X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/book_gpu.git/blobdiff_plain/1874c46934f4ba7e8c2013d3829f65309456d292..17bff40b83bcdcc39769f9e59c70ffae1c525b72:/BookGPU/Chapters/chapter12/ch12.tex?ds=inline diff --git a/BookGPU/Chapters/chapter12/ch12.tex b/BookGPU/Chapters/chapter12/ch12.tex index a514438..0269fd2 100755 --- a/BookGPU/Chapters/chapter12/ch12.tex +++ b/BookGPU/Chapters/chapter12/ch12.tex @@ -217,7 +217,7 @@ r_k \bot A \mathcal{K}_k(A, v_1). \end{array} \label{ch12:eq:13} \end{equation} -GMRES uses the Arnoldi process~\cite{ch12:ref5}\index{iterative method!Arnoldi process} to construct an +GMRES uses the Arnoldi iterations~\cite{ch12:ref5}\index{iterative method!Arnoldi iterations} to construct an orthonormal basis $V_k$ for the Krylov subspace $\mathcal{K}_k$ and an upper Hessenberg matrix\index{Hessenberg matrix} $\bar{H}_k$ of order $(k+1)\times k$: \begin{equation} @@ -313,7 +313,7 @@ $V$ to $m$ orthogonal vectors. Algorithm~\ref{ch12:alg:02} shows the key points of the GMRES method with restarts. It solves the left-preconditioned\index{sparse linear system!preconditioned} sparse linear system~(\ref{ch12:eq:11}), such that $M$ is the preconditioning matrix. At each iteration -$k$, GMRES uses the Arnoldi process\index{iterative method!Arnoldi process} (defined from +$k$, GMRES uses the Arnoldi iterations\index{iterative method!Arnoldi iterations} (defined from line~$7$ to line~$17$) to construct a basis $V_m$ of $m$ orthogonal vectors and an upper Hessenberg matrix\index{Hessenberg matrix} $\bar{H}_m$ of size $(m+1)\times m$. Then, it solves the linear least-squares problem of size $m$ to find the vector $y\in\mathbb{R}^{m}$ @@ -526,7 +526,7 @@ is managed by one MPI process and is composed of one CPU core and one GPU card. All tests are made on double-precision floating point operations. The parameters of both linear solvers are initialized as follows: the residual tolerance threshold $\varepsilon=10^{-12}$, the maximum number of iterations $maxiter=500$, the right-hand side $b$ is filled with $1.0$, and the -initial guess $x_0$ is filled with $0.0$. In addition, we limited the Arnoldi process\index{iterative method!Arnoldi process} +initial guess $x_0$ is filled with $0.0$. In addition, we limited the Arnoldi iterations\index{iterative method!Arnoldi iterations} used in the GMRES method to $16$ iterations ($m=16$). For the sake of simplicity, we have chosen the preconditioner $M$ as the main diagonal of the sparse matrix $A$. Indeed, it allows us to easily compute the required inverse matrix $M^{-1}$, and it provides a relatively good preconditioning for