS-MP2-TZ.inp | 1787.164 | 917.736 |
| H2O-32-RPA-TZ.inp | 1531 | 788 |
| H2O-32-SOS-MP2-TZ.inp | 1787 | 918 |
### 64-H2O
| Input file | Wall time (s) on 8 nodes | Wall time (s) on 16 nodes |
| --------------------- | ------------------------ | ------------------------- |
| H2O-64-RPA-TZ.inp | 2570.453 | 1414.915 |
| H2O-64-SOS-MP2-TZ.inp | 2784.860 | 1505.283 |
| H2O-64-RPA-TZ.inp | 2570 | 1415 |
| H2O-64-SOS-MP2-TZ.inp | 2785 | 1505 |
### 128-H2O
| Input file | Wall time (s) on 32 nodes | Wall time (s) on 64 nodes |
| ---------------------- | ------------------------- | ------------------------- |
| H2O-128-RPA-TZ.inp | 3710.013 | 2577.737 |
| H2O-128-SOS-MP2-TZ.inp | 3701.663 | 2539.208 |
| H2O-128-RPA-TZ.inp | 3710 | 2578 |
| H2O-128-SOS-MP2-TZ.inp | 3702 | 2539 |
## Notes on parameter choice and performance
@ -55,11 +57,11 @@ Most input files use 4 as the value for MEMORY_CUT. This controls the batching p
tensor contractions such that the memory footprint remains limited. Note that using a high value for
this keyword leads to overheads. As an illustration, the H2O-128-RPA-TZ.inp input file with MEMORY_CUT
set to 3 does not run on 32 LUMI-G nodes because of memory. However, it runs on 64 nodes with a wall
time of 2149.162 seconds (compared to 2577.737 seconds with MEMORY_CUT set to 4).
time of 2149 seconds (compared to 2578 seconds with MEMORY_CUT set to 4).
Finally, the value of 6 was chosen for the MIN_BLOCK_SIZE keyword, while the default is 5. This is
a trade-off between better sparsity for smaller block size, and higher efficiency of block-wise
matrix-matrix mulitplications for larger sizes. This mostly matters for the force calculations of large
system, because the bottleneck of the calculation involves the contraction of fairly dense tensors.
The H2O-128-RPA-TZ.inp input file with MIN_BLOCK_SIZE 5 runs in 4104.855 seconds on 32 nodes, versus
3710.013 seconds with a block size of 6.
The H2O-128-RPA-TZ.inp input file with MIN_BLOCK_SIZE 5 runs in 4105 seconds on 32 nodes, versus
3710 seconds with a block size of 6.