Dear amber forum,
I have in the last week been working with the QM/MM interface of the
amber programme and especially focussing with performing a QM/MM
simulation with orca as the external program.
I have had great success running with orca as external program on small
test systems for short simulations with sander running on multiple
processors through MPI and orca running on single core through num
threads = 1.
However, if I want to run any kind of multi processing the QM part of
the simulation crashes with the error
ORCA finished by error termination in orca_util
Calling Command: mpirun -np 2
/pdc/software/24.11/other/orca/6.1.0/orca_util_mpi orc_job orca_hostfile
orc_job
[file orca_tools/qcmsg.cpp, line 394]:
.... aborting the run
This in principle is not surprising if we take a quick look at the orca
documentation where it states:
Do not start the ORCA driver with mpirun!
I have tested and if I use ORCA the intended way, that is calling ORCA
with its full path followed by the input file it runs just fine on
multiple processors and therefore the fix for the amber call should be
quite simple: Remove the "mpirun -np #MPIprocessors" call when orca is
initiated.
I should not that this should not be a version dependent thing for orca
as I have found documentation all the way back in ORCA 3 (i.e.
documentation from 2015), stating that starting ORCA with mpirun will
make it crash.
I have tried to work around the issue by using a template file
(use_template =1) however sadly AMBER seems to read the nprocs flag and
will make ORCA run through mpirun, leading to the same error as if
initiated with AMBER input.
If anyone have found another workaround I am all ears, though I hope
this mail reaches a developer as the fix on paper should be rather
simple, though given my inexperience in development it could not be as
simple as I want it to be.
Best,
Anders Frederiksen
Postdoctoral researcher
KTH, department of Chemistry, Stockholm, Sweden.
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Received on Mon May 25 2026 - 07:00:02 PDT
