On 06/02/2014 05:07 AM, Julien Cristau wrote:
For a lot of scientific packages, the upstream authors don't know what
they're doing. So I'm not sure that's much of an argument.
[citation needed]
Also, it's easy to just play with the -O option and see what's faster.
So IMO, it's a package
What do we lose if we follow upstream's compiler options ? As noted, the
program may fail to build on other architectures than amd64. I do not think
that the unavailability of such non-core packages on other architectures is
a problem (no user base),
No, the problem is that it would
On Mon, 02 Jun 2014, Thomas Goirand wrote:
On 06/02/2014 05:07 AM, Julien Cristau wrote:
For a lot of scientific packages, the upstream authors don't know what
they're doing. So I'm not sure that's much of an argument.
[citation needed]
Also, it's easy to just play with the -O option
On Mon, Jun 02, 2014 at 10:36:01AM -0300, Henrique de Moraes Holschuh wrote:
As long as you have a way to regression-test. And I don't mean performance
regressions, either. Although issues with -O3 are rare, they're not unheard
of.
Looking at the `man gcc' page, I fail to see, outside
On Mon, 02 Jun 2014, Xavier Roche wrote:
On Mon, Jun 02, 2014 at 10:36:01AM -0300, Henrique de Moraes Holschuh wrote:
As long as you have a way to regression-test. And I don't mean performance
regressions, either. Although issues with -O3 are rare, they're not unheard
of.
Looking at
On 01.06.2014 05:39, Steve Langasek wrote:
On Sun, Jun 01, 2014 at 12:37:18AM +0200, Tollef Fog Heen wrote:
]] Steve Langasek
FWIW, the recent port of Ubuntu to ppc64el uses -O3 as the default, because
IBM has broad experience in resolving performance issues for their own
hardware and have
* Julian Taylor jtaylor.deb...@googlemail.com [140601 14:29]:
I would not go into detail about O2 or O3 in the policy.
The meaning of these flags is very compiler specific. E.g. clang will
enable vectorization already at O2 and adds almost no extra passes with O3.
I think it would be better
On Fri, May 30, 2014 at 07:21:08 +0900, Charles Plessy wrote:
Perhaps we can stop overriding this option ? For a lot of scientific
packages, -O3 is chosen by the upstream author, and I always feel bad
that if we make the programs slower by overriding it to -O2, it will
reflect poorly on
Le Sun, Jun 01, 2014 at 11:07:32PM +0200, Julien Cristau a écrit :
On Fri, May 30, 2014 at 07:21:08 +0900, Charles Plessy wrote:
Perhaps we can stop overriding this option ? For a lot of scientific
packages, -O3 is chosen by the upstream author, and I always feel bad
that if we make the
Charles Plessy ple...@debian.org schrieb:
Perhaps we can stop overriding this option ? For a lot of scientific
packages, -O3 is chosen by the upstream author, and I always feel bad
that if we make the programs slower by overriding it to -O2, it will
reflect poorly on Debian as a distribution
]] Steve Langasek
FWIW, the recent port of Ubuntu to ppc64el uses -O3 as the default, because
IBM has broad experience in resolving performance issues for their own
hardware and have found that -O3 gives an overall better experience for
their customers. It will be difficult for Debian to
On Sun, 01 Jun 2014, Tollef Fog Heen wrote:
FWIW, the recent port of Ubuntu to ppc64el uses -O3 as the default, because
IBM has broad experience in resolving performance issues for their own
hardware and have found that -O3 gives an overall better experience for
their customers. It will
On Sun, Jun 01, 2014 at 12:37:18AM +0200, Tollef Fog Heen wrote:
]] Steve Langasek
FWIW, the recent port of Ubuntu to ppc64el uses -O3 as the default, because
IBM has broad experience in resolving performance issues for their own
hardware and have found that -O3 gives an overall better
On Fri, May 30, 2014 at 07:36:24AM +0900, Mike Hommey wrote:
On Thu, May 29, 2014 at 12:21:06PM -0700, Russ Allbery wrote:
Xavier Roche xav...@debian.org writes:
I have a rather silly question: most (all ?) packages are built by
default with -02 - something which is inherited from
On Fri, May 30, 2014 at 11:10:29AM +1000, Russell Stuart wrote:
In particular -O3 turns on auto-vectorisation. It can provide a big
speed up to programs that can take advantage of it
[...]
As others have pointed our -O3 turns on optimisations that help on some
architectures and hinder on
Bottom line: the vectorisation provided -O3 can provide big speed ups to
some scientific programs, but it is ineffective on Debian because by
necessity it tells gcc to compile code for lowest common denominator CPU
which doesn't have the necessary instructions.
Ineffective on i386, but amd64
On 30.05.2014 09:40, Xavier Roche wrote:
On Fri, May 30, 2014 at 11:10:29AM +1000, Russell Stuart wrote:
In particular -O3 turns on auto-vectorisation. It can provide a big
speed up to programs that can take advantage of it
[...]
As others have pointed our -O3 turns on optimisations that
CP == Charles Plessy ple...@debian.org writes:
CP Perhaps we can stop overriding this option ? For a lot of scientific
CP packages, -O3 is chosen by the upstream author, and I always feel bad
CP that if we make the programs slower by overriding it to -O2, it will
CP reflect poorly on Debian as
SL == Steve Langasek vor...@debian.org writes:
SL The current default of -O2 is based on the fact that adding -O3 may give
SL worse results than -O2.
On x86_64 I've yet to find anything which is slow enough to notice where
moving to O3 helped.
The memory pressure from the larger code segments
Hi folks,
I have a rather silly question: most (all ?) packages are built by default with
-02 - something which is inherited from autotool's '-g -O2' default flagsd, I
presume.
Is -O3 considered too dangerous ? (AFAICS, potential issues are mainly present
in O2) Or is it considered worthless
Xavier Roche xav...@debian.org writes:
I have a rather silly question: most (all ?) packages are built by
default with -02 - something which is inherited from autotool's '-g -O2'
default flagsd, I presume.
Is -O3 considered too dangerous ? (AFAICS, potential issues are mainly
present in O2)
Le Thu, May 29, 2014 at 12:21:06PM -0700, Russ Allbery a écrit :
Xavier Roche xav...@debian.org writes:
I have a rather silly question: most (all ?) packages are built by
default with -02 - something which is inherited from autotool's '-g -O2'
default flagsd, I presume.
Is -O3
On Thu, May 29, 2014 at 12:21:06PM -0700, Russ Allbery wrote:
Xavier Roche xav...@debian.org writes:
I have a rather silly question: most (all ?) packages are built by
default with -02 - something which is inherited from autotool's '-g -O2'
default flagsd, I presume.
Is -O3 considered
On Fri, 2014-05-30 at 07:21 +0900, Charles Plessy wrote:
For a lot of scientific packages, -O3 is chosen by the upstream
author, and I always feel bad that if we make the programs slower
by overriding it to -O2, it will reflect poorly on Debian as a
distribution for scientific works.
In
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