X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/GMRES2stage.git/blobdiff_plain/bc1dce00ad69fb9121094a9f084dee3a9457d815..23054d081ea510f87cf5c9d8ed9351034ffa8f45:/paper.tex diff --git a/paper.tex b/paper.tex index 7e4945e..c183ea4 100644 --- a/paper.tex +++ b/paper.tex @@ -601,15 +601,15 @@ is summarized while intended perspectives are provided. %%%********************************************************* \section{Related works} \label{sec:02} -Krylov subspace iteration methods have increasingly become useful and successful -techniques for solving linear, nonlinear systems and eigenvalue problems, -especially since the increase development of the +Krylov subspace iteration methods have increasingly become key +techniques for solving linear and nonlinear systems, or eigenvalue problems, +especially since the increasing development of preconditioners~\cite{Saad2003,Meijerink77}. One reason of the popularity of -these methods is their generality, simplicity and efficiency to solve systems of +these methods is their generality, simplicity, and efficiency to solve systems of equations arising from very large and complex problems. GMRES is one of the most widely used Krylov iterative method for solving sparse -and large linear systems. It is developed by Saad and al.~\cite{Saad86} as a +and large linear systems. It has been developed by Saad \emph{et al.}~\cite{Saad86} as a generalized method to deal with unsymmetric and non-Hermitian problems, and indefinite symmetric problems too. In its original version called full GMRES, it minimizes the residual over the current Krylov subspace until convergence in at @@ -1138,12 +1138,12 @@ Concerning the experiments some other remarks are interesting. examples, we also obtained similar gain between GMRES and TSIRM but those examples are not scalable with many cores. In general, we had some problems with more than $4,096$ cores. -\item We have tested many iterative solvers available in PETSc. In fast, it is +\item We have tested many iterative solvers available in PETSc. In fact, it is possible to use most of them with TSIRM. From our point of view, the condition to use a solver inside TSIRM is that the solver must have a restart - feature. More precisely, the solver must support to be stoped and restarted + feature. More precisely, the solver must support to be stopped and restarted without decrease its converge. That is why with GMRES we stop it when it is - naturraly restarted (i.e. with $m$ the restart parameter). The Conjugate + naturally restarted (i.e. with $m$ the restart parameter). The Conjugate Gradient (CG) and all its variants do not have ``restarted'' version in PETSc, so they are not efficient. They will converge with TSIRM but not quickly because if we compare a normal CG with a CG for which we stop it each 16