Replica Exchange Acceptance Issue on Different GPUs

[Munazzah Ansari]

Dear Developers,

I am currently running REST2 simulations using GROMACS patched with PLUMED and have observed inconsistent replica exchange acceptance ratios across different GPU cards. Below are the details:

GPUs Used & Software Versions Used:

1. Tesla P100-PCIE : GROMACS 2022 patched with PLUMED 2.9.0

2. Ada RTX 6000 : GROMACS 2024 patched with PLUMED 2.9.3

3. GeForce RTX 3090 : GROMACS 2022 patched with PLUMED 2.9.0

With Tesla P100 an exchange frequency of 800, the acceptance ratio is around 40–50% for all replicas. While using Ada RTX 6000 card, the exchange frequency of replicas is 0, do not exchange. Only at a frequency of 1 does a replica exchange occur. Exchange frequency with GeForce RTX 3090 above 390, some replicas exchange while others do not. With frequencies below 390, the acceptance ratio is around 40–50% for all replicas.

Since the same simulation setup and input files are being used, I am not getting why the behavior differs significantly across GPUs and GROMACS/PLUMED versions.

Best regards,
Munazzah 

PhD student

[Giovanni Bussi]

Hello

I would suggest trying to take a diff of the log files in the different runs. It is possibile that some of the decisions taken automatically by gromacs affect the result. Incomplete list:

- different replicas have different PME grids

- neighbor list updates changes

Giovanni

Sent from my iPhone

On 29 Jul 2025, at 06:40, Munazzah Ansari <ansarimu...@gmail.com> wrote:



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