I thank again to José Román for his unique humor sense. To Carmen, for showing me the way and for all her good advices. To Enrique, who helped me to get rolling. And to the former members Andrés and Eloy, to whom I had the opportunity to meet and who enliven the group meals. I will keep good memories from these years. I do not want to forget to mention to Xavier Cartoixà, Jeff Steward and Altuǧ Aksoy, great researchers with whom I have had the opportunity to collaborate. The afternoon snacks would not have been the same without the excellent discussions and comments of Fernando, David and of course Salva, who, without noticing it, also helped to improve this dissertation. Last, I would like to thank to José Luis, IT staff of the department, for his high valuable work behind the scenes and his promptly response to any incidence. To all of you who have supported me, thank you. v de matriz de forma directa. Nosotros hemos implementado varios algoritmos para calcular las funciones de matrices raíz cuadrada y exponencial, en las que el uso de GPUs permite acelerar el cálculo. vi Contents List of Figures xi List of Tables xv List of Algorithms xvii