Parallelizing the XSTAR Photoionization Code

TL;DR

This paper presents two parallelization methods for the XSTAR photoionization code, significantly improving computational efficiency and enabling more complex astrophysical modeling within practical timeframes.

Contribution

Introduction of pvm_xstar and PModel, enabling parallel execution of XSTAR computations for faster and more complex astrophysical modeling.

Findings

Parallelization increases XSTAR's computational speed.

Enables simultaneous calculation of multiple ionization states.

Expands the feasible problem size for XSTAR applications.

Abstract

We describe two means by which XSTAR, a code which computes physical conditions and emission spectra of photoionized gases, has been parallelized. The first is pvm_xstar, a wrapper which can be used in place of the serial xstar2xspec script to foster concurrent execution of the XSTAR command line application on independent sets of parameters. The second is PModel, a plugin for the Interactive Spectral Interpretation System (ISIS) which allows arbitrary components of a broad range of astrophysical models to be distributed across processors during fitting and confidence limits calculations, by scientists with little training in parallel programming. Plugging the XSTAR family of analytic models into PModel enables multiple ionization states (e.g., of a complex absorber/emitter) to be computed simultaneously, alleviating the often prohibitive expense of the traditional serial approach. Initial performance results indicate that these methods substantially enlarge the problem space to which XSTAR may be applied within practical timeframes.