[ncl-talk] Slow code

[Guido Cioni]

Everyone here will tell you that using loops in NCL it’s not efficient :)
But from my experience I think that the main thing slowing you down is that you are using addfile at every iteration. 
Does creating a whole file and reading that in the beginning would change what you are trying to compute? 

Guido Cioni
http://guidocioni.altervista.org <http://guidocioni.altervista.org/> 

> On 12 Jan 2016, at 15:35, Michael Notaro <mnotaro at wisc.edu> wrote:
> 
> Does anyone have a recommendation to speed up my code?
> It's been running for a day now.  I put asterisks next to the real slow loop.
> Basically, that part is converting a large array of hourly data into daily data.
> Thanks, Michael
> 
> 
> mns=(/"01","02","03","04","05","06","07","08","09","10","11","12"/)
> ndays=(/31,28,31,30,31,30,31,31,30,31,30,31/)
> 
> data=new((/141,217,20,12,744/),float) ; hourly data
> data at _FillValue=1e+35
> data=1e+35
> 
> cnt=0
> do iyr=0,19
>   do im=0,11
>     prefix=(1980+iyr)+""+mns(im)
>     b=addfile("/volumes/data1/yafang/Downscaling/ACCESS1-0/historical/output/ACCESS_SRF."+(1980+iyr)+""+mns(im)+"0100.nc","r") ; read hourly SRF data
>     iy=b->iy
>     jx=b->jx
>     xlat=b->xlat
>     xlon=b->xlon
>     snow=b->snv ; liquid equiv of snow on ground
>     dims=dimsizes(snow)
>     nt=dims(0)
>     data(:,:,iyr,im,0:nt-1)=snow(iy|:,jx|:,time|:)
>     delete(snow)
>     delete(b)
>     delete(dims)
>     cnt=cnt+1
>   end do
> end do
> data at _FillValue=1e+20
> 
> daily=new((/141,217,20,12,31/),float) ; daily data per month
> daily at _FillValue=1e+35
> daily=1e+35
> 
> cnt=0
> do id=0,30
>   daily(:,:,:,:,id)=dim_avg(data(:,:,:,:,cnt:cnt+23)) ; convert hourly to daily data     ***** THIS PART IS SLOW *****
>   cnt=cnt+24
> end do
> 
> delete(data)
> 
> 
> 
> 
> Michael Notaro
> Associate Director
> Nelson Institute Center for Climatic Research
> University of Wisconsin-Madison
> Phone: (608) 261-1503
> Email: mnotaro at wisc.edu <mailto:mnotaro at wisc.edu>
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