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Re: Accelerating a one-line program doing matrix multiplication [message #72681 is a reply to message #72680]

Tue, 28 September 2010 06:10

natha
Messages: 482
Registered: October 2007

Senior Member

Concatenation is a very slow action in IDL and, if you are copying
memory, the time of computation increases...
If v0, v1, v2 and v3 are each of them 3-element vectors then you will
not see the difference. TEMPORARY function is great when you are
copying large arrays. I think you can not improve your code because
the problem is the matrix multiplication and you can not change that.
Try putting timers to see what's the time to compute each instruction.

tt=SYSTIME(/SEC)
aux=[[v1],[v2],[v3]]
PRINT, SYSTIME(/SEc)-tt

tt=SYSTIME(/SEC)
aux=aux # vc
PRINT, SYSTIME(/SEC)-tt

etc.

Cheers,
nata

On Sep 28, 2:17 am, Axel M <axe...@gmail.com> wrote:
> On 27 Sep., 15:31, nata <bernat.puigdomen...@gmail.com> wrote:
>
>> You can use the TEMPORARY function if you can set the input to
>> undefined...
>> When you do [[v1],[v2],[v3]] you are duplicating data. v1, v2 and v3
>> are copied and you are not conserving memory.
>
>> You could try:
>> RETURN, [[TEMPORARY(v1)],[TEMPORARY(v2)],[TEMPORARY(v3)]] # vc +
>> REBIN(v0, SIZE(vc, /DIMENSIONS))
>
>> Cheers,
>> nata
>
> Thanks nata.
>
> v0, v1, v2 and v3 are each of them 3-element vectors. I can add that
> but, as I understand it, it will only save the place of 12 floating
> values in memory (48 bytes?).
>
> But I am happy that you did not see any other obvious thing. I started
> feeling depressed seeing that I am not being able to improve this
> single line of code... maybe it is ok, and the whole thing is just
> slow...? ahh.

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[Message index]

		Re: Accelerating a one-line program doing matrix multiplication By: Axel Martínez on Wed, 29 September 2010 03:48
		Re: Accelerating a one-line program doing matrix multiplication By: Axel Martínez on Wed, 29 September 2010 03:22
		Re: Accelerating a one-line program doing matrix multiplication By: rogass on Tue, 28 September 2010 23:57
		Re: Accelerating a one-line program doing matrix multiplication By: Jeremy Bailin on Tue, 28 September 2010 08:31
		Re: Accelerating a one-line program doing matrix multiplication By: natha on Tue, 28 September 2010 06:10
		Re: Accelerating a one-line program doing matrix multiplication By: Axel Martínez on Mon, 27 September 2010 23:17
		Re: Accelerating a one-line program doing matrix multiplication By: natha on Mon, 27 September 2010 06:31
		Re: Accelerating a one-line program doing matrix multiplication By: rogass on Wed, 29 September 2010 07:49

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