In this paper we present computational cost estimates for parallel shared memory isogeometric multi-frontal solver. The estimates show that the ideal isogeometric shared memory parallel direct solver scales as O(p 2 log(N/p)) for one dimensional problems, O(Np 2 ) for two dimensional problems, and O(N 4/3 p 2 ) for three dimensional problems, where N is the number of degrees of freedom, and p is the polynomial order of approximation. The computational costs of the shared memory parallel isogeometric direct solver are compared with those corresponding to the sequential isogeometric direct solver, being the latest equal to O(Np 2 ) for the one dimensional case, O(N 1.5 p 3 ) for the two dimensional case, and O(N 2 p 3 ) for the three dimensional case. The shared memory version significantly reduces both the scalability in terms of N and p. Theoretical estimates are compared with numerical experiments performed with linear, quadratic, cubic, quartic, and quintic B-splines, in one and two spatial dimensions.Keywords: isogeometric finite element method, multi-frontal direct solver, computational cost, NVIDIA CUDA GPU
Preprint submitted to Computers & Mathematics with ApplicationsMarch 27, 20141. Introduction Classical higher order finite element methods (FEM) [17,18] maintain only C 0 -continuity at the element interfaces, while isogeometric analysis (IGA) utilizes B-splines as basis functions, and thus, it delivers C k global continuity [14]. The higher continuity obtained across elements allows IGA to attain optimal convergence rates for any polynomial order, while using fewer degrees of freedom [3,1]. Nevertheless, this reduced count in the number of degrees of freedom may not immediately correlate with a computational cost reduction, since solution time per degree of freedom augments as the continuity is increased [10,13]. In spite of the increased cost of highercontinuous spaces, they have proven very popular and useful. For example, higher-continuous spaces have allowed the solution of higher-order partial di↵erential equations with elegance [7,28,29,51,16,15] as well as several non-linear problems of engineering interest [31,6,30,5,20,11,9,4]. Thus, e cient multi-frontal solvers for higher-continuous spaces are important.The multi-frontal solver is one of the state-of-the art algorithm for solving linear systems of equations [22,26]. It is a generalization of the frontal solver algorithm proposed in [33,21]. The multi-frontal algorithm constructs an assembly tree based on the analysis of the connectivity data or the geometry of the computational mesh. Finite elements are joint into pairs and fully assembled unknowns are eliminated within frontal matrices associated to multiple branches of the tree. The process is repeated until the root of the assembly tree is reached. Finally, the common interface problem is solved and partial backward substitutions are recursively called on the assembly tree.There exist parallel versions of the multi-frontal direct solver algorithm targeting distributed-memory, share...