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Re: Accelerating a one-line program doing matrix multiplication [message #72743 is a reply to message #72696]

Thu, 30 September 2010 08:03

pgrigis
Messages: 436
Registered: September 2007

Senior Member

On Sep 30, 10:59 am, Paolo <pgri...@gmail.com> wrote:
> [skip]
>
>
>
>> FUNCTION vc2rc_accel, v0,v1,v2,v3,vc
>> npoints = (SIZE(vc, /DIMENSIONS))[1]
>> for i=0L, npoints-1 DO BEGIN
>> vc[*,i] = vc[0,i] * v1 + vc[1,i] * v2 + vc[2,i] * v3 + v0
>> endfor
>> RETURN, vc
>> END
>
> No, that's using a for loop - that's why it is slow.
> You want something like this (no loops):
>
> vc0=vc[0,*]
> vc1=vc[1,*]
> vc2=vc[2,*]
> vc[0,*]=vc0*v1[0]+vc1*v2[0]+vc3*v3[0]
> vc[1,*]=vc0*v1[1]+vc1*v2[1]+...
> vc[2,*]=vc0*v1[2]+...
>
> Ciao,
> Paolo

well, there's a bit of an index mismatch
in there...

vc[0,*]=vc0*v1[0]+vc1*v2[0]+vc2*v3[0]
vc[1,*]=vc0*v1[1]+vc1*v2[1]+vc2*v3[1]
vc[2,*]=vc0*v1[2]+vc1*v2[2]+vc2*v3[2]

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[Message index]

		Accelerating a one-line program doing matrix multiplication By: Axel Martínez on Mon, 27 September 2010 02:18
		Re: Accelerating a one-line program doing matrix multiplication By: Axel Martínez on Thu, 30 September 2010 09:38
		Re: Accelerating a one-line program doing matrix multiplication By: pgrigis on Thu, 30 September 2010 08:03
		Re: Accelerating a one-line program doing matrix multiplication By: pgrigis on Thu, 30 September 2010 07:59
		Re: Accelerating a one-line program doing matrix multiplication By: Axel Martínez on Thu, 30 September 2010 04:05
		Re: Accelerating a one-line program doing matrix multiplication By: Axel Martínez on Thu, 30 September 2010 02:41
		Re: Accelerating a one-line program doing matrix multiplication By: Axel Martínez on Thu, 30 September 2010 01:39
		Re: Accelerating a one-line program doing matrix multiplication By: Karl[1] on Wed, 29 September 2010 09:57
		Re: Accelerating a one-line program doing matrix multiplication By: pgrigis on Wed, 29 September 2010 09:05
		Re: Accelerating a one-line program doing matrix multiplication By: Axel Martínez on Wed, 29 September 2010 08:55
		Re: Accelerating a one-line program doing matrix multiplication By: penteado on Wed, 29 September 2010 08:45
		Re: Accelerating a one-line program doing matrix multiplication By: pgrigis on Wed, 29 September 2010 08:34
		Re: Accelerating a one-line program doing matrix multiplication By: Axel Martínez on Wed, 29 September 2010 08:24

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