Restart From Previous Run¶
This page explains how to restart a Job from the results of a previous calculation.
Restart File Operations¶
When a job is added as a parent in this way, some directories and files are copied/linked to the new job working directory. For example, for the case of the Quantum ESPRESSO modeling engine, we create a link to the parent working directory to restart the calculation from the last checkpoint. Alternatively, for the case of VASP, we copy the output CONTCAR file generated by the parent job as an input POSCAR structure file to restart from the last ionic step.
Example of Restart Application¶
In the present tutorial we will, by way of an example, make use of the "restart" functionality to feed the wavefunction data obtained in a self-consistent field (SCF) Total Energy computation to the subsequent non-self consistent (NSCF) step in an electronic band structure calculation, which is reviewed in a separate tutorial.
Restarting and linking the two Jobs in this way allows the band structure to be computed without having to recalculate the charge density and wavefunctions through an SCF calculation a second time, with the consequent gain in computational time. The results of such SCF Job can thus be re-utilized as starting point for multiple other calculations that require such preliminary results.
Select Parent Job¶
The user should first create a new Job, with the NSCF component unit of a band structure calculation present on its own in the main workflow. The same instructions as in the original tutorial should be followed to select and insert such a Workflow into the new Job being designed.
The next steps consist in finding the previously-run SCF job via the aforementioned "Select Parent" option, and in selecting that job in order to prepend its results as a restart precursor to the new NSCF job being created.
The same instructions for submitting and executing the restart Job as in the main band structure tutorial can be followed.
In the following animation, we demonstrate the above-mentioned steps involved in restarting an NSCF electronic band structure computation, performed on silicon, based upon the preliminary results of a previously-run SCF calculation. We shall make use of the Quantum ESPRESSO simulation engine in the present example, however the same procedure and outcome should be of general applicability.