Date: Wed, 07 Aug 2024 10:07:32 +0200 From: Paul Zimmermann <Paul.Zimmermann@inria.fr> To: Konstantin Belousov <kostikbel@gmail.com> Cc: hackers@freebsd.org, numerics@freebsd.org Subject: Re: kargl@freebsd.org, sgk@troutmask.apl.washington.edu, vincenzo.innocente@cern.ch, riemannic@gmail.com, johnmather@sidefx.com Message-ID: <p9u04j7wah8b.fsf@coriandre.loria.fr> In-Reply-To: <ZrI5pocdm0Zbl9pW@kib.kiev.ua> (message from Konstantin Belousov on Tue, 6 Aug 2024 17:56:38 %2B0300) References: <p9u0ed713j4u.fsf@coriandre.loria.fr> <ZrI5pocdm0Zbl9pW@kib.kiev.ua>
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Hi Konstantin,
> Date: Tue, 6 Aug 2024 17:56:38 +0300
> From: Konstantin Belousov <kostikbel@gmail.com>
> Cc: hackers@freebsd.org, numerics@freebsd.org
>
> On Tue, Aug 06, 2024 at 02:56:01PM +0200, Paul Zimmermann wrote:
> > Hi,
> >
> > we have updated our comparison with FreeBSD 14.1:
> >
> > https://members.loria.fr/PZimmermann/papers/accuracy.pdf
> >
> > Remaining issues in 14.1:
> >
> > * the powl function is not thread-safe
> This is for 80-bit long double, am I right?
yes
> And it is because of the global vars passing values between functions?
>
> I tried to hack something in https://reviews.freebsd.org/D46237
thanks. I tried to apply your patch on top of openlibm-0.8.3 (after
stripping lib/msun). Part of it failed:
$ patch -p1 -i /tmp/D46237.diff
patching file ld80/e_powl.c
Hunk #1 FAILED at 23.
Hunk #2 FAILED at 42.
Hunk #3 succeeded at 85 (offset -41 lines).
Hunk #4 succeeded at 100 (offset -41 lines).
Hunk #5 succeeded at 135 (offset -41 lines).
Hunk #6 succeeded at 158 (offset -41 lines).
Hunk #7 succeeded at 189 (offset -41 lines).
$ cat ld80/e_powl.c.rej
--- ld80/e_powl.c
+++ ld80/e_powl.c
@@ -23,10 +23,10 @@
* P[0] x^n + P[1] x^(n-1) + ... + P[n]
*/
static inline long double
-__polevll(long double x, long double *PP, int n)
+__polevll(long double x, const long double *PP, int n)
{
long double y;
- long double *P;
+ const long double *P;
P = PP;
y = *P++;
@@ -42,10 +42,10 @@
* x^n + P[0] x^(n-1) + P[1] x^(n-2) + ... + P[n]
*/
static inline long double
-__p1evll(long double x, long double *PP, int n)
+__p1evll(long double x, const long double *PP, int n)
{
long double y;
- long double *P;
+ const long double *P;
P = PP;
n -= 1;
Also I git compiler warnings (maybe due to the rejected part):
ld80/e_powl.c: In function ‘powl’:
ld80/e_powl.c:374:29: warning: passing argument 2 of ‘__polevll’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
374 | w = x * ( z * __polevll( x, P, 3 ) / __p1evll( x, Q, 3 ) );
| ^
Apart from that, various tests I did seem to indicate the multi-thread issue
has gone, thanks!
Paul
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