X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/GMRES2stage.git/blobdiff_plain/33840a9b66d39bd2d78f409b7e25a8339280e05a..0f544a712fbfaa8e36e2d89273b1ecf21085669c:/paper.tex diff --git a/paper.tex b/paper.tex index 08e7b8a..3a51e45 100644 --- a/paper.tex +++ b/paper.tex @@ -621,10 +621,11 @@ outer solver periodically applies a least-squares minimization on the residuals At each outer iteration, the sparse linear system $Ax=b$ is partially solved using only $m$ iterations of an iterative method, this latter being initialized with the -best known approximation previously obtained. -GMRES method~\cite{Saad86}, or any of its variants, can be used for instance as an -inner solver. The current approximation of the Krylov method is then stored inside a matrix -$S$ composed by the successive solutions that are computed during inner iterations. +last obtained approximation. +GMRES method~\cite{Saad86}, or any of its variants, can potentially be used as +inner solver. The current approximation of the Krylov method is then stored inside a $n \times s$ matrix +$S$, which is composed by the $s$ last solutions that have been computed during +the inner iterations phase. At each $s$ iterations, the minimization step is applied in order to compute a new solution $x$. For that, the previous residuals of $Ax=b$ are computed by @@ -1029,6 +1030,15 @@ In Table~\ref{tab:04}, some experiments with example ex54 on the Curie architect %%%********************************************************* %%%********************************************************* +A novel two-stage iterative algorithm has been proposed in this article, +in order to accelerate the convergence Krylov iterative methods. +Our TSIRM proposal acts as a merger between Krylov based solvers and +a least-squares minimization step. +The convergence of the method has been proven in some situations, while +experiments up to 16,394 cores have been led to verify that TSIRM runs +5 or 7 times faster than GMRES. + + For future work, the authors' intention is to investigate other kinds of matrices, problems, and inner solvers. The influence of all parameters must be tested too, while