Extracting numerical properties from output files

Quantum packages simulations generate output file in different formats. For examples the SCM simulation suite (ADF and DFTB in QMFlows) generate binary outputs, while other packages like CP2K and ORCA generate ascii text files.

QMFlows abstract away all the different commmunication protocols with the different output formats, allowing the user to extract the desire property by using the convention:

>>> result = job.property

where job is the simulation perform with a given package and property is the numerical value of interest (scalar or array).

The QMFlows implementation of the aforemention mechanism search in the YAML files located at qmflows/data/dictionaries/ for instructions about how to read that given property from the output file. Nevertheless, Not all the properties for a given pacakge are implemented. If the property of your interest is not available you can request it in the Qmflows issues page.


Internally QMFlows uses different mechanism to extract different properties from the output files. In the case of the ADF and DFTB packages, QMFlows take advantages of the python interface to kftools files developed by the SCM. In the case of XML output, QMFlows direcltly uses the python built-in xml reader. For the output files in text format Qmflows uses a mixuture of awk and parsers.

Parsers are a robust alternative to regular expressions, parsers are modular and reusable, while re tends to be abstruse and difficult to reuse. A parser is a function that decomposes a string (or binary) into its syntactic components using some predefined rules or grammar. The library pyparsing offers all the functionality to parse strings, some detail explanation about the library can be found at docs.