[ncl-talk] Plot values with gsn_add_text takes unreasonable time

[Mary Haley]

Rabah,

There are a series of issues with your script, but not all of them have to
do with why your code is taking so long.

1. You have mpMaxLatF and mpMinLatF set to the same value.

2. You've set gsnDraw to False, which will cause no text strings to be
added:

  txres at gsnDraw      =  False                   ; do not draw the plot

3. The txres at txFontThicknessF = 10 is going to cause your text strings to
be 10x as thick. Do you want this on top of the text being bold-faced?

4. You are adding almost 260,000 strings to the plot. Is what you mean to
do?

5. You are constructing the lat2d/lon2d arrays in two separate do loops.
You can make this code simpler by using "conform_dims".

6. Using gsn_add_text is going to cause 259920 graphical objects to be
created, because one has to be added for every string you create. This can
get very memory intensive.

If you are only planning to draw this one plot and not resize it later,
then I suggest using gsn_text instead of gsn_add_text.  This will prevent
the individual objects from being created, and will run faster.

See the attached script. I didn't clean up the code to fix the various
warnings from setting contour resources when you are only creating a map
script, because I figured you were in the middle of debugging this.  But, I
did clean it up to make it run faster.  This script took about 71 seconds
on my Mac.  If you take out the "txFontThicknessF" setting, then it runs in
about 62 seconds.

Note that I put the "gsn_text" call inside a single do loop.  This seems to
run faster than using a double do loop, or no do loop at all.  I think this
has to do with trying to add 259,000+ strings to a plot all at once versus
adding each string one at a time.  Instead, I'm adding 360 strings at a
time, for each 720 iterations, which seems to be a happy balance.

--Mary



On Sun, Jul 27, 2014 at 1:25 AM, Rabah Hachelaf <hachelaf at sca.uqam.ca>
wrote:

> Hi NCL users,
>
> I am using the ncl script below to plot temperature values from GFS data,
> this script works great when i regrid my data to a lower resolution.
> but when i want plotting the whole data (720 x 361 values) and after more
> than 3 hours, ncl still running without generate any image or error message.
> this very strange since NCL is supposed to be a powerful tool.
>
> Have you any suggest to this problem.
>
> Thanks a lot.
>
> Rabah
>
> ;************************************************
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> ;************************************************
>  a = addfile("gfs.t00z.pgrb2f00.grib2","r")
>     lon = a->lon_0
>     lat = a->lat_0
>     tt      = short2flt(a->TMP_P0_L100_GLL0({100000},:,:))
>     tt = (/tt-273/)
>
> lat2d= new((/361,720/),float)
> ;********* create 2D lat lon
> do l=0,719
>  lat2d(:,l)=lat(:)
> end do
>
> lon2d= new((/361,720/),float)
> do l=0,360
>  lon2d(l,:)=lon(:)
> end do
> ;******************************************
> wks_type="png"
>
>   wks_type at wkWidth = 4000
>    wks_type at wkHeight = 4000
>
>   wks = gsn_open_wks(wks_type,"plot_val")
>   gsn_define_colormap(wks,"gui_default")
>
>   res = True               ; plot mods desired
> res at pmTickMarkDisplayMode = "Always"
>   res at mpProjection      = "Mercator"       ; choose projection
>   res at mpGridAndLimbOn   = False             ; turn on lat/lon lines
>   res at mpPerimOn         = True             ; turn off box around plot
>   res at mpGridLatSpacingF = 45.               ; spacing for lat lines
>   res at mpGridLonSpacingF = 45.               ; spacing for lon lines
>   res at mpFillOn          = False
>    res at mpLimitMode  = "LatLon"
>    res at mpMinLatF            =   85.0
>     res at mpMaxLatF            =85.0
>     res at mpMinLonF            = -180
>     res at mpMaxLonF            = 180
>
>   res at cnFillOn          = False              ; color plot desired
>   res at cnLineLabelsOn    = False             ; turn off contour lines
>
>   res at vpXF            = 0                 ; make plot bigger
>   res at vpYF            = 1
>   res at vpWidthF        = 1
>   res at vpHeightF       = 1
> map = gsn_csm_map(wks,res)
>   txres               = True
>   txres at txFontQuality = True
>   txres at txFontHeightF = 0.00125
>   txres at txFont        = "helvetica-bold"
>   txres at txFontColor =1
>   txres at txFontThicknessF= 10
>   txres at gsnDraw      =  False                   ; do not draw the plot
>   txres at gsnFrame     =  False
> text = gsn_add_text(wks,map,sprintf("%2.0f", tt) , lon2d, lat2d,txres)
> draw(wks)      ; Now draw map with text strings and
> frame(wks)     ; advance the frame
> end
> --
> ------------------------------
> Cordialement,
> Best regards,
> Rabah Hachelaf
>
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