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On Thu, Aug 17, 2006 at 07:55:33AM +0200, Jonas Lindqvist wrote:
> Hi!
>
> I feel an urge to ask some questions... (Perhaps silly, but anyway...
> I know I could probably find the answers by digging in the code a bit
> deeper, but I admit I'm lazy...)
>
> * The function gabor_filter, in gabor.c, now uses a fixed array of
> 65536 doubles, instead of callocing the size indicated by the width
> and height that are passed as parameters to gabor_filter(...). Very
> well...
> Are the width and height always 256, or can they be 128*512 or
> 2*32768 or whatever?
>
the perl script that imports our images re-sizes everything to 256x256.
> * I guess that most modern CPUs have some kind of SSE2-ish features
> that gcc could use, but what would the effect of the patch be for an
> architecture that lacks it? (Something seriously old, pre MMX, or
> something else that perhaps one would not use for this application
> anyway...)
GCC's autovec extentions are also written to take advantage of altivec,
on the newer powerPC mac hardware.. AND splitting it up like this
still makes things run faster on earlier processors.
>
> * Wouldn't memset be faster than looping and setting to zero?:
> for (i = 0; i < width*height; i++)
> {
> conv[i]= 0; /* needs to be zeroed */
> }
> and isn't width*height always 65536?
possibly. i'll look into memseting. ;)
Julia Longtin <[email protected]>
>
> /Jonas
>
>
>
>
>
> >Yet another patch..
> >
> >This one is a case of "add code to gain speed".
> >
> >By adding a special case handling of "kernel being tested
> >is within the borders of the image",you gain speed by not
> >performing a conditional in the loop, which allows for
> >gcc 4.1's autovec engine to change your loop to a series
> >of SSE2 instructions.
> >
> >Get all that? :)
> >
> >Anyways, this brings the speed down to ~1.3 on my machine.
> >
> >the 70-* and 80-* patches have equivilents for convolutions
> >two and four, i'm just not getting it quite right yet...
> >
> >I'm also attaching my testing program, so that others can
> >check my work.
> >
> >Julia Longtin <[email protected]>
> ><80-ChangeLog>
> ><80-FeatureExtraction_gabor.c_move_conditional_and_parallelize.patch>
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