"Juan A. Suarez Romero" <jasua...@igalia.com> writes: > On Tue, 2017-01-17 at 11:34 +0100, Juan A. Suarez Romero wrote: >> > The above does not necessarily sum to "we shouldn't fix it" but it >> > probably does mean it's low-priority at best and we need to be careful. >> > >> > Looking a bit into the math of atan2, I'm not convinced flushing denorms >> > to zero is actually what we want to do. For x, I think it's valid, but as >> > y approaches 0, you get +/- pi/2 depending on whether y positive or >> > negative. As both approach zero, it's undefined. As you approach >> > infinity, it approaches something in the interval [-pi/2, pi/2] but it >> > depends on the direction of approach. If you do "man atan2" you'll see >> > this all layed out in a horrifying amount of detail (somewhere around a >> > dozen different cases). >> > >> > >> >> Yes, originally I only flushed 'x'. But then also flushed 'y' to keep >> coherence. But didn't think about that corner case you mention. I think we >> can remove the flush to 0 in 'y'. > > Actually, after doing a couple of tests more, I don't think we need to flush > 'x' any more. > > The thing is that originally I added the flush to 0 to solve a couple of > cases from Vulkan CTS atan2 tests. But later I modified the code to cope with > infinities, which lead a refactoring of code. I think this refactoring made > the flush to 0 not required any more. > > I've run the tests again getting rid of both flushes, and seems results are > exactly the same as with the flush. So maybe they are not required after all. >
So what exactly from the many checks you added makes the tests pass? IOW, what property do the vulkan CTS tests take for granted that the current atan2 implementation doesn't fulfill? > > J.A. > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
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