Re: NCL is getting slower when I call "user defined function" many times

Hi joowan,
Do loops can be very slow in ncl, use f90 wrapper script. Should solve your problem
Cheers

P. Shrestha

On Apr 22, 2013, at 6:31 PM, Joowan Kim <joowan.k@gmail.com> wrote:

> Dear NCL users
>
> I'm calculating the tropopause for temperature profiles using NCL's "do loop" and a user-defined function.
> The user-defined function works for a single temperature profile, and do loop call the function for each temperature profiles.
> There is an exactly same calculation ("just calling of a function I defined") in the do loop, so each step is expected to take a same time. However the do loop takes longer and longer time as it progresses.
>
> Here is the example
> (elapsed time (time1-time0) for each step keeps increasing)
> [joowan@rossby ttl_joowan]$ ncl main.ncl
> Copyright (C) 1995-2011 - All Rights Reserved
> University Corporation for Atmospheric Research
> NCAR Command Language Version 6.0.0
> The use of this software is governed by a License Agreement.
> See http://www.ncl.ucar.edu/ for more details.
> (0) loop i = 1 elapsed time: 4
> (0) loop i = 2 elapsed time: 5
> (0) loop i = 3 elapsed time: 7
> (0) loop i = 4 elapsed time: 9
> (0) loop i = 5 elapsed time: 10
> (0) loop i = 6 elapsed time: 11
> (0) loop i = 7 elapsed time: 13
> (0) loop i = 8 elapsed time: 14
> (0) loop i = 9 elapsed time: 15
> (0) loop i = 10 elapsed time: 17
> (0) loop i = 11 elapsed time: 19
> (0) loop i = 12 elapsed time: 20
> ...
> ...
> (0) loop i = 31 elapsed time: 52
> (0) loop i = 32 elapsed time: 54
>
> I tested this with the newest version 6.1.2, but it has the same problem.
> It is very strange because I never met this problem with NCL before.
> One thing I found is memory use keeps increase until unreasonable size. I guess "user defined function" doesn't return memory, so lots of calling it takes bigger memory and longer time. (If I directly do the calculation in the code, not using a user-defined function, that slow down does NOT happen.) But it is just my crude guess...
> It is a serious problem for me, because the do loop goes up to 3000 for model analysis, and the computation time grows exponentially.
> Is there any Known issue for this problem or treatment?
> Any comment will be appreciated.
>
> Thanks so much
>
> Best!
> Just in case, I attached my script and data
>
>
> Joowan
>
> P.S.
> I'm using
> Linux rossby.meteo.mcgill.ca 2.6.34.9-69.fc13.x86_64 #1 SMP Tue May 3 09:23:03 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux
> GCC version is "gcc version 4.4.5 20101112 (Red Hat 4.4.5-2) (GCC)"
>
>
> --
> Joowan Kim
> Atmospheric and Oceanic Sciences
> McGill University
> e-mail : joowan.kim@mail.mcgill.ca
> joowan.k@gmail.com
> <main.ncl>
> <ttl_joowan.ncl>
> <tprof_ERAI.dat>
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Received on Mon Apr 22 10:35:11 2013