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Math Forum » Discussions » Software » comp.soft-sys.matlab

Topic: sub-pixel shifting of a matrix
Replies: 14   Last Post: Feb 7, 2013 12:23 PM

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Matt J

Posts: 4,976
Registered: 11/28/09
Re: sub-pixel shifting of a matrix
Posted: Feb 7, 2013 11:49 AM
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"Bruno Luong" <b.luong@fogale.findmycountry> wrote in message <keuml4$rtj$1@newscl01ah.mathworks.com>...
> "Matt J" wrote in message <keuln5$onb$1@newscl01ah.mathworks.com>...
>
> >
> > Maybe, but only because there are some funny sub-optimal things happening inside conv2 implementation-wise, and because the interpolation kernel here happens to be small. There's no way the 3rd version below should be the slowest.
>
> Of course. The reason is obvious: 2+2 = 2*2, but 10+10 << 10*10.
============

That doesn't explain why the 3rd version was the slowest. The 3rd version uses a 10+10 tensorial operation so since 10+10 << 10*10, you would expect the 3rd version to be faster (or comparable to) the others.

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