error? in automatic determination of ntaupar in rpar calculations
Posted: Wed Mar 30, 2022 1:47 pm
I am performing an rpa calculation of a bulk metal in vasp 6.3 (one atom in the unit cell, k-point grid of 14x14x14) using the finite temperature, low scaling algorithm.
When not specifying nomegapar and ntaupar, I get the following output (note the choice of ntaupar, the required memory and the memory warning)):
The code runs through either because it actually ends up using less memory than anticipated (as suggested by the "maximum memory used" statement at the end of the OUTCAR) or because the calculations are run on 1/4 or a node and there actually IS more memory available - just that that should remain available for other jobs running on the same node.
There are 2 things though that I do not understand:
Katharina
When not specifying nomegapar and ntaupar, I get the following output (note the choice of ntaupar, the required memory and the memory warning)):
Code: Select all
NOMEGAPAR set to 8 based on MAXMEM
MEMORY estimate per rank in MB for (frequency): 13.78
Looking for optimal time points distribution:
NTAUPAR req. mB/rank(max) req. mb/rank(min)
8 7755.1 7385.8
4 8489.1 8084.8
2 9474.8 9023.6
1 10583.8 10079.8
[...]
| This job will probably crash, due to insufficient memory available. |
| Available memory per mpi rank: 7300 MB, required memory: 11818 MB. |
| Reducing NTAUPAR or using more computing nodes might solve this |
| problem. |
[...]
Maximum memory used (kb): 7204868.
There are 2 things though that I do not understand:
- Why does the memory usage INCREASE as ntaupar decreases (see output above)
- I was astonished about the memory warning as someone in my group had successfully performed the same calculation on a cluster with less memory using vasp 6.2 - without getting a warning. We checked his output and found that the code set NTAUPAR to 2 and NOMEGAPAR to 4. I set that manually and - voilà - the calculation ran through without a warning, giving also a lower total memory requirement, however using about 5% more computational time. Clearly, the reduced memory is consistent with point 1, but if it is really true that the memory requirement increases in this case as NTAUPAR decreases, then why does vasp choose the option that uses MOST memory, risking a crash due to too little memory, as suggested by the memory warning?
Katharina