## Section: Software

### PPAT: pseudo-spectrum

Participants : Édouard Canot [ corresponding author ] , Frédéric Guyomarc'h, Bernard Philippe.

PPAT (Parallel PATh following software) is a parallel code, developed by D. Mezher, W. Najem (University of Saint-Joseph, Beirut, Lebanon) and B. Philippe. This tool can follow the
contours of a functional from to .
The present version is adapted for
determining the level curves of the function f(z) = _{min}(A-ZI) which
gives the pseudospectrum of matrix A.

The algorithm is reliable : it does not assume that the curve has a derivative everywhere. The process is proved to terminate even when taking into account roundoff errors. The structure of the code spawns many independent tasks which provide a good efficiency in the parallel runs.

The software can be downloaded under the GPL licence from: http://sourceforge.net/projects/ppat .