[lammps-users] Strange "Minimize" Command

I am sure that I set the following command:

“minimize 0 0 1000 1000”

and expect the calculation to run 1000 iterations.

But the calculation always finishes at 98 iteration and give me following information:

Step Temp E_pair E_mol TotEng Press
0 0 -14267.84 0 -14267.84 -313.70063
98 0 -14272.262 0 -14272.262 0.0017080182
Loop time of 106.375 on 1 procs for 98 steps with 3265 atoms

Minimization stats:
Stopping criterion = max force evaluations
Energy initial, next-to-last, final =
-14267.8395154 -14272.2617366 -14272.2617367
Force two-norm initial, final = 9.79841 0.000622057
Force max component initial, final = 0.344329 2.58589e-05
Final line search alpha, max atom move = 0.100534 2.59968e-06
Iterations, force evaluations = 98 1001

How so?

2008/10/27 Jarvis Chong <[email protected]>:

I am sure that I set the following command:

"minimize 0 0 1000 1000"

and expect the calculation to run 1000 iterations.

But the calculation always finishes at 98 iteration and give me following
information:

Step Temp E_pair E_mol TotEng Press
       0 0 -14267.84 0 -14267.84 -313.70063
      98 0 -14272.262 0 -14272.262 0.0017080182
Loop time of 106.375 on 1 procs for 98 steps with 3265 atoms
Minimization stats:
  Stopping criterion = max force evaluations
  Energy initial, next-to-last, final =
        -14267.8395154 -14272.2617366 -14272.2617367
  Force two-norm initial, final = 9.79841 0.000622057
  Force max component initial, final = 0.344329 2.58589e-05
  Final line search alpha, max atom move = 0.100534 2.59968e-06
  Iterations, force evaluations = 98 1001
How so?

Jarvis:

The minimize command

minimize A B C D

will terminate if either the maximum number of iterations (C) or the
maximum number of force evaluations (D) has been exceeded.

In this case, if you look at your output, you'll see that LAMMPS has
performed 1001 force evaluations, which is more than the 1000 you
called for in the script. That's why it stops after 98 iterations. (It
even tells you "stopping criterion = max force evaluations"!)

If you want to run longer, you have to increase D to compensate.

--AEI