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Task #3031

evaluate the impact of particle order on PME

Added by Szilárd Páll 2 months ago. Updated about 1 month ago.

Status:
New
Priority:
Normal
Assignee:
-
Category:
mdrun
Target version:
Difficulty:
simple
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Description

The DD sorting does have an impact on PME performance, especially on GPUs. In current code this effect can be measured with single rank vs separate PME rank runs.
This impact should be evaluated across a range of input sizes (possibly densities?).


Related issues

Related to GROMACS - Feature #2054: PME on GPUAccepted

History

#1 Updated by Szilárd Páll 2 months ago

#2 Updated by Jonathan Vincent 2 months ago

What is the change/patch that implements DD sorting?

I should look at this as well.

#3 Updated by Szilárd Páll 2 months ago

Jonathan Vincent wrote:

What is the change/patch that implements DD sorting?

This is not a new feature, any multi-rank run will do that.

#4 Updated by Jonathan Vincent about 1 month ago

Ran this with the water boxes using either 4 tMPI ranks (3 PP and 1 PME) or 2 tMPI ranks (1 PP and 1 PME). Uisng a seperate PME rank seemed the simplest way to get a result without DD.

                                  0.96    1.5    3       6       12     24     48      96      192    384    768     1536    3072
2019.2, 4 ranks, RTX 2080         6.055   7.344  11.436  17.398  33.652 62.915 107.11  204.226 397.89 765.08 1497.4  2860.3  5762.8
2019.2, 2 ranks, RTX 2080         5.991   7.345  11.492  17.531  32.667 61.885 117.638 237.982 476.64 941.64 1849.64 3502.3  6982.1
Master, 4 ranks, RTX 2080         7.2233  8.5901 11.1816 17.369  31.557 62.42  108.455 212.202 412.4  768.34 1505.26 2924.16 5918.74
Master, 2 ranks, RTX 2080         6.2285  7.4324 11.2968 17.487  30.904 62.122 118.11  241.019 477.51 942.31 1853.08 3516.2  7023.8

The differences are quite small for the smaller boxes, but become significant. The master git hash is 0c26c550ed55e12b77954dd0e8c5d956421ae501. Will look at other hardware as well. The difference becomes quite significant for larger sizes.

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