There is less calculation, but the noise matrix takes up cache space (about half a modern CPU's L1) and hence increases memory pressure. The actual performance relationship is probably hardware dependent, but on my laptop doing a quick check with patched lowlevel-blt-bench:
- Bayer is ~8% faster than blue noise - Bayer is only ~5% faster if I use `dither_blue_noise_64x64[((y & 0x3f) << 6) | (x & 0x3f)]` in the index computation, which I would have expected GCC to do automatically but oh well. - Both are about the same speed with uint16_t array for the blue noise (halves memory consumption). I will make those two changes (they are clearly desirable) and re-post the blue noise patch. Since this is in a write-back loop which should be memory-bound in general, I think it makes sense to keep Bayer as FAST dithering -- but I'm not opposed to removing it. - Basile On 4/22/19 8:12 PM, Bill Spitzak wrote: > Is the "blue noise" version actually slower than the Bayer? Seems to > be doing a bit less calculation but it reading the array of weights. > The removal of the need for the pattern offset seems like a win. > > On Mon, Apr 22, 2019 at 9:27 AM Matt Turner <matts...@gmail.com > <mailto:matts...@gmail.com>> wrote: > > On Fri, Apr 19, 2019 at 4:52 PM Bryce Harrington > <br...@bryceharrington.org <mailto:br...@bryceharrington.org>> wrote: > > Inkscape would love to see Basile's dithering patches included. Our > > testing shows that they make a huge quality difference for our > users; > > this solves a critical need. > > > > Mc and I have done some preliminary investigation into how to > plumb this > > into Cairo, and would love to hear your review of Basile's > approach to > > the problem. > > I don't feel like I'm experienced enough with that side of pixman to > offer meaningful comments. I've Cc'd Søren in the hopes that he > remains interested enough in the project to review the patches that > Basile says implement the approach Søren described. > _______________________________________________ > Pixman mailing list > Pixman@lists.freedesktop.org <mailto:Pixman@lists.freedesktop.org> > https://lists.freedesktop.org/mailman/listinfo/pixman > > > _______________________________________________ > Pixman mailing list > Pixman@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/pixman
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