TITLE: On the computation of reducible invariant tori in a parallel computer AUTHORS: Angel Jorba and Estrella Olmedo Departament de Matematica Aplicada i Analisi. Universitat de Barcelona. Gran Via 585, 08007, Barcelona, Spain. E-mails: angel@maia.ub.es, estrella@maia.ub.es ABSTRACT: We present an algorithm for the computation of reducible quasi-periodic solutions of discrete dynamical systems. The method is based on a quadratically convergent scheme that approximates, at the same time, the Fourier series of the torus, its Floquet transformation and its Floquet matrix. The Floquet matrix describes the linearization of the dynamics around the torus and, hence, its linear stability. The algorithm presents a high degree of parallelism and the computational effort grows linearly with the number of Fourier modes needed to represent the solution. For these reasons it is a very good option to compute quasi-periodic solutions with several basic frequencies. The paper includes some examples to show the efficiency of the method in a parallel computer.