Segmentation fault

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Zhi Mao
Posts: 13
Joined: Wed Jun 17, 2020 11:34 am

Segmentation fault

Post by Zhi Mao » Tue Jul 28, 2020 9:21 am

Hello,
I am simulating a convective precipitation process over the Tibetan Plateau.I know steep terrain will cuase seg-fault(my rsl.error file show that),so I typed "ulimit -s unlimited",set time_step=4*DX,add smooth_cg_topo = .true. in the &domains section and set epssm = 0.2.But after I did that,the seg-fault still occurred.I can think of only one reason:I yerterday set dx=30000 for d01 and dx=10000 for d02 was OK,but today I just changed dx=12000 for d01 and dx=4000 for d02.Whether resolution will also cause seg-fault? The following are my namelist.wps and namelist.input.
Attachments
namelist.input
(3.93 KiB) Downloaded 11 times
namelist.wps
(1.28 KiB) Downloaded 8 times

Zhi Mao
Posts: 13
Joined: Wed Jun 17, 2020 11:34 am

Re: Segmentation fault

Post by Zhi Mao » Thu Jul 30, 2020 12:38 pm

I've solved the problems I've had,the seg-fault(or CFL errors) do not occur.BUT for the stability of the model,I set time_step=36 for d01(dx=12000,293x193 grids) and time_step=4 for d02(dx=4000,331x304 grids),it takes too much time.Although I typed "mpirun -np 64 ./wrf.exe",it could take more than ten hours to run one day.:(

Ming Chen
Posts: 1013
Joined: Mon Apr 23, 2018 9:42 pm

Re: Segmentation fault

Post by Ming Chen » Thu Jul 30, 2020 5:44 pm

Please set epssm = 0.9, 0.9, 0.9 in your nameless and increase time step.Please let me know whether this works.
WRF Help Desk

Zhi Mao
Posts: 13
Joined: Wed Jun 17, 2020 11:34 am

Re: Segmentation fault

Post by Zhi Mao » Fri Jul 31, 2020 11:10 am

Dear Ming,
I have done as you said,set epssm = 0.9, 0.9 and increase time step in namelist.input,but the seg-fault still occur.After that,I changed namelist.input many times until the model worked.Here are my final namelist.wps, namelist.input,and domain preview(the two black frames are d01 and d02).It maybe take a lot of time,although I typed "nohup mpirun -np 64 ./wrf.exe > nohup.log 2>&1 &".
Attachments
domain_preview.png
namelist.input
(3.95 KiB) Downloaded 9 times
namelist.wps
(1.28 KiB) Downloaded 7 times

Ming Chen
Posts: 1013
Joined: Mon Apr 23, 2018 9:42 pm

Re: Segmentation fault

Post by Ming Chen » Fri Jul 31, 2020 4:52 pm

Hi Zhi,
We are aware that many issues may arise due to the complex terrain and large topography gradient over the Tibetan Plateau.
We usually recommend avoiding high-resolution run over that region, and turn on damping options.
epssm and w_damping can be helpful in certain cases.
You may also try diff_opt =2, 2, which is more physically reasonable.
WRF Help Desk

Zhi Mao
Posts: 13
Joined: Wed Jun 17, 2020 11:34 am

Re: Segmentation fault

Post by Zhi Mao » Tue Aug 04, 2020 2:39 pm

Hi Ming,
Thanks for your valuable suggestions!
Because the area of d01 is so big, I changed the resolution dx=20000 for d01,but didn't change dx=4000 for d02.
This time I set epssm=0.9,0.9,w_damping=1 and diff_opt =2, 2.The time_step=3dx is fine for d01 and d02.
Now do I just need to wait for the model to complete the calculation? Although I may have to wait a long time.
Attachments
namelist.input
(3.95 KiB) Downloaded 11 times
namelist.wps
(1.28 KiB) Downloaded 10 times

Zhi Mao
Posts: 13
Joined: Wed Jun 17, 2020 11:34 am

Re: Segmentation fault

Post by Zhi Mao » Sat Aug 08, 2020 1:08 am

I've solved the problem.Because of large topography gradient over the South Tibetan Plateau,the resolution less than 6km is not OK.Thanks!

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