Balancing Neumann-Neumann methods are extented to mixed formulations of the linear elasticity system with discontinuous coefficients, discretized with mixed finite or spectral elements with discontinuous pressures. These domain decomposition methods implicitly eliminate the degrees of freedom associated with the interior of each subdomain and solve iteratively the resulting saddle point Schur complement using a hybrid preconditioner based on a coarse mixed elasticity problem and local mixed elasticity problems with natural and essential boundary conditions. A polylogarithmic bound in the local number of degrees of freedom is proven for the condition number of the preconditioned operator in the constant coefficient case. Parallel and serial numerical experiments confirm the theoretical results, indicate that they still hold for systems with discontinuous coefficients, and show that our algorithm is scalable, parallel, and robust with respect to material 284 P. Goldfeld et al. heterogeneities. The results on heterogeneous general problems are also supported in part by our theory. Classification (1991): 65N55, 65N30, 65N35, 65F10, 65Y05 Mathematics Subject

No abstract

No abstract

No abstract

With the ultimate goal of designing a scalable parallel preconditioner for reservoir simulation problems, we combine domain decomposition ideas (prove suitable for parallelization) with incomplete factorizations (which are standard in reservoir simulation) at subdomain level. We introduce an ILU(k)-based two-level domain decomposition preconditioner and compare its performance with a two-level ILU(k)-Block-Jacobi preconditioner.