are not available. In our experiments, we have tested different kinds of\r
preconditioners, but as it is not the subject of this paper, we will not\r
present results with many preconditioners. In practice, we have chosen to use a\r
-multigrid (mg) and successive over-relaxation (sor). For further details on the\r
+multigrid (MG) and successive over-relaxation (SOR). For further details on the\r
preconditioners in PETSc, readers are referred to~\cite{petsc-web-page}.\r
\r
\r
nb. cores & precond & \multicolumn{2}{c|}{FGMRES} & \multicolumn{2}{c|}{TSIRM CGLS} & \multicolumn{2}{c|}{TSIRM LSQR} & best gain \\ \r
\cline{3-8}\r
& & Time & \# Iter. & Time & \# Iter. & Time & \# Iter. & \\\hline \hline\r
- 2,048 & mg & 403.49 & 18,210 & 73.89 & 3,060 & 77.84 & 3,270 & 5.46 \\\r
- 2,048 & sor & 745.37 & 57,060 & 87.31 & 6,150 & 104.21 & 7,230 & 8.53 \\\r
- 4,096 & mg & 562.25 & 25,170 & 97.23 & 3,990 & 89.71 & 3,630 & 6.27 \\\r
- 4,096 & sor & 912.12 & 70,194 & 145.57 & 9,750 & 168.97 & 10,980 & 6.26 \\\r
- 8,192 & mg & 917.02 & 40,290 & 148.81 & 5,730 & 143.03 & 5,280 & 6.41 \\\r
- 8,192 & sor & 1,404.53 & 106,530 & 212.55 & 12,990 & 180.97 & 10,470 & 7.76 \\\r
- 16,384 & mg & 1,430.56 & 63,930 & 237.17 & 8,310 & 244.26 & 7,950 & 6.03 \\\r
- 16,384 & sor & 2,852.14 & 216,240 & 418.46 & 21,690 & 505.26 & 23,970 & 6.82 \\\r
+ 2,048 & MG & 403.49 & 18,210 & 73.89 & 3,060 & 77.84 & 3,270 & 5.46 \\\r
+ 2,048 & SOR & 745.37 & 57,060 & 87.31 & 6,150 & 104.21 & 7,230 & 8.53 \\\r
+ 4,096 & MG & 562.25 & 25,170 & 97.23 & 3,990 & 89.71 & 3,630 & 6.27 \\\r
+ 4,096 & SOR & 912.12 & 70,194 & 145.57 & 9,750 & 168.97 & 10,980 & 6.26 \\\r
+ 8,192 & MG & 917.02 & 40,290 & 148.81 & 5,730 & 143.03 & 5,280 & 6.41 \\\r
+ 8,192 & SOR & 1,404.53 & 106,530 & 212.55 & 12,990 & 180.97 & 10,470 & 7.76 \\\r
+ 16,384 & MG & 1,430.56 & 63,930 & 237.17 & 8,310 & 244.26 & 7,950 & 6.03 \\\r
+ 16,384 & SOR & 2,852.14 & 216,240 & 418.46 & 21,690 & 505.26 & 23,970 & 6.82 \\\r
\hline\r
\r
\end{tabular}\r
-\caption{Comparison of FGMRES and TSIRM with FGMRES for example ex15 of PETSc/KSP with two preconditioners (mg and sor) having 25,000 components per core on Juqueen ($\epsilon_{tsirm}=1e-3$, $max\_iter_{kryl}=30$, $s=12$, $max\_iter_{ls}=15$, $\epsilon_{ls}=1e-40$), time is expressed in seconds.}\r
+\caption{Comparison of FGMRES and TSIRM with FGMRES for example ex15 of PETSc/KSP with two preconditioners (MG and SOR) having 25,000 components per core on Juqueen ($\epsilon_{tsirm}=1e-3$, $max\_iter_{kryl}=30$, $s=12$, $max\_iter_{ls}=15$, $\epsilon_{ls}=1e-40$), time is expressed in seconds.}\r
\label{tab:03}\r
\end{center}\r
\end{table*}\r
Table~\ref{tab:03} shows the execution times and the number of iterations of\r
example ex15 of PETSc on the Juqueen architecture. Different numbers of cores\r
are studied ranging from 2,048 up-to 16,383 with the two preconditioners {\it\r
- mg} and {\it sor}. For those experiments, the number of components (or\r
+ MG} and {\it SOR}. For those experiments, the number of components (or\r
unknowns of the problems) per core is fixed at 25,000, also called weak\r
scaling. This number can seem relatively small. In fact, for some applications\r
that need a lot of memory, the number of components per processor requires\r
\r
%%NEW\r
\r
+{\bf example ex45/ksp à décrire et commenter en montrant que hypre est pourri avec cet exemple}\r
+\r
+\begin{table*}[htbp]\r
+\begin{center}\r
+\begin{tabular}{|r|r|r|r|r|r|r|r|} \r
+\hline\r
+\r
+ nb. cores & \multicolumn{2}{c|}{FGMRES/ASM} & \multicolumn{2}{c|}{TSIRM CGLS/ASM} & gain& \multicolumn{2}{c|}{FGMRES/HYPRE} \\ \r
+\cline{2-5} \cline{7-8}\r
+ & Time & \# Iter. & Time & \# Iter. & & Time & \# Iter. \\\hline \hline\r
+ 512 & 5.54 & 685 & 2.5 & 570 & 2.21 & 128.9 & 9 \\\r
+ 2048 & 14.95 & 1,560 & 4.32 & 746 & 3.48 & 335.7 & 9 \\\r
+ 4096 & 25.13 & 2,369 & 5.61 & 859 & 4.48 & >1000 & -- \\\r
+ 8192 & 44.35 & 3,197 & 7.6 & 1083 & 5.84 & >1000 & -- \\\r
+\r
+\hline\r
+\r
+\end{tabular}\r
+\caption{Comparison of FGMRES and TSIRM for ex45 of PETSc/KSP with two preconditioner (ASM and HYPRE) having 5,000 components per core on Curie ($\epsilon_{tsirm}=1e-10$, $max\_iter_{kryl}=30$, $s=12$, $max\_iter_{ls}=15$,$\epsilon_{ls}=1e-40$), time is expressed in seconds.}\r
+\label{tab:06}\r
+\end{center}\r
+\end{table*}\r
+\r
+\r
\subsection{Parallel nonlinear problems}\r
\r
With PETSc, linear solvers are used inside nonlinear solvers. The SNES\r
(Scalable Nonlinear Equations Solvers) module in PETSc implements easy to use\r
methods, like Newton-type, quasi-Newton or full approximation scheme (FAS)\r
-multigrid to solve systems of nonlinears equations. As the SNES is based on the\r
+multigrid to solve systems of nonlinears equations. As SNES is based on the\r
Krylov methods of PETSc, it is interesting to investigate if the TSIRM method is\r
-also efficient and scalable with non linear problems.\r
-\r
-\r
-\r
+also efficient and scalable with non linear problems. In PETSc, some examples\r
+are provided. An important criteria is the scalability of the initial code with\r
+classical solvers. Consequently, we have chosen two of these examples: ex14 and\r
+ex20. In ex14, the code solves the Bratu (SFI - solid fuel ignition) nonlinear\r
+partial difference equations in 3 dimension. In ex20, the code solves a 3\r
+dimension radiative transport test problem. For more details on these examples,\r
+interested readers are invited to see the code in the PETSc examples. For both\r
+these examples, a weak scaling case is chosen where processors have\r
+approximately a number of components equals to 100,000.\r
+\r
+In Table~\ref{tab:07} we report the result of our experiments for the example\r
+ex14 with the block Jacobi preconditioner. For TSIRM the CGLS algorithm is used\r
+to solve the minimization step. In this table, we can see that the number of\r
+iterations used by the linear solver is smaller with TSIRM compared with FGMRES.\r
+Consequently the execution times are smaller with TSIRM. The gain between TSIRM\r
+and FGMRES is around 6 and 7. The parameters of TSIRM are expressed in the\r
+caption of the table.\r
\r
\begin{table*}[htbp]\r
\begin{center}\r
\begin{tabular}{|r|r|r|r|r|r|} \r
\hline\r
\r
- nb. cores & \multicolumn{2}{c|}{FGMRES/BJAC} & \multicolumn{2}{c|}{TSIRM CGLS/BJAC} & gain \\ \r
+ nb. cores & \multicolumn{2}{c|}{FGMRES/BJAC} & \multicolumn{2}{c|}{TSIRM CGLS/BJAC} & gain \\ \r
\cline{2-5}\r
- & Time & \# Iter. & Time & \# Iter. & \\\hline \hline\r
- 1024 & 667.92 & 48,732 & 81.65 & 5,087 & 8.18 \\\r
- 2048 & 966.87 & 77,177 & 90.34 & 5,716 & 10.70\\\r
- 4096 & 1,742.31 & 124,411 & 119.21 & 6,905 & 14.61\\\r
- 8192 & 2,739.21 & 187,626 & 168.9 & 9,000 & 16.22\\\r
+ & Time & \# Iter. & Time & \# Iter. & \\\hline \hline\r
+ 1,024 & 159.52 & 11,584 & 26.34 & 1,563 & 6.06 \\\r
+ 2,048 & 226.24 & 16,459 & 37.23 & 2,248 & 6.08\\\r
+ 4,096 & 391.21 & 27,794 & 50.93 & 2,911 & 7.69\\\r
+ 8,192 & 543.23 & 37,770 & 79.21 & 4,324 & 6.86 \\\r
\r
\hline\r
\r
\end{tabular}\r
-\caption{Comparison of FGMRES and TSIRM for ex20 of PETSc/SNES with a Block Jacobi preconditioner having 100,000 components per core on Curie ($\epsilon_{tsirm}=1e-10$, $max\_iter_{kryl}=30$, $s=12$, $max\_iter_{ls}=15$, $\epsilon_{ls}=1e-40$), time is expressed in seconds.}\r
+\caption{Comparison of FGMRES and TSIRM for ex14 of PETSc/SNES with a Block Jacobi preconditioner having 100,000 components per core on Curie ($\epsilon_{tsirm}=1e-10$, $max\_iter_{kryl}=30$, $s=12$, $max\_iter_{ls}=15$, $\epsilon_{ls}=1e-40$), time is expressed in seconds.}\r
\label{tab:07}\r
\end{center}\r
\end{table*}\r
\r
+In Table~\cite{tab:08}, the results of the experiments with the example ex20 are\r
+reported. The block Jacobi preconditioner has also been used and CGLS to solve\r
+the minimization step for TSIRM. For this example, we can observ that the number\r
+of iterations for FMGRES increase drastically when the number of cores\r
+increases. With TSIRM, we can see that the number of iterations is initially\r
+very small compared to the FGMRES ones and when the number of cores increase,\r
+the number of iterations increases slighther with TSIRM than with FGMRES. For\r
+this example, the gain between TSIRM and FGMRES ranges between 8 with 1,024\r
+cores to more than 16 with 8,192 cores.\r
+\r
\begin{table*}[htbp]\r
\begin{center}\r
\begin{tabular}{|r|r|r|r|r|r|} \r
\hline\r
\r
- nb. cores & \multicolumn{2}{c|}{FGMRES/BJAC} & \multicolumn{2}{c|}{TSIRM CGLS/BJAC} & gain \\ \r
+ nb. cores & \multicolumn{2}{c|}{FGMRES/BJAC} & \multicolumn{2}{c|}{TSIRM CGLS/BJAC} & gain \\ \r
\cline{2-5}\r
- & Time & \# Iter. & Time & \# Iter. & \\\hline \hline\r
- 1024 & 159.52 & 11,584 & 26.34 & 1,563 & 6.06 \\\r
- 2048 & 226.24 & 16,459 & 37.23 & 2,248 & 6.08\\\r
- 4096 & 391.21 & 27,794 & 50.93 & 2,911 & 7.69\\\r
- 8192 & 543.23 & 37,770 & 79.21 & 4,324 & 6.86 \\\r
+ & Time & \# Iter. & Time & \# Iter. & \\\hline \hline\r
+ 1,024 & 667.92 & 48,732 & 81.65 & 5,087 & 8.18 \\\r
+ 2,048 & 966.87 & 77,177 & 90.34 & 5,716 & 10.70\\\r
+ 4,096 & 1,742.31 & 124,411 & 119.21 & 6,905 & 14.61\\\r
+ 8,192 & 2,739.21 & 187,626 & 168.9 & 9,000 & 16.22\\\r
\r
\hline\r
\r
\end{tabular}\r
-\caption{Comparison of FGMRES and TSIRM for ex14 of PETSc/SNES with a Block Jacobi preconditioner having 100,000 components per core on Curie ($\epsilon_{tsirm}=1e-10$, $max\_iter_{kryl}=30$, $s=12$, $max\_iter_{ls}=15$, $\epsilon_{ls}=1e-40$), time is expressed in seconds.}\r
+\caption{Comparison of FGMRES and TSIRM for ex20 of PETSc/SNES with a Block Jacobi preconditioner having 100,000 components per core on Curie ($\epsilon_{tsirm}=1e-10$, $max\_iter_{kryl}=30$, $s=12$, $max\_iter_{ls}=15$, $\epsilon_{ls}=1e-40$), time is expressed in seconds.}\r
\label{tab:08}\r
\end{center}\r
\end{table*}\r
\r
\r
+\r
+\r
+\r
+\r
+\r
+%%NEW\r
\subsection{Influence of parameters for TSIRM}\r
\r
+\begin{figure}[htbp]\r
+\centering\r
+ \includegraphics[angle=-90,width=0.5\textwidth]{ksp_tsirm_cgls_iter_total}\r
+\caption{Number of total iterations using two different methods for the minimization: LSQR and CGLS.}\r
+\label{fig:cgls-iter} \r
+\end{figure}\r
+\r
+\begin{figure}[htbp]\r
+\centering\r
+ \includegraphics[angle=-90,width=0.5\textwidth]{ksp_tsirm_cgls_time}\r
+\caption{Execution time in seconds using two different methods for the minimization: LSQR and CGLS.}\r
+\label{fig:cgls-time} \r
+\end{figure}\r
+\r
+\begin{figure}[htbp]\r
+\centering\r
+ \includegraphics[angle=-90,width=0.5\textwidth]{ksp_tsirm_inner_restarts_iter_total}\r
+\caption{Number of total iterations with variation of restarts in the inner solver FGMRES.}\r
+\label{fig:inner_restarts_iter_total} \r
+\end{figure}\r
+\r
+\begin{figure}[htbp]\r
+\centering\r
+ \includegraphics[angle=-90,width=0.5\textwidth]{ksp_tsirm_inner_restarts_time}\r
+\caption{Execution time in seconds with variation of restarts in the inner solver FGMRES.}\r
+\label{fig:inner_restarts_time} \r
+\end{figure}\r
+\r
+\begin{figure}[htbp]\r
+\centering\r
+ \includegraphics[angle=-90,width=0.5\textwidth]{ksp_tsirm_max_inner_iter}\r
+\caption{Number of total iterations with variation of number of inner iterations.}\r
+\label{fig:max_inner_iter} \r
+\end{figure}\r
+\r
+\begin{figure}[htbp]\r
+\centering\r
+ \includegraphics[angle=-90,width=0.5\textwidth]{ksp_tsirm_max_inner_time}\r
+\caption{Execution time in seconds with variation of number of inner iterations.}\r
+\label{fig:max_inner_time} \r
+\end{figure}\r
+\r
+\begin{figure}[htbp]\r
+\centering\r
+ \includegraphics[angle=-90,width=0.5\textwidth]{ksp_tsirm_maxiter_ls_iter}\r
+\caption{Number of total iterations with variation of number of iterations in the minimization process.}\r
+\label{fig:maxiter_ls_iter} \r
+\end{figure}\r
+\r
+\begin{figure}[htbp]\r
+\centering\r
+ \includegraphics[angle=-90,width=0.5\textwidth]{ksp_tsirm_maxiter_ls_time}\r
+\caption{Execution time in seconds with variation of number of iterations in the minimization process.}\r
+\label{fig:maxiter_ls_time} \r
+\end{figure}\r
+\r
+\begin{figure}[htbp]\r
+\centering\r
+ \includegraphics[angle=-90,width=0.5\textwidth]{ksp_tsirm_size_ls_iter}\r
+\caption{Number of total iterations with variation of the size of the least-squares problem in the minimization process.}\r
+\label{fig:size_ls_iter} \r
+\end{figure}\r
+\r
+\begin{figure}[htbp]\r
+\centering\r
+ \includegraphics[angle=-90,width=0.5\textwidth]{ksp_tsirm_size_ls_time}\r
+\caption{Execution time in seconds with variation of the size of the least-squares problem in the minimization process.}\r
+\label{fig:size_ls_time} \r
+\end{figure}\r
+\r
+%%ENDNEW\r
+\r
\r
\r
\r
