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 .