# Parallelize Navier Stokes with moving boundary **URL:** \ **Category:** General Discussion\ **Created:** [May 6, 2025, 1:18pm UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904 "2025-05-06T13:18:26Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![zxss](https://avatars.discourse-cdn.com/v4/letter/z/bc8723/32.png) [@zxss](https://community.freefem.org/u/zxss)\ **Post date:** [May 6, 2025, 1:18pm UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/1 "2025-05-06T13:18:26Z")
Dear all, I already implement the sequential version of NS equation with moving boundary in FreeFem++, the code is [sequential\_moving\_boundary.edp](https://community.freefem.org/uploads/short-url/rSany5pi0kxo4Scg40PQNx3qwsm.edp) (2.4 KB) Now I want to parallelize it using PETSc, just change little, for example changing matrix to Mat. And it shows error like this on my Windows machine ![c1bb8c642a48815c8c64dfe72fe8d0d](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/7/78a5430a1839ce0e3d70551a8b000e751bc4bab4.png) and the parallel version code is [parallel\_moving\_boundary.edp](https://community.freefem.org/uploads/short-url/lTqPrIJKrevzEnqYvdmXyuFYj0b.edp) (2.5 KB) Can anyone give me any advice? Many thanks. ---
**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\ **Post date:** [May 7, 2025, 5:58pm UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/2 "2025-05-07T17:58:38Z")
Your `A` is uninitialized line 59, so you need to fix that. ---
**Author:** ![zxss](https://avatars.discourse-cdn.com/v4/letter/z/bc8723/32.png) [@zxss](https://community.freefem.org/u/zxss)\ **Post date:** [May 8, 2025, 1:07am UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/3 "2025-05-08T01:07:49Z")
Thank you for your reminder, Professor. It’s a stupid mistake. I have fixed the initialization of Mat like this ![478ce636f6282860726af331927f13d](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/9/933795a23be038fb93e486c427aa335b54afb1df.png) However, there still exists error as shown below ![55fda1e1b5b2c1399e7a51dc1b076fb](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/a/a2e7307cba48147b5e8a999403f6ccd8ccfd260d.png) Do you know what’s wrong? Thanks a lot. [parallel\_moving\_boundary\_2.edp](https://community.freefem.org/uploads/short-url/bsRZZ249cm8TTPq2Vas1zvssugW.edp) (2.6 KB) ---
**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\ **Post date:** [May 8, 2025, 7:18am UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/4 "2025-05-08T07:18:11Z")
You are trying to initialize with the same macro a `Mat` with two fields and another one with three fields, hence the error. ---
**Author:** ![zxss](https://avatars.discourse-cdn.com/v4/letter/z/bc8723/32.png) [@zxss](https://community.freefem.org/u/zxss)\ **Post date:** [May 10, 2025, 12:46am UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/5 "2025-05-10T00:46:27Z")
Sorry for my late reply. Thank you very much for your reply. It’s another stupid mistake. Now I fix it as following ![aa02dfd0a5f492276e21a117fea2dc6](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/1/14f1c45e806957c589b7a5ad1fa00639dfda4205.png) And it’s the latest code [parallel\_moving\_boundary\_3.edp](https://community.freefem.org/uploads/short-url/u1PFHdfze3nTxuxirza1aHNIkSE.edp) (2.7 KB) However, there still exists error shown as ![caca6189208655252ba486e6d51f2d7](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/3/309b34d13d3b4e816ad7836b61ef84563ac924a4.png) Do you know the reason? ---
**Author:** ![zxss](https://avatars.discourse-cdn.com/v4/letter/z/bc8723/32.png) [@zxss](https://community.freefem.org/u/zxss)\ **Post date:** [May 10, 2025, 12:56am UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/6 "2025-05-10T00:56:30Z")
Sorry, I know the reason for the last error. It was because I entered the wrong file name. This time, the specific error occurred as the following ![caca6189208655252ba486e6d51f2d7](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/3/309b34d13d3b4e816ad7836b61ef84563ac924a4.png) Do you know its reason? ---
**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\ **Post date:** [May 10, 2025, 5:41am UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/7 "2025-05-10T05:41:42Z")
This is the exact same error. ---
**Author:** ![zxss](https://avatars.discourse-cdn.com/v4/letter/z/bc8723/32.png) [@zxss](https://community.freefem.org/u/zxss)\ **Post date:** [May 10, 2025, 6:02am UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/8 "2025-05-10T06:02:27Z")
Thank you very much for your reply. Now my code can be run [parallel\_moving\_boundary\_3.edp](https://community.freefem.org/uploads/short-url/nqw0fPYVer4XfVZEg8gTP4FKtBl.edp) (2.7 KB) But it looks not converge Apptainer\> ff-mpirun -n 10 parallel\_moving\_boundary\_3.edp -wg -v 0 ‘/usr/freefem/ff-petsc/r/bin/mpiexec’ -n 10 /usr/freefem/bin/FreeFem+±mpi -nw ‘parallel\_moving\_boundary\_3.edp’ -wg -v 0 KSP final norm of residual 4.42545e+15 KSP final norm of residual 2.2619e+15 NS Time: 0.001 KSP final norm of residual 1.03851e+16 KSP final norm of residual 3.69771e+15 NS Time: 0.002 KSP final norm of residual 1.58529e+16 KSP final norm of residual 7.00204e+15 ---
**Author:** ![zxss](https://avatars.discourse-cdn.com/v4/letter/z/bc8723/32.png) [@zxss](https://community.freefem.org/u/zxss)\ **Post date:** [May 10, 2025, 6:07am UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/9 "2025-05-10T06:07:11Z")
It can be run in my Linux machine with’ff-mpirun’, but it still exists errors on my computer machine with ‘mpiexec -n freefem+±mpi’ ---
**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\ **Post date:** [May 10, 2025, 6:35am UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/10 "2025-05-10T06:35:53Z")
Probably because you are using the default `tgv` value. ---
**Author:** ![zxss](https://avatars.discourse-cdn.com/v4/letter/z/bc8723/32.png) [@zxss](https://community.freefem.org/u/zxss)\ **Post date:** [May 10, 2025, 7:39am UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/11 "2025-05-10T07:39:22Z")
Thank you very much, professsor. I change ‘tgv=-1’, and then it truly converges ![Screenshot from 2025-05-10 08-39-04](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/a/a4792bd25cecb466fb7200546d9aa1fd0ca97c14.png) ---
**Author:** ![zxss](https://avatars.discourse-cdn.com/v4/letter/z/bc8723/32.png) [@zxss](https://community.freefem.org/u/zxss)\ **Post date:** [May 10, 2025, 7:12pm UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/12 "2025-05-10T19:12:37Z")
Dear professor, I have one last question, that is I find it calculates very slowly with ‘-pc\_type lu’, is there other options can accelerate? ---
**Author:** ![prj](https://avatars.discourse-cdn.com/v4/letter/p/ecae2f/32.png) [@prj](https://community.freefem.org/u/prj)\ **Post date:** [May 11, 2025, 5:07am UTC](https://community.freefem.org/t/parallelize-navier-stokes-with-moving-boundary/3904/13 "2025-05-11T05:07:40Z")
A proper preconditioner could help things out.