Hi again, Jay Cox <jaycox@xxxxxxxx> writes: > Clearly the gradient code could use some tuning. A linear blend > shouldn't take much more than 1/2 a second even with dithering. Could we improve this by preparing a reasonably fine array of samples and picking from these samples instead of calling gimp_gradient_get_color_at() over and over again? > The reason why the dithering case gets less of a speedup is because > the threads are fighting over the GRand state. Each thread needs to > have it's own GRand state. > > It looks like the threads are also fighting over > gradient->last_visited. My guess is that fixing this will get us > much closer to the ideal 2x speed up. I have eliminated last_visited from the gradient struct. Instead the caller of gimp_gradient_get_color_at() may now do the same optimization without any caching in the gradient itself. I very much doubt that this makes any difference though. Perhaps if you would benchmark a gradient blend with a lot of segments. But in the general case it's just a few of them, very often even only a single one. Now that this race condition is eliminated I might look into adding hooks to the pixel-processor to allow initialisation of per-thread data, like for example a GRand. Sven
