ORCA¶

Background¶

Prerequisites

Have followed the Spack introductions.

ORCA is a general-purpose quantum chemistry program. After registration on the ORCA website, it is provided as pre-built software for various system configurations. One dependency which needs to be matched is the version of OpenMPI used for the version of ORCA and the architecture (e.g. Arm).

Build¶

To use ORCA copy the downloaded installation file (e.g. orca_6_0_1_linux_arm64_shared_openmpi418.tar.xz) to your home directory. Following instructions for Spack there is an example build script in the "buildit" repository within apps/orca/3 for Isambard 3.

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# Change to directory with example build script.
cd buildit/apps/orca/3
# Move the installation file to build directory
mv $HOME/orca_6_0_1_linux_arm64_shared_openmpi418.tar.xz .
# Run the build script.
./build.sh

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Run¶

To run ORCA the following job script can be used.

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#!/bin/bash

#SBATCH --nodes=1
#SBATCH --ntasks-per-node=28
#SBATCH --cpus-per-task=1
#SBATCH --time=1-00:00:0
#SBATCH --mem=0
#SBATCH --output=output.txt
#SBATCH --exclusive

# This assumes running inside the same directory installed
# myenv, spack and buildit directory should be found here.

# Load the Spack environment
. spack/share/spack/setup-env.sh

# Activate environment
spack env activate myenv

# PMIX is required for OpenMPI
export SLURM_MPI_TYPE=pmix

# This allows libfabric to setup single node MPI
export SLURM_NETWORK=single_node_vni

# Due to a bug the default bcast algorithm doesnt work
export OMPI_MCA_coll_tuned_use_dynamic_rules=1
export OMPI_MCA_coll_tuned_bcast_algorithm=1

# ORCA is called directly and expected to be full path.
ORCA_EXE=`which orca`

# Run with input file input.inp
$ORCA_EXE input.inp

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Further help¶

Refer to support page for available options.