Environment Detection

QCEngine can inspect the current compute environment to determine the resources available to it.

Node Description

QCEngine can detect node descriptions to obtain general information about the current node.

>>> qcng.config.get_node_descriptor()
<NodeDescriptor hostname_pattern='*' name='default' scratch_directory=None
                memory=5.568 memory_safety_factor=10 ncores=4 jobs_per_node=2>

Config

The configuration file operated based on the current node descriptor and can be overridden:

>>> qcng.get_config()
<JobConfig ncores=2 memory=2.506 scratch_directory=None>

>>> qcng.get_config(local_options={"scratch_directory": "/tmp"})
<JobConfig ncores=2 memory=2.506 scratch_directory='/tmp'>

>>> os.environ["SCRATCH"] = "/my_scratch"
>>> qcng.get_config(local_options={"scratch_directory": "$SCRATCH"})
<JobConfig ncores=2 memory=2.506 scratch_directory='/my_scratch'>

Global Environment

The global environment can also be inspected directly.

>>> qcng.config.get_global()
{
    'hostname': 'qcarchive.molssi.org',
    'memory': 5.568,
    'username': 'user',
    'ncores': 4,
    'cpuinfo': {
        'python_version': '3.6.7.final.0 (64 bit)',
        'brand': 'Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz',
        'hz_advertised': '2.9000 GHz',
        ...
    },
    'cpu_brand': 'Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz'
}

Configuration Files

The computational environment defaults can be overridden by configuration files.

Configuration files must be named qcengine.yaml and stored either in the directory from which you run QCEngine, a folder named .qcarchive in your home directory, or in a folder specified by the DQM_CONFIG_PATH environmental variable. Only one configuration file will be used if multiple are available. The DQM_CONFIG_PATH configuration file takes precedence over the current directory, which takes precedence over the .qcarchive folder.

The configuration file is a YAML file that contains a dictionary of different node configurations. The keys in the YAML file are human-friendly names for the configurations. The values are dictionaries that define configurations for different nodes, following the NodeDescription schema:

class qcengine.config.NodeDescriptor(**data: Dict[str, Any])[source]

Description of an individual node

When running QCEngine, the proper configuration for a node is determined based on the hostname of the node and matching the hostname_pattern to each of the configurations defined in qcengine.yaml.

An example qcengine.yaml file that sets the scratch directory for all nodes is as follows:

Cluster Configuration

A node configuration file is required when using node-parallel tasks on a compute cluster. The configuration file must contain a description of the command used to launch MPI tasks and, in some cases, the designation that a certain node is a compute node. See the descriptions for mpiexec_command and is_batch_node in the NodeDescriptor documentation for further details.