Model runs slow (Following largest:{(e_we)/100) * ((e_sn)/100) + smallest (e_we)/25) * ((e_sn)/25)/2 }Rule)

[Aakanksha Agrawal]

HI,WRF forum!
I met a problem when I tried to run a wrf model. I am using mpirun -np 72 ./wrf.exe, i tried with mpirun -np 96./wrf.exe, but my model runs very slow almost 1 hours simulation take 2.5 hors to complete. How can choose the effective no. of processor for faster run. Currently m following:
For your largest-sized domain(e_we)/100) * ((e_sn)/100) = least amount of processors you should use.
For your smallest-sized domain(e_we)/25) * ((e_sn)/25) = most amount of processors you should use.
this rule to choose the no. of processors but still its low. I am attaching my namelist.input file & job script. I request you to kindly look into it. and tell me what changes should be made for faster run.

Thankyou

 

[BHajni]

Hi,

Unfortunately the smallest grid size is the driver of the number of processors since for calculations the WRF tiles up the model area and those tiles must produce physically consistent results, hence the limit to ((e_we)/25) * ((e_sn)/25). Over defining the number of processors will slow the calculations.

The old post on processes is only valid for number of processes and not number of processors.That is an important distinction. Back when the tiling numerics were developped and the rule of thumb for calculation was made processors usually had 1 core, nowdays closer to 32 or even more.

For your domain, the maximum number of processes should be 50, so that mpirun -np 50 ./wrf.exe. Also your attached run script uses 15 processors and 40 threads, that results in 600 processes, that is just wrong for a domain size of 193x162.

Hope this helps.

 

[Aakanksha Agrawal]

Oh sorry I attached trial run script here. Thank you for information. I will try with mpirun -np 50 ./wrf.exe. i hope it will work. I will update if it run faster. Thank you!!

 

[Aakanksha Agrawal]

I tried with mpirun -np 50 ./wrf.exe, but still for 56 min simulation it took 1 hour 44 mins (almost double). What can be any alternative option for faster run.
I am attaching the snapshot for the same. Kindly look.