Hi Ludovic, This is in principle weird. The # of steps for SCF convergence should not depend on the blocksize. Could you provide some info on your compilation? Compiler, optimization flags, mpi and compilation flags for mpi compilation?
Marcos El 7 de sep de 2010, 10:23 a.m., "Ludovic Briquet" <[email protected]> escribió: Dear SIESTA users, I am in process of assessing how well the parallel version of SIESTA 2.0.2 performs on our new cluster. To do so, I'm runing test jobs and monitoring the timing of the jobs with different SIESTA and cluster-related inputs. The test job I'm running is a (1x2) Si(100) slab geometry optimisation. The system contains 64 atoms. Functional is PBE, mesh cutoff is 150 Ry, Kpoint mesh is 4x2x1. The basis set is setted as %Block PAO.Basis Si 3 -0.46385 n=3 0 2 E 15.42551 4.96988 7.00000 4.37722 1.00000 1.00000 n=3 1 2 E 4.69636 3.83128 7.00000 4.09123 1.00000 1.00000 n=3 2 1 E 11.96912 0.03131 4.55426 1.00000 %EndBlock PAO.Basis 1- When I don't specify any BlockSize, SIESTA use a defautl value of 24 and not 8 as stated in the user guide. Does anyone know the reason for that? 2- When trying different BlockSize options, I see that the scf convergence is not the same for all jobs. For exemple, for a 4 cpu job: BlockSize 8: total run time is 15h54 - first optimization step is completed with 205 scf iterations BlockSize 16: total run 16h22 - - first optimization step is completed with 222 scf iterations BlockSize 24: total run 13h15 - first optimization step is completed with 74 scf iterations BlockSize 32: total run 19h09 - first optimization step is completed with 399 scf iterations It should be noted that the energies at the end of the scf processes are all similar and the optimisation terminates in 34 steps for all jobs. I understood from the tutorial session in Santander last June that the compilation of SIESTA in parallel can be a very tricky business. So I was wandering if that scf behviour could in anyway be related to the compilation? Or is it just a normal behaviour of SIESTA? Cheers Ludovic
