X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/hpcc2014.git/blobdiff_plain/8af7de742ea7a8327a7d2fb131d94fca23d31c28..70f82cf5e87fbbebce020a9163579a602385a7ff:/hpcc.tex diff --git a/hpcc.tex b/hpcc.tex index c457958..a5f2768 100644 --- a/hpcc.tex +++ b/hpcc.tex @@ -1,439 +1,273 @@ - -%% bare_conf.tex -%% V1.3 -%% 2007/01/11 -%% by Michael Shell -%% See: -%% http://www.michaelshell.org/ -%% for current contact information. -%% -%% This is a skeleton file demonstrating the use of IEEEtran.cls -%% (requires IEEEtran.cls version 1.7 or later) with an IEEE conference paper. -%% -%% Support sites: -%% http://www.michaelshell.org/tex/ieeetran/ -%% http://www.ctan.org/tex-archive/macros/latex/contrib/IEEEtran/ -%% and -%% http://www.ieee.org/ - -%%************************************************************************* -%% Legal Notice: -%% This code is offered as-is without any warranty either expressed or -%% implied; without even the implied warranty of MERCHANTABILITY or -%% FITNESS FOR A PARTICULAR PURPOSE! -%% User assumes all risk. -%% In no event shall IEEE or any contributor to this code be liable for -%% any damages or losses, including, but not limited to, incidental, -%% consequential, or any other damages, resulting from the use or misuse -%% of any information contained here. -%% -%% All comments are the opinions of their respective authors and are not -%% necessarily endorsed by the IEEE. -%% -%% This work is distributed under the LaTeX Project Public License (LPPL) -%% ( http://www.latex-project.org/ ) version 1.3, and may be freely used, -%% distributed and modified. 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Do not be tempted to use the -% cuted.sty or midfloat.sty packages (also by Sigitas Tolusis) as IEEE does -% not format its papers in such ways. +\algnewcommand\algorithmicinput{\textbf{Input:}} +\algnewcommand\Input{\item[\algorithmicinput]} +\algnewcommand\algorithmicoutput{\textbf{Output:}} +\algnewcommand\Output{\item[\algorithmicoutput]} +\newcommand{\MI}{\mathit{MaxIter}} +\begin{document} -% *** PDF, URL AND HYPERLINK PACKAGES *** -% -%\usepackage{url} -% url.sty was written by Donald Arseneau. It provides better support for -% handling and breaking URLs. url.sty is already installed on most LaTeX -% systems. The latest version can be obtained at: -% http://www.ctan.org/tex-archive/macros/latex/contrib/misc/ -% Read the url.sty source comments for usage information. Basically, -% \url{my_url_here}. +\title{Simulation of Asynchronous Iterative Numerical Algorithms Using SimGrid} -% *** Do not adjust lengths that control margins, column widths, etc. *** -% *** Do not use packages that alter fonts (such as pslatex). *** -% There should be no need to do such things with IEEEtran.cls V1.6 and later. -% (Unless specifically asked to do so by the journal or conference you plan -% to submit to, of course. ) +\author{% + \IEEEauthorblockN{% + Charles Emile Ramamonjisoa\IEEEauthorrefmark{1}, + David Laiymani\IEEEauthorrefmark{1}, + Arnaud Giersch\IEEEauthorrefmark{1}, + Lilia Ziane Khodja\IEEEauthorrefmark{2} and + Raphaël Couturier\IEEEauthorrefmark{1} + } + \IEEEauthorblockA{\IEEEauthorrefmark{1}% + Femto-ST Institute -- DISC Department\\ + Université de Franche-Comté, + IUT de Belfort-Montbéliard\\ + 19 avenue du Maréchal Juin, BP 527, 90016 Belfort cedex, France\\ + Email: \email{{charles.ramamonjisoa,david.laiymani,arnaud.giersch,raphael.couturier}@univ-fcomte.fr} + } + \IEEEauthorblockA{\IEEEauthorrefmark{2}% + Inria Bordeaux Sud-Ouest\\ + 200 avenue de la Vieille Tour, 33405 Talence cedex, France \\ + Email: \email{lilia.ziane@inria.fr} + } +} +\maketitle +\RC{Ordre des autheurs pas définitif.} +\begin{abstract} +ABSTRACT + +In recent years, the scalability of large-scale implementation in a +distributed environment of algorithms becoming more and more complex has +always been hampered by the limits of physical computing resources +capacity. One solution is to run the program in a virtual environment +simulating a real interconnected computers architecture. The results are +convincing and useful solutions are obtained with far fewer resources +than in a real platform. However, challenges remain for the convergence +and efficiency of a class of algorithms that concern us here, namely +numerical parallel iterative algorithms executed in asynchronous mode, +especially in a large scale level. Actually, such algorithm requires a +balance and a compromise between computation and communication time +during the execution. Two important factors determine the success of the +experimentation: the convergence of the iterative algorithm on a large +scale and the execution time reduction in asynchronous mode. Once again, +from the current work, a simulated environment like Simgrid provides +accurate results which are difficult or even impossible to obtain in a +physical platform by exploiting the flexibility of the simulator on the +computing units clusters and the network structure design. Our +experimental outputs showed a saving of up to 40 \% for the algorithm +execution time in asynchronous mode compared to the synchronous one with +a residual precision up to E-11. Such successful results open +perspectives on experimentations for running the algorithm on a +simulated large scale growing environment and with larger problem size. + +Keywords : Algorithm distributed iterative asynchronous simulation +simgrid -\usepackage[T1]{fontenc} -\usepackage{ucs} -%\usepackage[utf8x]{inputenc} -\usepackage{lmodern} -\usepackage{color} -%% Jolis entetes %% -\usepackage[Glenn]{fncychap} -%\usepackage{amsmath} -%\usepackage{amsthm} -%\usepackage{amsfonts} -%\usepackage{graphicx} -%\usepackage{xspace} -% Definition des marges -\usepackage{vmargin} -\setpapersize[portrait]{A4} -\usepackage[francais]{babel} -% Extension pour les graphiques EPS -%\usepackage[dvips]{graphicx} -\usepackage[pdftex,final]{graphicx} -% Extension pour les liens intra-documents (tagged PDF) -% et l'affichage correct des URL (commande \url{http://example.com}) -\usepackage{hyperref} +\end{abstract} -\ifCLASSINFOpdf - \usepackage[pdftex]{graphicx} - \DeclareGraphicsExtensions{.pdf,.jpeg,.png} -\else -\fi +\section{Introduction} +Parallel computing and high performance computing (HPC) are becoming +more and more imperative for solving various problems raised by +researchers on various scientific disciplines but also by industrial in +the field. Indeed, the increasing complexity of these requested +applications combined with a continuous increase of their sizes lead to +write distributed and parallel algorithms requiring significant hardware +resources (grid computing, clusters, broadband network, etc\dots{}) but +also a non-negligible CPU execution time. We consider in this paper a +class of highly efficient parallel algorithms called iterative executed +in a distributed environment. As their name suggests, these algorithm +solves a given problem that might be NP- complete complex by successive +iterations ($X_{n +1} = f(X_{n})$) from an initial value $X_{0}$ to find +an approximate value $X^*$ of the solution with a very low +residual error. Several well-known methods demonstrate the convergence +of these algorithms. Generally, to reduce the complexity and the +execution time, the problem is divided into several \emph{pieces} that will +be solved in parallel on multiple processing units. The latter will +communicate each intermediate results before a new iteration starts +until the approximate solution is reached. These distributed parallel +computations can be performed either in \emph{synchronous} communication mode +where a new iteration begin only when all nodes communications are +completed, either \emph{asynchronous} mode where processors can continue +independently without or few synchronization points. Despite the +effectiveness of iterative approach, a major drawback of the method is +the requirement of huge resources in terms of computing capacity, +storage and high speed communication network. Indeed, limited physical +resources are blocking factors for large-scale deployment of parallel +algorithms. + +In recent years, the use of a simulation environment to execute parallel +iterative algorithms found some interests in reducing the highly cost of +access to computing resources: (1) for the applications development life +cycle and in code debugging (2) and in production to get results in a +reasonable execution time with a simulated infrastructure not accessible +with physical resources. Indeed, the launch of distributed iterative +asynchronous algorithms to solve a given problem on a large-scale +simulated environment challenges to find optimal configurations giving +the best results with a lowest residual error and in the best of +execution time. According our knowledge, no testing of large-scale +simulation of the class of algorithm solving to achieve real results has +been undertaken to date. We had in the scope of this work implemented a +program for solving large non-symmetric linear system of equations by +numerical method GMRES (Generalized Minimal Residual) in the simulation +environment SimGrid. The simulated platform had allowed us to launch +the application from a modest computing infrastructure by simulating +different distributed architectures composed by clusters nodes +interconnected by variable speed networks. In addition, it has been +permitted to show the effectiveness of asynchronous mode algorithm by +comparing its performance with the synchronous mode time. With selected +parameters on the network platforms (bandwidth, latency of inter cluster +network) and on the clusters architecture (number, capacity calculation +power) in the simulated environment, the experimental results have +demonstrated not only the algorithm convergence within a reasonable time +compared with the physical environment performance, but also a time +saving of up to \np[\%]{40} in asynchronous mode. + +This article is structured as follows: after this introduction, the next +section will give a brief description of iterative asynchronous model. +Then, the simulation framework SimGrid will be presented with the +settings to create various distributed architectures. The algorithm of +the multi -splitting method used by GMRES written with MPI primitives +and its adaptation to SimGrid with SMPI (Simulated MPI) will be in the +next section. At last, the experiments results carried out will be +presented before the conclusion which we will announce the opening of +our future work after the results. + +\section{The asynchronous iteration model} +Décrire le modèle asynchrone. Je m'en charge (DL) -% correct bad hyphenation here -\hyphenation{op-tical net-works semi-conduc-tor} +\section{SimGrid} +Décrire SimGrid~\cite{casanova+legrand+quinson.2008.simgrid} (Arnaud) -\begin{document} -% -% paper title -% can use linebreaks \\ within to get better formatting as desired -\title{Simulation of Asynchronous Iterative Numerical Algorithms Using SimGrid} -% author names and affiliations -% use a multiple column layout for up to three different -% affiliations -\author{\IEEEauthorblockN{Raphaël Couturier and Arnaud Giersch and David Laiymani and Charles-Emile Ramamonjisoa} -\IEEEauthorblockA{Femto-ST Institute - DISC Department\\ -Université de Franche-Comté\\ -Belfort\\ -Email: raphael.couturier@univ-fcomte.fr} -%\and -%\IEEEauthorblockN{Arnaud Giersch} -%\IEEEauthorblockA{Twentieth Century Fox\\ -%Springfield, USA\\ -%Email: homer@thesimpsons.com} -%\and -%\IEEEauthorblockN{James Kirk\\ and Montgomery Scott} -%\IEEEauthorblockA{Starfleet Academy\\ -%San Francisco, California 96678-2391\\ -%Telephone: (800) 555--1212\\ -%Fax: (888) 555--1212 -} -% make the title area -\maketitle +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\section{Simulation of the multisplitting method} +%Décrire le problème (algo) traité ainsi que le processus d'adaptation à SimGrid. +Let $Ax=b$ be a large sparse system of $n$ linear equations in $\mathbb{R}$, where $A$ is a sparse square and nonsingular matrix, $x$ is the solution vector and $b$ is the right-hand side vector. We use a multisplitting method based on the block Jacobi splitting to solve this linear system on a large scale platform composed of $L$ clusters of processors. In this case, we apply a row-by-row splitting without overlapping +\[ +\left(\begin{array}{ccc} +A_{11} & \cdots & A_{1L} \\ +\vdots & \ddots & \vdots\\ +A_{L1} & \cdots & A_{LL} +\end{array} \right) +\times +\left(\begin{array}{c} +X_1 \\ +\vdots\\ +X_L +\end{array} \right) += +\left(\begin{array}{c} +B_1 \\ +\vdots\\ +B_L +\end{array} \right)\] +in such a way that successive rows of matrix $A$ and both vectors $x$ and $b$ are assigned to one cluster, where for all $l,m\in\{1,\ldots,L\}$ $A_{lm}$ is a rectangular block of $A$ of size $n_l\times n_m$, $X_l$ and $B_l$ are sub-vectors of $x$ and $b$, respectively, of size $n_l$ each and $\sum_{l} n_l=\sum_{m} n_m=n$. -\begin{abstract} -%\boldmath -The abstract goes here. -\end{abstract} -% IEEEtran.cls defaults to using nonbold math in the Abstract. -% This preserves the distinction between vectors and scalars. However, -% if the conference you are submitting to favors bold math in the abstract, -% then you can use LaTeX's standard command \boldmath at the very start -% of the abstract to achieve this. Many IEEE journals/conferences frown on -% math in the abstract anyway. +The multisplitting method proceeds by iteration to solve in parallel the linear system on $L$ clusters of processors, in such a way each sub-system +\begin{equation} +\left\{ +\begin{array}{l} +A_{ll}X_l = Y_l \mbox{,~such that}\\ +Y_l = B_l - \displaystyle\sum_{\substack{m=1\\ m\neq l}}^{L}A_{lm}X_m +\end{array} +\right. +\label{eq:4.1} +\end{equation} +is solved independently by a cluster and communications are required to update the right-hand side sub-vector $Y_l$, such that the sub-vectors $X_m$ represent the data dependencies between the clusters. As each sub-system (\ref{eq:4.1}) is solved in parallel by a cluster of processors, our multisplitting method uses an iterative method as an inner solver which is easier to parallelize and more scalable than a direct method. In this work, we use the parallel algorithm of GMRES method~\cite{ref1} which is one of the most used iterative method by many researchers. -% no keywords +\begin{algorithm} +\caption{A multisplitting solver with GMRES method} +\begin{algorithmic}[1] +\Input $A_l$ (sparse sub-matrix), $B_l$ (right-hand side sub-vector) +\Output $X_l$ (solution sub-vector)\vspace{0.2cm} +\State Load $A_l$, $B_l$ +\State Set the initial guess $x^0$ +\For {$k=0,1,2,\ldots$ until the global convergence} +\State Restart outer iteration with $x^0=x^k$ +\State Inner iteration: \Call{InnerSolver}{$x^0$, $k+1$} +\State Send shared elements of $X_l^{k+1}$ to neighboring clusters +\State Receive shared elements in $\{X_m^{k+1}\}_{m\neq l}$ +\EndFor +\Statex +\Function {InnerSolver}{$x^0$, $k$} +\State Compute local right-hand side $Y_l$: \[Y_l = B_l - \sum\nolimits^L_{\substack{m=1 \\m\neq l}}A_{lm}X_m^0\] +\State Solving sub-system $A_{ll}X_l^k=Y_l$ with the parallel GMRES method +\State \Return $X_l^k$ +\EndFunction +\end{algorithmic} +\label{algo:01} +\end{algorithm} +Algorithm~\ref{algo:01} shows the main key points of the multisplitting method to solve a large sparse linear system. This algorithm is based on an outer-inner iteration method where the parallel synchronous GMRES method is used to solve the inner iteration. It is executed in parallel by each cluster of processors. For all $l,m\in\{1,\ldots,L\}$, the matrices and vectors with the subscript $l$ represent the local data for cluster $l$, while $\{A_{lm}\}_{m\neq l}$ are off-diagonal matrices of sparse matrix $A$ and $\{X_m\}_{m\neq l}$ contain vector elements of solution $x$ shared with neighboring clusters. At every outer iteration $k$, asynchronous communications are performed between processors of the local cluster and those of distant clusters (lines $6$ and $7$ in Algorithm~\ref{algo:01}). The shared vector elements of the solution $x$ are exchanged by message passing using MPI non-blocking communication routines. -% For peer review papers, you can put extra information on the cover -% page as needed: -% \ifCLASSOPTIONpeerreview -% \begin{center} \bfseries EDICS Category: 3-BBND \end{center} -% \fi -% -% For peerreview papers, this IEEEtran command inserts a page break and -% creates the second title. It will be ignored for other modes. -\IEEEpeerreviewmaketitle +\begin{figure} +\centering + \includegraphics[width=60mm,keepaspectratio]{clustering} +\caption{Example of three clusters of processors interconnected by a virtual unidirectional ring network.} +\label{fig:4.1} +\end{figure} +The global convergence of the asynchronous multisplitting solver is detected when the clusters of processors have all converged locally. We implemented the global convergence detection process as follows. On each cluster a master processor is designated (for example the processor with rank $1$) and masters of all clusters are interconnected by a virtual unidirectional ring network (see Figure~\ref{fig:4.1}). During the resolution, a Boolean token circulates around the virtual ring from a master processor to another until the global convergence is achieved. So starting from the cluster with rank $1$, each master processor $i$ sets the token to {\it True} if the local convergence is achieved or to {\it False} otherwise, and sends it to master processor $i+1$. Finally, the global convergence is detected when the master of cluster $1$ receives from the master of cluster $L$ a token set to {\it True}. In this case, the master of cluster $1$ broadcasts a stop message to masters of other clusters. In this work, the local convergence on each cluster $l$ is detected when the following condition is satisfied +\[(k\leq \MI) \mbox{~or~} (\|X_l^k - X_l^{k+1}\|_{\infty}\leq\epsilon)\] +where $\MI$ is the maximum number of outer iterations and $\epsilon$ is the tolerance threshold of the error computed between two successive local solution $X_l^k$ and $X_l^{k+1}$. +\LZK{Description du processus d'adaptation de l'algo multisplitting à SimGrid} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -\section{Introduction} -Présenter un bref état de l'art sur la simulation d'algos parallèles. Présenter rapidement les algos itératifs asynchrones et leurs avantages. Parler de leurs inconvénients en particulier la difficulté de déploiement à grande échelle donc il serait bien de simuler. Dire qu'à notre connaissance il n'existe pas de simulation de ce type d'algo. -Présenter les travaux et les résultats obtenus. Annoncer le plan. - -\section{The asynchronous iteration model} -Décrire le modèle asynchrone. Je m'en charge (DL) -\section{SimGrid} -Décrire SimGrid (Arnaud) -\section{Simulation of the multi-splitting method} -Décrire le problème (algo) traité ainsi que le processus d'adaptation à SimGrid. \section{Experimental results} -{\raggedright + When the ``real'' application runs in the simulation environment and produces the expected results, varying the input parameters and the program arguments allows us to compare outputs from the code execution. We have noticed from this @@ -447,263 +281,161 @@ algorithm but also to get the main objective of the experimentation of the simulation in having an execution time in asynchronous less than in synchronous mode, in others words, in having a ``speedup'' less than 1 (Speedup = Execution time in synchronous mode / Execution time in asynchronous mode). -} -{\raggedright A priori, obtaining a speedup less than 1 would be difficult in a local area network configuration where the synchronous mode will take advantage on the rapid exchange of information on such high-speed links. Thus, the methodology adopted was to launch the application on clustered network. In this last configuration, -degrading the inter-cluster network performance will "penalize" the synchronous +degrading the inter-cluster network performance will \emph{penalize} the synchronous mode allowing to get a speedup lower than 1. This action simulates the case of clusters linked with long distance network like Internet. -} -{\raggedright As a first step, the algorithm was run on a network consisting of two clusters containing fifty hosts each, totaling one hundred hosts. Various combinations of -the above factors have providing the results shown in Table 1 with a matrix size -ranging from Nx = Ny = Nz = 62 to 171 elements or from 62$^{3}$ = 238328 to -171$^{3}$ = 5,211,000 entries. -} +the above factors have providing the results shown in Table~\ref{tab.cluster.2x50} with a matrix size +ranging from Nx = Ny = Nz = 62 to 171 elements or from $62^{3} = \np{238328}$ to +$171^{3} = \np{5211000}$ entries. -{\raggedright Then we have changed the network configuration using three clusters containing respectively 33, 33 and 34 hosts, or again by on hundred hosts for all the clusters. In the same way as above, a judicious choice of key parameters has -permitted to get the results in Table 2 which shows the speedups less than 1 with +permitted to get the results in Table~\ref{tab.cluster.3x33} which shows the speedups less than 1 with a matrix size from 62 to 100 elements. -} -{\raggedright In a final step, results of an execution attempt to scale up the three clustered -configuration but increasing by two hundreds hosts has been recorded in Table 3. -} +configuration but increasing by two hundreds hosts has been recorded in Table~\ref{tab.cluster.3x67}. -{\raggedright Note that the program was run with the following parameters: -} -%{\raggedright -\textbullet{} \textbf {SMPI parameters:} -%} +\paragraph*{SMPI parameters} \begin{itemize} - \item HOSTFILE : Hosts file description. + \item HOSTFILE: Hosts file description. \item PLATFORM: file description of the platform architecture : clusters (CPU power, -... ) , intra cluster network description, inter cluster network (bandwidth bw , -lat latency , ... ). +\dots{}), intra cluster network description, inter cluster network (bandwidth bw, +lat latency, \dots{}). \end{itemize} -%{\raggedright -\textbullet{} \textbf {Arguments of the program:} -%} +\paragraph*{Arguments of the program} \begin{itemize} \item Description of the cluster architecture; \item Maximum number of internal and external iterations; \item Internal and external precisions; - \item Matrix size NX , NY and NZ; + \item Matrix size NX, NY and NZ; \item Matrix diagonal value = 6.0; \item Execution Mode: synchronous or asynchronous. \end{itemize} -\textbf{Table 1} - -\textit{{\scriptsize 2 clusters X 50 nodes}} -\includegraphics[width=209pt]{img-1.eps} - -\textbf{Table 2} - -\textit{{\scriptsize 3 clusters X 33 n\oe{}uds}} -\includegraphics[width=209pt]{img-1.eps} -\textbf{Table 3} - -\textit{{\scriptsize 3 clusters X 67 noeuds}} -\includegraphics[width=128pt]{img-2.eps} - -{\raggedright -\textbf{Interpretations and comments} -} +\begin{table} + \centering + \caption{2 clusters X 50 nodes} + \label{tab.cluster.2x50} + \AG{Les images manquent dans le dépôt Git. Si ce sont vraiment des tableaux, utiliser un format vectoriel (eps ou pdf), et surtout pas de jpeg!} + \includegraphics[width=209pt]{img1.jpg} +\end{table} + +\begin{table} + \centering + \caption{3 clusters X 33 nodes} + \label{tab.cluster.3x33} + \AG{Le fichier manque.} + \includegraphics[width=209pt]{img2.jpg} +\end{table} + +\begin{table} + \centering + \caption{3 clusters X 67 nodes} + \label{tab.cluster.3x67} + \AG{Le fichier manque.} +% \includegraphics[width=160pt]{img3.jpg} + \includegraphics[scale=0.5]{img3.jpg} +\end{table} + +\paragraph*{Interpretations and comments} -{\raggedright After analyzing the outputs, generally, for the configuration with two or three -clusters including one hundred hosts (Tables 1 and 2), some combinations of the +clusters including one hundred hosts (Tables~\ref{tab.cluster.2x50} and~\ref{tab.cluster.3x33}), some combinations of the used parameters affecting the results have given a speedup less than 1, showing the effectiveness of the asynchronous performance compared to the synchronous mode. -} -{\raggedright -In the case of a two clusters configuration, Table 1 shows that with a -deterioration of inter cluster network set with 5 Mbits/s of bandwidth, a latency +In the case of a two clusters configuration, Table~\ref{tab.cluster.2x50} shows that with a +deterioration of inter cluster network set with \np[Mbits/s]{5} of bandwidth, a latency in order of a hundredth of a millisecond and a system power of one GFlops, an -efficiency of about 40\% in asynchronous mode is obtained for a matrix size of 62 -elements . It is noticed that the result remains stable even if we vary the -external precision from E -05 to E-09. By increasing the problem size up to 100 -elements, it was necessary to increase the CPU power of 50 \% to 1.5 GFlops for a +efficiency of about \np[\%]{40} in asynchronous mode is obtained for a matrix size of 62 +elements. It is noticed that the result remains stable even if we vary the +external precision from \np{E-5} to \np{E-9}. By increasing the problem size up to 100 +elements, it was necessary to increase the CPU power of \np[\%]{50} to \np[GFlops]{1.5} for a convergence of the algorithm with the same order of asynchronous mode efficiency. Maintaining such a system power but this time, increasing network throughput -inter cluster up to 50 Mbits /s, the result of efficiency of about 40\% is -obtained with high external precision of E-11 for a matrix size from 110 to 150 -side elements . -} +inter cluster up to \np[Mbits/s]{50}, the result of efficiency of about \np[\%]{40} is +obtained with high external precision of \np{E-11} for a matrix size from 110 to 150 +side elements. -{\raggedright -For the 3 clusters architecture including a total of 100 hosts, Table 2 shows +For the 3 clusters architecture including a total of 100 hosts, Table~\ref{tab.cluster.3x33} shows that it was difficult to have a combination which gives an efficiency of -asynchronous below 80 \%. Indeed, for a matrix size of 62 elements, equality +asynchronous below \np[\%]{80}. Indeed, for a matrix size of 62 elements, equality between the performance of the two modes (synchronous and asynchronous) is -achieved with an inter cluster of 10 Mbits/s and a latency of E- 01 ms. To -challenge an efficiency by 78\% with a matrix size of 100 points, it was +achieved with an inter cluster of \np[Mbits/s]{10} and a latency of \np{E-1} ms. To +challenge an efficiency by \np[\%]{78} with a matrix size of 100 points, it was necessary to degrade the inter cluster network bandwidth from 5 to 2 Mbit/s. -} -{\raggedright -A last attempt was made for a configuration of three clusters but more power -with 200 nodes in total. The convergence with a speedup of 90 \% was obtained -with a bandwidth of 1 Mbits/s as shown in Table 3. -} +A last attempt was made for a configuration of three clusters but more powerful +with 200 nodes in total. The convergence with a speedup of \np[\%]{90} was obtained +with a bandwidth of \np[Mbits/s]{1} as shown in Table~\ref{tab.cluster.3x67}. \section{Conclusion} +CONCLUSION + +The experimental results on executing a parallel iterative algorithm in +asynchronous mode on an environment simulating a large scale of virtual +computers organized with interconnected clusters have been presented. +Our work has demonstrated that using such a simulation tool allow us to +reach the following three objectives: + +\newcounter{numberedCntD} +\begin{enumerate} +\item To have a flexible configurable execution platform resolving the +hard exercise to access to very limited but so solicited physical +resources; +\item to ensure the algorithm convergence with a raisonnable time and +iteration number ; +\item and finally and more importantly, to find the correct combination +of the cluster and network specifications permitting to save time in +executing the algorithm in asynchronous mode. +\setcounter{numberedCntD}{\theenumi} +\end{enumerate} +Our results have shown that in certain conditions, asynchronous mode is +speeder up to 40 \% than executing the algorithm in synchronous mode +which is not negligible for solving complex practical problems with more +and more increasing size. + + Several studies have already addressed the performance execution time of +this class of algorithm. The work presented in this paper has +demonstrated an original solution to optimize the use of a simulation +tool to run efficiently an iterative parallel algorithm in asynchronous +mode in a grid architecture. - -% An example of a floating figure using the graphicx package. -% Note that \label must occur AFTER (or within) \caption. -% For figures, \caption should occur after the \includegraphics. -% Note that IEEEtran v1.7 and later has special internal code that -% is designed to preserve the operation of \label within \caption -% even when the captionsoff option is in effect. 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Daly, \emph{A Guide to \LaTeX}, 3rd~ed.\hskip 1em plus -% 0.5em minus 0.4em\relax Harlow, England: Addison-Wesley, 1999. -% -%\end{thebibliography} - +\bibliography{hpccBib} - - -% that's all folks \end{document} - +%%% Local Variables: +%%% mode: latex +%%% TeX-master: t +%%% fill-column: 80 +%%% ispell-local-dictionary: "american" +%%% End: