Hi Hongtao, ARPACK will not run in parallel. In the parallel you can only use ModifiedArnoldi. If you need ARPACK, than you can have the build with MPI On, but you need to run the solver in serial. Stan <http://www.pw.edu.pl/> On 10.05.2024 13:54, Sherwin, Spencer J wrote:

HI Hongtao,

You can compile Nektar++ without the NEKTAR_USE_MPI flag, or go into ccmake from  your builds directory and toggle off NEKTAR_USE_MPI, reconfigure and this should then generate a configuration wtihouth mpi.

Alternatively you can try running “ModifiedArnoldi” instead of Arpack. I think that does run in parallel.

Cheers,

Spencer.

*From: *nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of 🌸那慢慢🌸<2644878715@qq.com> *Date: *Friday, 10 May 2024 at 12:37 *To: *nektar-users <nektar-users@imperial.ac.uk> *Subject: *[Nektar-users] ARPACK is not set-up for parallel execution

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Dear nektar++ users and developers,

I get the error "ARPACK is not set-up for parallel execution" when running the incompressbile flow solver in parallel with MPI，but in the file build/CMakeCache.tst have a line saying:NEKTAR_USE_MPI:BOOL=ON.How do I fix this?

Hongtao Cheng

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Hi Hongtao, Here is an examplpe on how to use ModifiedArnoldi method in linear stability analysis. (You also need to set the correct EvolutionOperator for your problem) <SOLVERINFO> <I PROPERTY="SolverType" VALUE="VelocityCorrectionScheme" /> <I PROPERTY="EQTYPE" VALUE="UnsteadyNavierStokes" /> <I PROPERTY="EvolutionOperator" VALUE="Direct" /> <I PROPERTY="Projection" VALUE="Continuous" /> <I PROPERTY="GlobalSysSoln" VALUE="XxtMultiLevelStaticCond" /> <I PROPERTY="TimeIntegrationMethod" VALUE="IMEXOrder2" /> <I PROPERTY="Driver" VALUE="ModifiedArnoldi" /> <I PROPERTY="ModeType" VALUE="HalfMode" /> <I PROPERTY="HOMOGENEOUS" VALUE="1D" /> <I PROPERTY="SpectralVanishingViscositySpectralHP" VALUE="DGKernel"/> </SOLVERINFO> To run in parallel, you can use the following command mpirun -np 64 IncNavierStokesSolver airfoil.xml airfoilc.xml Ankang Gao -----Original Messages----- From:🌸那慢慢🌸 <2644878715@qq.com> Send time:Wednesday, 05/15/2024 12:44:17 To: "Sherwin, Spencer J" <s.sherwin@imperial.ac.uk>, nektar-users <nektar-users@imperial.ac.uk> Subject: [Nektar-users] 回复： ARPACK is not set-up for parallel execution Dear nektar++ users and developers, Sorry to bother you again. Maybe I didn't express my question clearly. I want to use MPI to run the solver in parallel to improve computational speed. When I enter the command $/IncNavierStokesSolver Cylinder.xml Cylinder_Adjoint.xml, the error "ARPACK is not set-up for parallel execution" pops up. I have selected "use MPI" during the cmake process, and in the file build/CMakeCache.tst have a line saying: NEKTAR-USE-MPI: BOOL=ON. I would like to know how to use mpi to run IncNavierStokesSolver in parallel to solve stability_Adjoint. As you said,to replace "Arpack" in condition.xml with "ModifiedArnoldi" instead? Hongtao Cheng ------------------ 原始邮件 ------------------ 发件人: "Sherwin, Spencer J" <s.sherwin@imperial.ac.uk>; 发送时间: 2024年5月10日(星期五) 晚上7:54 收件人: "🌸那慢慢🌸"<2644878715@qq.com>;"nektar-users"<nektar-users@imperial.ac.uk>; 主题: Re: [Nektar-users] ARPACK is not set-up for parallel execution HI Hongtao, You can compile Nektar++ without the NEKTAR_USE_MPI flag, or go into ccmake from your builds directory and toggle off NEKTAR_USE_MPI, reconfigure and this should then generate a configuration wtihouth mpi. Alternatively you can try running “ModifiedArnoldi” instead of Arpack. I think that does run in parallel. Cheers, Spencer. From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of 🌸那慢慢🌸 <2644878715@qq.com> Date: Friday, 10 May 2024 at 12:37 To: nektar-users <nektar-users@imperial.ac.uk> Subject: [Nektar-users] ARPACK is not set-up for parallel execution | This email from 2644878715@qq.com originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list to disable email stamping for this address. | Dear nektar++ users and developers, I get the error "ARPACK is not set-up for parallel execution" when running the incompressbile flow solver in parallel with MPI，but in the file build/CMakeCache.tst have a line saying:NEKTAR_USE_MPI:BOOL=ON.How do I fix this? Hongtao Cheng