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Re: Threads in IDL 7.0 [message #63091 is a reply to message #63088]

Tue, 28 October 2008 06:01

Vince Hradil
Messages: 574
Registered: December 1999

Senior Member

On Oct 27, 12:26 pm, Heinz Stege <public.215....@arcor.de> wrote:
> On Mon, 27 Oct 2008 16:44:29 +0100, Bernhard Reinhardt wrote:
>> Well, I wasn´t really precise. I´m 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. Here´s 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 get´s a small portion
>> to see of it. So thread-pool isn´t invoked. => CPU-Usage still 50%
>
>> I also asked some more IDL-experienced colleagues about generating
>> threads manually but they also didn´t know about anything like that :(
>
>> BUT using your method still brought me a gain of 3.6 times faster
>> execution :)
>
>> regards
>
>> Bernhard
>
> Please try the following command:
>
> freq=total(total(STRUC.data ge 150.,4,/integer),3,/integer)
>
> The IDL manual says, that TOTAL makes use of IDL’s thread pool. And
> there is no for-loop needed anymore...
>
> HTH, Heinz

So, which is faster?

freq = fix(total(total(transpose(struc.data,[2,3,0,1]) ge 150.,1),1))

or

freq=total(total(STRUC.data ge 150.,4,/integer),3,/integer)

TRANSPOSE or TOTAL over trailing dims?

Here's my quick (un-scientific) test:
(
IDL> arr = bytscl(randomu(sd, [100,101,102,103]))
IDL> t0 = systime(1) & help, total(total(arr,4,/integer),3,/integer) &
print, systime(1)-t0
<Expression> LONG64 = Array[100, 101]
0.45300007
IDL> t0 = systime(1) & help, total(total(transpose(arr,[2,3,0,1]),1,/
integer),1,/integer) & print, systime(1)-t0
<Expression> LONG64 = Array[100, 101]
1.5929999
IDL> print, !version
{ x86 Win32 Windows Microsoft Windows 7.0 Oct 25 2007 32 64}

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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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