Restart from a Previous Run

This page explains how to restart a Job from the results of a previous calculation.

1. Understand restart file operations

When a job is added as a parent, some directories and files are copied or linked to the new job working directory. For example, with the Quantum ESPRESSO engine, a link to the parent working directory is created to restart from the last checkpoint. With VASP, the output CONTCAR file generated by the parent job is copied as an input POSCAR structure file to restart from the last ionic step.

2. Example of restart application

This tutorial demonstrates the "restart" functionality by feeding 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 described in a separate tutorial.

Restarting and linking the two Jobs in this way allows the band structure to be computed without recalculating the charge density and wavefunctions through an SCF calculation a second time, reducing computational time. The results of such an SCF Job can be re-utilized as a starting point for multiple other calculations that require such preliminary results.

3. Select the parent job

Within Job Designer, job restarting is accomplished via the Select Parent Option under the main header menu.

First, create a new Job with the NSCF component unit of a band structure calculation present on its own in the main workflow. Follow the same instructions as in the original tutorial to select and insert such a Workflow.

Then, find the previously-run SCF job via the Select Parent option and select that job to prepend its results as a restart precursor to the new NSCF job.

4. Submit the job

The same instructions for submitting and executing the restart Job as in the main band structure tutorial can be followed.

5. Video walkthrough

The animation below demonstrates the steps involved in restarting an NSCF electronic band structure computation, performed on silicon, based upon the preliminary results of a previously-run SCF calculation. The example uses Quantum ESPRESSO, however the same procedure is generally applicable.