Dear All,
I have been trying to run Lammps in parallel for the first time. To be sure I cross checked the results with that of serial (by comparing diffusivities of the ion in water). System I am using is Na ion in water.
I am getting different answers from the serial and parallel computing.
Version of Lammps - lammps-8Jul-2013
Number of parallel processors - 12 node 24 processors
Parallel Computer used - Lonestar (TACC facility)
For serial Run I used 2 systems - my personal desktop and TACC facility.
Inputs were divided into 3 scripts. 1st to create an equilibrated system. 2nd and 3rd to generate equilibrated outputs.
I am attaching the data file and the input files. This was just a test run before I could run anything other. I have read that, eventhough theoretically both should be same, while restarting, the final results might diverge. But the error seems to be a bit high. The diffusivity values for the ion I got from Serial and Parallel are the following.
Serial from Desktop : 4.7974 *10^(-10) m^2/s
Serial from TACC : 1.6785 * 10^(-9) m^2/s
Parallel:1.2024 *10^(-9) m^2/s
Sorry for such a long email and input scripts. Question is whatever the system is, should i not expect the same answers (eventhough physically it may be bogus). Also while compiling TACC, it used -DLAMMPS_INT64_MAX where as my desktop did not take it. So I compiled with -DLAMMPS_SMALLSMALL. Any help would be greatly appreciated.
Regards
Vaidyanathan M S
Dept of Chemical Engg
The University of Texas at Austin
data_polwater.txt (58.7 KB)
input_polwater.txt (2.46 KB)
input_polwater2.txt (1.8 KB)
input_polwater3.txt (1.11 KB)