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Re: [lammps-users] Invalid compute ID in variable formula
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Re: [lammps-users] Invalid compute ID in variable formula

From: Steve Plimpton <sjplimp@...24...>
Date: Thu, 22 Jun 2017 07:41:31 -0600

Well, you can't expect to evaluate a variable
if a compute it uses has been deleted.

There is a variable delete command.  Or just
don't evaluate either the variable or compute.
LAMMPS won't give an error unless you
request they be evaluated.


On Thu, Jun 22, 2017 at 6:46 AM, Christophe Ortiz <christophe.ortiz@...4020...80...> wrote:
Dear LAMMPS users,

I am using CNA to determine where are defects after the cascade in bcc Fe.

To do so, I use the following after the cascade has taken place:

compute  cnatom  all  cna/atom  3.45

thermo_style custom step temp
run 0

# Determine which defects have a structure different than BCC (3)
variable cna atom "c_cnatom == 5"
group groupcna dynamic all var cna every 1
run 0

variable  nbdefects  equal  count(groupcna)
print "Number of defects = ${nbdefects}"

Since the cna calculation is quite computationally expensive, I remove these compute before I continue other calculations.

uncompute cnatom

# other commands...

thermo_style custom step temp
run 1000

And there I get the following error:
ERROR: Invalid compute ID in variable formula (../variable.cpp:1257)

I understand why this occurs (because of the variable atom that is referenced) but I do not know how to solve it. Any idea?

Many thanks in advance and best regards,

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