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Re: Fast matrix filling in IDL [message #13790 is a reply to message #13788] Sat, 12 December 1998 00:00 Go to previous messageGo to previous message
steinhh is currently offline  steinhh
Messages: 260
Registered: June 1994
Senior Member
A slight modification of David's program, and adding
my favourite speedup method:

PRO TEST
m = 1000
n = 500

array = Fltarr(m, n)
v = RandomU(seed, m)

time = systime(1)
FOR i=0,n-1 DO array[*,i] = v
Print, 'Time for Loop: ', systime(1) - time

time = systime(1)
vector = Replicate(1, n)
array = v ## vector
Print, 'Time for Matrix Operations: ', systime(1) - time

time = systime(1)
array = rebin(reform(v,m,1,/overwrite),m,n,/sample)
print, 'Time for Rebin Operations: ', systime(1) - time
END

On { alpha OSF unix 5.2 Oct 30 1998}, this gives:

Time for Loop: 0.27343702
Time for Matrix Operations: 0.093750000
Time for Rebin Operations: 0.067382932

Note that the relative speeds can vary quite a lot on
different architectures.

Regards,

Stein Vidar

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