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Re: Threads in IDL 7.0 [message #63116 is a reply to message #63115]

Mon, 27 October 2008 08:44

Bernhard Reinhardt
Messages: 26
Registered: October 2008

Junior Member

David Fanning wrote:
> Bernhard Reinhardt writes:
>
>> I have have read the Chapter "Multithreading in IDL" in the IDL-Help. As
>> far as I can see some IDL functions use threads.
>>
>> Basically I want to count elements of a big array that exceed a given
>> number.
>>
>> count=0
>> for i = 0, 200000 do begin
>> if array[i] ge 10. then count++
>> endfor
>
> How about something like this:
>
> indices = Where(array GE 10, count)

Well, I wasnï¿½t really precise. Iï¿½m not doing this on a 1d-array but on a
4d-array, where 2 dimensions are time and 2 dimensions are space. I try
to filter special events in time and count those on a 2d-map. Hereï¿½s the
code:

for i = 0, N_ELEMENTS(STRUC.data[*,0,0,0])-1 do begin
for j = 0, N_ELEMENTS(STRUC.data[0,*,0,0])-1 do begin
indices = Where(STRUC.data[i,j,*,*] GE 150., count)
freq [i,j]=count
endfor
endfor

Although the array data is quite big "where" only getï¿½s a small portion
to see of it. So thread-pool isnï¿½t invoked. => CPU-Usage still 50%

I also asked some more IDL-experienced colleagues about generating
threads manually but they also didnï¿½t know about anything like that :(

BUT using your method still brought me a gain of 3.6 times faster
execution :)

regards

Bernhard

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[Message index]

		Re: Threads in IDL 7.0 By: Allan Whiteford on Tue, 28 October 2008 08:45
		Re: Threads in IDL 7.0 By: Vince Hradil on Tue, 28 October 2008 07:31
		Re: Threads in IDL 7.0 By: Vince Hradil on Tue, 28 October 2008 06:01
		Re: Threads in IDL 7.0 By: Bernhard Reinhardt on Tue, 28 October 2008 01:28
		Re: Threads in IDL 7.0 By: David Fanning on Mon, 27 October 2008 11:07
		Re: Threads in IDL 7.0 By: Allan Whiteford on Mon, 27 October 2008 10:27
		Re: Threads in IDL 7.0 By: Heinz Stege on Mon, 27 October 2008 10:26
		Re: Threads in IDL 7.0 By: Allan Whiteford on Mon, 27 October 2008 10:23
		Re: Threads in IDL 7.0 By: Foldy Lajos on Mon, 27 October 2008 09:59
		Re: Threads in IDL 7.0 By: Allan Whiteford on Mon, 27 October 2008 09:46
		Re: Threads in IDL 7.0 By: Foldy Lajos on Mon, 27 October 2008 09:11
		Re: Threads in IDL 7.0 By: Bernhard Reinhardt on Mon, 27 October 2008 08:44
		Re: Threads in IDL 7.0 By: David Fanning on Mon, 27 October 2008 06:23

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