From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 122E0383F40B; Thu,  3 Jun 2021 08:21:28 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 122E0383F40B
From: "nadavhalahmi560 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/100855] pow run time gfortran vs ifort
Date: Thu, 03 Jun 2021 08:21:26 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: fortran
X-Bugzilla-Version: 11.1.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: nadavhalahmi560 at gmail dot com
X-Bugzilla-Status: WAITING
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P4
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-100855-4-RKt0RWzMaG@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-100855-4@http.gcc.gnu.org/bugzilla/>
References: <bug-100855-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Thu, 03 Jun 2021 08:21:28 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100855

--- Comment #7 from Nadav Halahmi <nadavhalahmi560 at gmail dot com> ---
(In reply to Dominique d'Humieres from comment #6)
> On a MacOS, Corei9, 2.4Ghz, the program runs in ~1s, almost indpendtly of
> the option level.
>=20
> This PR remind me an old problem in which the transcendental functions we=
re
> almost slower for REAL(4) then for REAL(8) on some Unix distros (Fedora(?=
),
> based of "correct rounding").
>=20
> What are your timings if you replace
>=20
>     real :: sum, n, q
>=20
> with
>=20
>     real(8) :: sum, n, q
>=20
> and
>=20
>             sum =3D sum + (i ** (0.05 + n))
>=20
> with
>=20
>             sum =3D sum + (i ** (0.05_8 + n))
>=20
> ?

Timings for this change (notice the result was also changed):
gnu:
   150945570.07620683=20=20=20=20=20
Time =3D  6.303 seconds.
intel:
   150945570.076207=20=20=20=20=20
Time =3D  2.349 seconds.

So gnu is indeed faster for real(8), but the result was changed.=