X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/GMRES2stage.git/blobdiff_plain/299e2e52d19b38d91f622d1eb8b7af2bb44c7685..6fda575b88fae086f925cd4dcf960fc2af0d3b4f:/paper.tex diff --git a/paper.tex b/paper.tex index 4757973..04ad634 100644 --- a/paper.tex +++ b/paper.tex @@ -626,8 +626,8 @@ inner solver. The current approximation of the Krylov method is then stored insi $S$ composed by the successive solutions that are computed during inner iterations. At each $s$ iterations, the minimization step is applied in order to -compute a new solution $x$. For that, the previous residuals are computed with -$(b-AS)$. The minimization of the residuals is obtained by +compute a new solution $x$. For that, the previous residuals of $Ax=b$ are computed by +the inner iterations with $(b-AS)$. The minimization of the residuals is obtained by \begin{equation} \underset{\alpha\in\mathbb{R}^{s}}{min}\|b-R\alpha\|_2 \label{eq:01} @@ -654,7 +654,7 @@ appropriate than a single direct method in a parallel context. \State $S_{k \mod s}=x^k$ \label{algo:store} \If {$k \mod s=0$ {\bf and} error$>\epsilon_{kryl}$} \State $R=AS$ \Comment{compute dense matrix} \label{algo:matrix_mul} - \State Solve least-square problem $\underset{\alpha\in\mathbb{R}^{s}}{min}\|b-R\alpha\|_2$ \label{algo:} + \State $\alpha=Solve\_Least\_Squares(R,b,max\_iter_{ls})$ \label{algo:} \State $x^k=S\alpha$ \Comment{compute new solution} \EndIf \EndFor @@ -789,7 +789,7 @@ systems obtained with the previous matrices with a GMRES variant and with out 2 stage algorithm are given. In the second column, it can be noticed that either gmres or fgmres is used to solve the linear system. According to the matrices, different preconditioner is used. With TSIRM, the same solver and the same -preconditionner is used. This Table shows that TSIRM can drastically reduce the +preconditionner are used. This Table shows that TSIRM can drastically reduce the number of iterations to reach the convergence when the number of iterations for the normal GMRES is more or less greater than 500. In fact this also depends on tow parameters: the number of iterations to stop GMRES and the number of @@ -823,12 +823,12 @@ torso3 & fgmres / sor & 37.70 & 565 & 34.97 & 510 \\ -In order to perform larger experiments, we have tested some example application +In order to perform larger experiments, we have tested some example applications of PETSc. Those applications are available in the ksp part which is suited for scalable linear equations solvers: \begin{itemize} \item ex15 is an example which solves in parallel an operator using a finite - difference scheme. The diagonal is equals to 4 and 4 extra-diagonals + difference scheme. The diagonal is equal to 4 and 4 extra-diagonals representing the neighbors in each directions is equal to -1. This example is used in many physical phenomena, for example, heat and fluid flow, wave propagation... @@ -940,7 +940,7 @@ the number of iterations. So, the overall benefit of using TSIRM is interesting. \end{table*} -In Table~\ref{tab:04}, some experiments with example ex54 on the Curie architecture are reported +In Table~\ref{tab:04}, some experiments with example ex54 on the Curie architecture are reported. \begin{table*}[htbp] @@ -965,6 +965,13 @@ In Table~\ref{tab:04}, some experiments with example ex54 on the Curie architect \end{center} \end{table*} +\begin{figure}[htbp] +\centering + \includegraphics[width=0.45\textwidth]{nb_iter_sec_ex54_curie} +\caption{Number of iterations per second with ex54 and the same parameters than in Table~\ref{tab:05}} +\label{fig:02} +\end{figure} + %%%********************************************************* %%%*********************************************************