X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/book_gpu.git/blobdiff_plain/17bff40b83bcdcc39769f9e59c70ffae1c525b72..55ce7168c6e69a2462d76c95dc9a5298ceedb04f:/BookGPU/Chapters/chapter12/ch12.tex?ds=sidebyside diff --git a/BookGPU/Chapters/chapter12/ch12.tex b/BookGPU/Chapters/chapter12/ch12.tex index 0269fd2..4bc95a6 100755 --- a/BookGPU/Chapters/chapter12/ch12.tex +++ b/BookGPU/Chapters/chapter12/ch12.tex @@ -19,7 +19,7 @@ \label{ch12:sec:01} Sparse linear systems are used to model many scientific and industrial problems, such as the environmental simulations or the industrial processing of the complex or -non-Newtonian fluids. Moreover, the resolution of these problems often involves the +nonNewtonian fluids. Moreover, the resolution of these problems often involves the solving of such linear systems that are considered the most expensive process in terms of execution time and memory space. Therefore, solving sparse linear systems must be as efficient as possible in order to deal with problems of ever increasing @@ -457,8 +457,8 @@ nodes\index{neighboring node} over the GPU cluster must exchange between them th elements necessary to compute this multiplication. First, each computing node determines, in its local subvector, the vector elements needed by other nodes. Then, the neighboring nodes exchange between them these shared vector elements. The data exchanges are implemented by using the MPI -point-to-point communication routines: blocking\index{MPI subroutines!blocking} sends with \verb+MPI_Send()+ -and nonblocking\index{MPI subroutines!nonblocking} receives with \verb+MPI_Irecv()+. Figure~\ref{ch12:fig:02} +point-to-point communication routines: blocking\index{MPI!blocking} sends with \verb+MPI_Send()+ +and nonblocking\index{MPI!nonblocking} receives with \verb+MPI_Irecv()+. Figure~\ref{ch12:fig:02} shows an example of data exchanges between \textit{Node 1} and its neighbors \textit{Node 0}, \textit{Node 2}, and \textit{Node 3}. In this example, the iterate matrix $A$ split between these four computing nodes is that presented in Figure~\ref{ch12:fig:01}. @@ -491,7 +491,7 @@ cluster. Consequently, the vector elements to be exchanged must be copied from t and vice versa before and after the synchronization operation between CPUs. We have used the CUBLAS\index{CUBLAS} communication subroutines to perform the data transfers between a CPU core and its GPU: \verb+cublasGetVector()+ and \verb+cublasSetVector()+. Finally, in addition to the data exchanges, GPU nodes perform reduction operations -to compute in parallel the dot products and Euclidean norms. This is implemented by using the MPI global communication\index{MPI subroutines!global} +to compute in parallel the dot products and Euclidean norms. This is implemented by using the MPI global communication\index{MPI!global} \verb+MPI_Allreduce()+. @@ -548,8 +548,10 @@ which are the number of rows, the total number of nonzero values, and the maxima the present chapter, the bandwidth of a sparse matrix is defined as the number of matrix columns separating the first and the last nonzero value on a matrix row. + \begin{table} \centering +\begin{small} \begin{tabular}{|c|c|c|c|c|} \hline {\bf Matrix Type} & {\bf Matrix Name} & {\bf \# Rows} & {\bf \# Nonzeros} & {\bf Bandwidth} \\ \hline \hline @@ -578,10 +580,12 @@ the first and the last nonzero value on a matrix row. & torso3 & $259,156$ & $4,429,042$ & $216,854$ \\ \hline \end{tabular} +\end{small} \caption{Main characteristics of sparse matrices chosen from the University of Florida collection.} \label{ch12:tab:01} \end{table} + \begin{table}[!h] \begin{center} \begin{tabular}{|c|c|c|c|c|c|c|} @@ -607,6 +611,7 @@ thermal2 & $1.172s$ & $0.622s$ & $1.88$ & $ \begin{table}[!h] \begin{center} +\begin{small} \begin{tabular}{|c|c|c|c|c|c|c|} \hline {\bf Matrix} & $\mathbf{Time_{cpu}}$ & $\mathbf{Time_{gpu}}$ & $\mathbf{\tau}$ & $\mathbf{\#~Iter.}$ & $\mathbf{Prec.}$ & $\mathbf{\Delta}$ \\ \hline \hline @@ -635,6 +640,7 @@ poli\_large & $0.097s$ & $0.095s$ & $1.02$ & $ torso3 & $4.242s$ & $2.030s$ & $2.09$ & $175$ & $2.69e$-$10$ & $1.78e$-$14$ \\ \hline \end{tabular} +\end{small} \caption{Performances of the parallel GMRES method on a cluster 24 CPU cores vs. on cluster of 12 GPUs.} \label{ch12:tab:03} \end{center} @@ -742,7 +748,7 @@ are better than those of the GMRES method for solving large symmetric linear sys CG method is characterized by a better convergence\index{convergence} rate and a shorter execution time of an iteration than those of the GMRES method. Moreover, an iteration of the parallel GMRES method requires more data exchanges between computing nodes compared to the parallel CG method. - +\clearpage \begin{table}[!h] \begin{center} \begin{tabular}{|c|c|c|c|c|c|c|} @@ -769,6 +775,7 @@ on a cluster of 12 GPUs.} \begin{table}[!h] \begin{center} +\begin{small} \begin{tabular}{|c|c|c|c|c|c|c|} \hline {\bf Matrix} & $\mathbf{Time_{cpu}}$ & $\mathbf{Time_{gpu}}$ & $\mathbf{\tau}$ & $\mathbf{\#~Iter.}$ & $\mathbf{Prec.}$ & $\mathbf{\Delta}$ \\ \hline \hline @@ -797,6 +804,7 @@ poli\_large & $8.515s$ & $1.053s$ & $8.09$ torso3 & $31.463s$ & $3.681s$ & $8.55$ & $175$ & $2.69e$-$10$ & $2.66e$-$14$ \\ \hline \end{tabular} +\end{small} \caption{Performances of the parallel GMRES method for solving linear systems associated to sparse banded matrices on a cluster of 24 CPU cores vs. on a cluster of 12 GPUs.} \label{ch12:tab:06}