Hi Professor Ding, Did you get to the bottom of this. When selecting use MPI you typically have to configure the cmake process a couple of times if you are using the interactive version of cmake (ccmake?). Have you tried a fresh compilation since you may have just not activated the MPI side of things correctly. Cheers, Spencer. PS In the file builds/CMakeCache.tst it should have a line saying: NEKTAR_USE_MPI:BOOL=ON Spencer Sherwin FREng, FRAeS Head of Aerodynamics Section, Director of Research Computing Service, Professor of Computational Fluid Mechanics, Department of Aeronautics, South Kensington Campus, Imperial College London, SW7 2AZ, UK Phone: +44 (0)20 7594 5052 http://www.imperial.ac.uk/people/s.sherwin/ On 13 Aug 2020, at 09:31, Professor Ding、 <ztdepyahoo@163.com<mailto:ztdepyahoo@163.com>> wrote: This email from ztdepyahoo@163.com<mailto:ztdepyahoo@163.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<https://spam.ic.ac.uk/SpamConsole/Senders.aspx> to disable email stamping for this address. Dear friends: I have select "use MPI" during the cmake process. but when i run incompressbile flow solver, it still gives me the error of "A parallel solver must be used when run in parallel". How to resolve this problem. Regards <https://maas.mail.163.com/dashi-web-extend/html/proSignature.html?ftlId=1&name=Professor+Ding%E3%80%81&uid=ztdepyahoo%40163.com&iconUrl=https%3A%2F%2Fmail-online.nosdn.127.net%2Fqiyelogo%2FdefaultAvatar.png&items=%5B%22ztdepyahoo%40163.com%22%5D> [https://mail-online.nosdn.127.net/qiyelogo/defaultAvatar.png] Professor Ding、 ztdepyahoo@163.com 签名由 网易邮箱大师<https://mail.163.com/dashi/dlpro.html?from=mail81> 定制 _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk<mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users