mailing list of musl libc
 help / color / mirror / code / Atom feed
* math/powf regression on d28cd0ad commit
@ 2019-12-04  2:10 Ruinland ChuanTzu Tsai
  2019-12-04  9:33 ` Szabolcs Nagy
  0 siblings, 1 reply; 2+ messages in thread
From: Ruinland ChuanTzu Tsai @ 2019-12-04  2:10 UTC (permalink / raw)
  To: musl; +Cc: alankao

Hi musl fellows,
sorry for making the noise again.

Yet I encountered a regression of libc-test's math/powf on x86_64 and
RV64 during the transitions from v1.1.22 to v1.1.23. After bisecting, I
managed to locate the commit that breaks powf() test to be d28cd0ad ,
which introduces a new implementation of powf().

Fail log is shown as follow :

src/math/ucb/powf.h:103: bad fp exception: RU powf(0x1.fffffep+127,0x1p+0)=0x1.fffffep+127, want 0 got INEXACT|OVERFLOW 
X src/math/ucb/powf.h:530: bad fp exception: RN powf(0x1.fffff8p-127,0x1p+0)=0x1.fffff8p-127, want 0 got INEXACT|UNDERFLOW
X src/math/ucb/powf.h:533: bad fp exception: RN powf(0x1.fffffcp-127,0x1p+0)=0x1.fffffcp-127, want 0 got INEXACT|UNDERFLOW
X src/math/ucb/powf.h:719: bad fp exception: RN powf(-0x1.fffff8p-127,0x1p+0)=-0x1.fffff8p-127, want 0 got INEXACT|UNDERFLOW
X src/math/ucb/powf.h:722: bad fp exception: RN powf(-0x1.fffffcp-127,0x1p+0)=-0x1.fffffcp-127, want 0 got INEXACT|UNDERFLOW
FAIL ./src/math/powf.exe [status 1]

I took a quick investigation on the RU powf(0x1.fffffep+127,0x1p+0).
In the very end of powf() , a "y", which is a little bit larger than the
expected outcome, gets passed to eval_as_float(). Since we're rounding-
up, it will become an INF, causing the testcase to fail.

It makes me wonder whether the old implementation is safe enough for
someone to revert this change by her/his own ? ( I reverted the change
for testing. It seems to be side-effect free ? )

Best regards,
Ruinland


^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, other threads:[~2019-12-04  9:33 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-12-04  2:10 math/powf regression on d28cd0ad commit Ruinland ChuanTzu Tsai
2019-12-04  9:33 ` Szabolcs Nagy

Code repositories for project(s) associated with this public inbox

	https://git.vuxu.org/mirror/musl/

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).