Speed difference

Hello everyone !

I have got some strange things about a part of a program. I need to pick terrestrial data from a global grid (720,360). For a first file which contains some 102 years,
this part is very fast (1-2 min) whereas when I use an other file of 130 years, it takes more than 2-3 hours. So I've tried each one with 100 years, the difference of
speed is the same. I've looked for the origins and finally, I've found the part which was so long. Here the minimum script which shows the problem :

"begin

latlon = asciiread("/Users/adrien/data/PARAMETERS/gridout.cru.data",(/67420,2/),"float") ; loading the grid of terrestrial points
lat = latlon(:,1)
lon = latlon(:,0)
print("grid data read")

print("TMP")
a = addfile("/Users/adrien/data/INPUT/cru_ts_2_10.1901-2002.tmp.nc","r") ; loading the temperature for the global grid
tmp1 = a->tmp(0:1199,:,:) ; I've just take the 100 first years

latit = a->lat ; latitude and longitude
longit = a->lon

tmp2=(/tmp1(:,ind(latit.eq.lat(0)),ind(longit.eq.lon(0)))/)
;tmp2=fspan(0.,1199.,1200)
printVarSummary(tmp2)

intmp=new((/67420,1200/),float)
do ipt=0,67420-1
  ;intmp(ipt,:)=tmp1(:,ind(latit.eq.lat(ipt)),ind(longit.eq.lon(ipt))) ; the initial command
  ;tmp2=tmp1(:,ind(latit.eq.lat(ipt)),ind(longit.eq.lon(ipt))) ; first part : picking the temperature of the point ; alone this command is very fast
  intmp(ipt,:)=(/tmp2/) ; second part : WHERE I LOOSE ALL THE SPEED
  print("tmp : "+ipt) ; in order to see the speed
end do

end"

Variable: tmp2
Type: float
Total Size: 4800 bytes
            1200 values
Number of Dimensions: 1
Dimensions and sizes: [1200]
Coordinates:
Number Of Attributes: 1
  _FillValue : 1e+20

So the problem appears when I assign all the values to one point (lat,lon) even if I use a constant vector from the first point. But when I'm using a other vector
(fspan(1.,1199.,1200)) of same size and same type (float) as it's shown by printVarSummary(), it's becoming faster (>50 times faster). I was thinking every float
vector would have a same "behavior". I can't understand why the treatment is not the same one. Perhaps, I did something wrong. If somebody has a gimmick to
make it faster. I can wait but I will be using it 4 times in the program, and I should use the program more than 50 times, so it would be better to have something
fast...

Thanks

Adrien Mauss
mauss_at_wisc.edu

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Received on Fri Feb 23 2007 - 11:42:30 MST