Randomly different nlXC values
Posted: Tue Mar 21, 2023 11:46 am
Dear Yambo users and developers,
While converging the GW parameters of a 2D system, a colleague of mine and I encountered some weird behaviour. We realised that something was wrong in the calculation of the exchange part of the self-energy as it was changing from one calculation to the other in an unpredictable way. By this, I mean that sometimes the bottom conduction (band 57) changed, sometimes the top valence (56), sometimes both, and most importantly they changed when they were not supposed to: for example while converging the Sigma_c parameters, or while changing uniquely the number of parallelisation threads and even when two identical calculations were run with the very same command. Attached to my message, I add the reports of the latter example: the very same calculation, parallelised over the same number of threads, gives different values of nlXC. I have to specify that the two runs have been launched in two separate folders to prevent messing with the databases.
Have you ever encountered issues of this kind?
Any idea how to solve it?
To our experience, it looks like there's a problem in the parallelization of the nlXC algorithm, possibly while reading or writing the databases. I'm working with yambo 5.0.4 compiled in OpenMP.
Is there some known issue with compilation flags that may be responsible of this behaviour?
Is the MPI version more stable and reliable?
Is it a known bug?
Many thanks for your help
Cheers!
While converging the GW parameters of a 2D system, a colleague of mine and I encountered some weird behaviour. We realised that something was wrong in the calculation of the exchange part of the self-energy as it was changing from one calculation to the other in an unpredictable way. By this, I mean that sometimes the bottom conduction (band 57) changed, sometimes the top valence (56), sometimes both, and most importantly they changed when they were not supposed to: for example while converging the Sigma_c parameters, or while changing uniquely the number of parallelisation threads and even when two identical calculations were run with the very same command. Attached to my message, I add the reports of the latter example: the very same calculation, parallelised over the same number of threads, gives different values of nlXC. I have to specify that the two runs have been launched in two separate folders to prevent messing with the databases.
Have you ever encountered issues of this kind?
Any idea how to solve it?
To our experience, it looks like there's a problem in the parallelization of the nlXC algorithm, possibly while reading or writing the databases. I'm working with yambo 5.0.4 compiled in OpenMP.
Is there some known issue with compilation flags that may be responsible of this behaviour?
Is the MPI version more stable and reliable?
Is it a known bug?
Many thanks for your help
Cheers!