| Speed problem [message #42813] |
Wed, 23 February 2005 10:22  |
lloyd
Messages: 16
Registered: February 2003
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Junior Member |
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Hi
Can anyone help me speed up this piece of code. I've hear that using
histograms might be good, any ideas?
This piece of code takes a point centered at [pixel_z,pixel_y] and
looks for all detections within a 'radius'. The position of these
detections are defined by two arrays, z and y, giving their
coordinates. After this other things are done but this isn't a problem.
The really slow part is the pt1 where section. This identifies from the
arrays of 200,000 points, the points which lie in a box +-radius in y
and z. Then the coners are removed using then next where condition.
for pixel_y=uint(min(y)),roundup(max(y))-1 do begin
for pixel_z=uint(min(z)),roundup(max(z))-1 do begin
pt1 = where(y ge pixel_y-radius and y le pixel_y+radius and z ge
pixel_z-radius and z le pixel_z+radius)
if pt1[0] ne -1 then begin
b = where((y[pt1]-pixel_y)^2+(z[pt1]-pixel_z)^2 le radius^2)
if b[0] ne -1 then begin
a = pt1[b]
w = weight(SQRT((y[a]-pixel_y)^2+(z[a]-pixel_z)^2),FWHM/3.0)
m[(pixel_y-uint(min(y))),(pixel_z-uint(min(z)))] = total(w*s[a])
endif
endif
endfor
endfor
Any help would be greatly appriciated
Lloyd
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| Re: Speed problem [message #42900 is a reply to message #42813] |
Wed, 02 March 2005 10:19  |
Vince Hradil
Messages: 574
Registered: December 1999
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Senior Member |
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Why do you even do the first where? Why not just do:
b = where( (y-pixel_y)^2+(z-pixel_z)^2 le radius^2 ) ?
Anyway, Your code only takes me about 20 ms?
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