title: Time-dependent density-functional theory in massively parallel computer architectures: the OCTOPUS project.
abstract: Octopus is a general-purpose density-functional theory (DFT) code, with a particular emphasis on the time-dependent version of DFT (TDDFT). In this paper we present the ongoing efforts to achieve the parallelization of octopus. We focus on the real-time variant of TDDFT, where the time-dependent Kohn-Sham equations are directly propagated in time. This approach has great potential for execution in massively parallel systems such as modern supercomputers with thousands of processors and graphics processing units (GPUs). For harvesting the potential of conventional supercomputers, the main strategy is a multi-level parallelization scheme that combines the inherent scalability of real-time TDDFT with a real-space grid domain-partitioning approach. A scalable Poisson solver is critical for the efficiency of this scheme. For GPUs, we show how using blocks of Kohn-Sham states provides the required level of data parallelism and that this strategy is also applicable for code optimization on standard processors. Our results show that real-time TDDFT, as implemented in octopus, can be the method of choice for studying the excited states of large molecular systems in modern parallel architectures.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA. xavier@tddft.org
authors.forename: Xavier
authors.initials: X
authors.lastname: Andrade
authors.forename: Joseba
authors.initials: J
authors.lastname: Alberdi-Rodriguez
authors.forename: David A
authors.initials: DA
authors.lastname: Strubbe
authors.forename: Micael J T
authors.initials: MJ
authors.lastname: Oliveira
authors.forename: Fernando
authors.initials: F
authors.lastname: Nogueira
authors.forename: Alberto
authors.initials: A
authors.lastname: Castro
authors.forename: Javier
authors.initials: J
authors.lastname: Muguerza
authors.forename: Agustin
authors.initials: A
authors.lastname: Arruabarrena
authors.forename: Steven G
authors.initials: SG
authors.lastname: Louie
authors.forename: Alán
authors.initials: A
authors.lastname: Aspuru-Guzik
authors.forename: Angel
authors.initials: A
authors.lastname: Rubio
authors.forename: Miguel A L
authors.initials: MA
authors.lastname: Marques
mesh_terms: D001554:Benzene / Q000737:chemistry; D003196:Computer Graphics; D003201:Computers; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D012984:Software; D013997:Time Factors
chemical_list: D001554:Benzene