ILU-type preconditioning techniques are widely recognized as being an extremely effective approach to providing efficient solvers[1]. These techniques have been used to increase the performance and reliability of Krylov subspace methods. However, a drawback of these approaches is that it is difficult to choose appropriate values for the preconditioner tuning parameters[2]. Usually, parameter se...

we prove that the class of profinite groups $g$ that have a factorization $g=ab$‎ ‎with $a$ and $b$ abelian closed subgroups‎, ‎is closed under taking inverse limits‎ ‎of surjective inverse systems‎. ‎this is a generalization of a recent result by k. h. hofmann and f. g. russo‎. ‎as an application we reprove their generalization of iwasawa's structure theorem for‎ ‎quasihamiltonian pro-$p$...

In many large-scale scientific simulation codes, the majority of computation is devoted to linear solvers. Preconditioned Krylov iterative solver such as conjugate gradient method with incomplete Cholesky factorization preconditioning (ICCG) provides robust convergence for a wide range of scientific applications. Incomplete Cholesky (IC) and incomplete LU (ILU) factorizations involve globally d...

Nowadays reservoir simulators are indispensable tools to reservoir engineers. They are widely used in the optimization and prediction of oil and gas production. However, for large-scale reservoir simulation, computational time is usually too long. A case with over one million grid blocks may run weeks or even months. High performance processors and well-designed software are demanded. Though to...

In this paper we describe an iterative method for indefinite saddle-point systems arising from mixed finite element discretizations of second-order elliptic boundary value problems subject to mixed boundary conditions and posed over polyhedral three-dimensional domains. The method is based on a decoupling of the vector of velocities in the saddle-point system from the vector of pressures, resul...

Linear systems with large differences between the coefficients, called ‘‘discontinuous coefficients’’, often arise when physical phenomena in heterogeneous media are modeled by partial differential equations (PDEs). Such problems are usually solved by domain decomposition techniques, but these can be difficult to implement when subdomain boundaries are complicated or the grid is unstructured. I...

This paper prescnts tlic cxpericnce of using the Common Object Requcst Broker Architecture (CORBA)[ I] in tlic ATLAS prototype DAQ project[2]. Many coiiiniunication links in the DAQ systcm have been dcsigned and implcmentcd using thc CORBA standard. A public domain package, callcd Inter-Language Unification (ILU)[3] has bccn used to implement C O R M based communications between DAQ componcnts ...

in this paper‎, ‎we determine the simple groups $g=ab$‎, ‎where $b$ is isomorphic to $l_{3}(4)$ and $a$ isomorphic to an alternating or a symmetric group on $ngeq5$‎, ‎letters‎.