Gaussian

module avail g03/
module avail g09/
module avail g16/

Gaussian is a package of quantum mechanics programs. The program serves to predict the energies, molecular structures, and vibrational frequencies of molecular systems, along with numerous molecular properties derived from these basic computation types.

License

Gaussian 03 and Gaussian 09 can be used on the clusters installed in Brno location:

-l select=1:ncpus=N: ... :brno=True

The license for Gaussian 16 is limited only to nodes specified in the license agreement. To implement this limitation, there is a PBS resource host_licenses:

-l select=1:ncpus=N: ... :host_licenses=g16

Usage

Batch computation

• prepare the job description script, where you should specify the computation which should be performed over the input file

For example, such a script may look like this one:

#!/bin/bash

#ensure removing the temporary data if the job ends or fails
trap "clean_scratch" TERM EXIT
 
DATADIR="/storage/brno2/home/$LOGNAME"
JOBNAME="myjob"             # myjob.com -> myjob.log

# sanity checks
if [[ -z "$SCRATCHDIR" ]]; then
   echo "use scratch_local, scratch_ssd, or scratch_shared in qsub (resource specification)"
   exit 1
fi

if [[ ! (-f "$DATADIR/${JOBNAME}.com") ]]; then
   echo "the input file '$DATADIR/${JOBNAME}.com' does not exist"
   exit 1
fi

# copy input file from shared network disk to local disk
cp $DATADIR/${JOBNAME}.com $SCRATCHDIR/ || exit 1
cd $SCRATCHDIR/ || exit 2

# let's load the Gaussian module
module add g09

#  myjob.com is the input file
# setup the resource requirements within the input file so that they correspond to the resources reserved
g09-prepare ${JOBNAME}.com

# start the computation (use g16 instead of g09 for the g16 version) , myjob.log will be the output file
g09 ${JOBNAME}.com
# alternatively: g09 < ${JOBNAME}.com > ${JOBNAME}.log

# copy the output from local scratch to shared network disk
cp ${JOBNAME}.log $DATADIR/ || export CLEAN_SCRATCH=false

Pass the startup script to the scheduler together with resource requirements:

qsub -l select=1:ncpus=X:mem=Yg:scratch_local=Zg mydescriptionscript.sh
    

Linda computations (using more machines)

Module g09/D.01linda contains Linda version allowing to use more machines.

If you do not use Linda version, other versions permit computing only on one machine, thus it is nonsense to plan computation on more machines. Although job submission in form

select=Y:ncpus=X

with Y > 1 will not end with an error, it will compute only on one machine like you submit it with select=1:ncpus=X parameter. This results in overcoming the requested resources on memory or scratch size and the job would be killed.

The script remains the same. We only change module add g09 for module add g09/D.01linda and submit the job with a given number of machines N

 qsub -l select=N:ncpus=X:mem=Yg:scratch_local=Zg mydescriptionscript.sh

Interactive computation

Ask for an interactive job having a single node with a specified number of processors (ncpus parameter), a specified amount of memory (mem parameter), and an appropriate amount of scratch space reserved:

qsub -I -l select=1:ncpus=X:mem=Yg:scratch_local=Zg

Load the Gaussian module into the environment:

module add g09

Prepare the Gaussian input file (named, e.g. myinput.com).

g09-prepare myjob.com

Run the computation

g09 myjob.com

(alternatively: g09 <myjob.com >myjob.out)

FAQs

Q: How to tell Gaussian to limit the size of the used /scratch? How to determine, what size had been really used?

A: Once a Gaussian computation finishes, it informs the user about the size of the used files in the following form:

File lengths (MBytes):  RWF=    207 Int=      0 D2E=      0 Chk=    134 Scr=      1

It is possible to limit the amount of the used scratch space using the directives %RWF=,%Int=,%D2E= in the form (if more space is necessary, the computation crashes):

%RWF=/directory/,200GB 

It is also necessary to tell PBS to reserve such a space on the scratch — do it using the -l scratch=XXX parameter (see more information in Scratch storage). The following example ensures an allocation of 200 GB of space on the /scratch volume of the worker node:

-l scratch=200gb 

To set the RWF parameter automatically (based on the resources really reserved for a job), please use the g09-prepare command (see above). When using this script for large computations, one may let the script separate the scratch space into multiple files, which may be automatically erased by Gaussian during the computation (%NoSave).

Note: Alternatively, the amount of scratch space may be limited using the MaxDisk=200GB parameter (however, this is just a hint for some computation methods, which are able to work with a disk using different ways — generally, this parameter does not ensure exceeding of the specified value.)

Q: Memory alocation in program Gaussian version G03.E01 does not work. What should I do?

A: If you get a warning: “buffer allocation failed in ntrext1.” just after running the program, use as work directory $SCRATCHDIR instead of $HOME (there is an error in the new version that occurs according to type of file system)

Q: Which settings are necessary for Linda version?

A: You should specify

%NProcShared=2
%LindaWorkers=doom29,gram7

where the first defines how many cores you need per machine, and the second parameter is the list of machines. g09-prepare sets both parameters by default.