<html><head></head><body><div>On Tue, 2017-01-17 at 11:34 +0100, Juan A. Suarez Romero wrote:</div><blockquote type="cite"><div><br></div><blockquote type="cite"><div dir="ltr"><div>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.<br><br></div><div>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).<br></div></div><div class="gmail_extra"><br></div></blockquote><div><br></div><div>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'.</div><div></div></blockquote><div><br></div><div>Actually, after doing a couple of tests more, I don't think we need to flush 'x' any more.</div><div><br></div><div>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.</div><div><br></div><div>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.</div><div><br></div><div><br></div><div> J.A.</div><div><br></div></body></html>