Bug 726909

Summary:

Quadruple precision broken on i686

Product:

[Fedora] Fedora

Reporter:

Susi Lehtola <susi.lehtola>

Component:

gcc

Assignee:

Jakub Jelinek <jakub>

Status:

CLOSED ERRATA

QA Contact:

Fedora Extras Quality Assurance <extras-qa>

Severity:

unspecified

Docs Contact:

Priority:

unspecified

Version:

CC:

jakub

Target Milestone:

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Target Release:

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Hardware:

i686

OS:

Unspecified

Whiteboard:

Fixed In Version:

gcc-4.6.1-7.fc16

Doc Type:

Bug Fix

Doc Text:

Story Points:

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Clone Of:

Environment:

Last Closed:

2011-08-22 15:27:17 UTC

Type:

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Regression:

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Mount Type:

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Documentation:

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CRM:

Verified Versions:

Category:

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oVirt Team:

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RHEL 7.3 requirements from Atomic Host:

Cloudforms Team:

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Target Upstream Version:

Attachments:

Description	Flags
Test program	none

Description Susi Lehtola 2011-07-30 18:49:06 UTC

Created attachment 515984 [details]
Test program

There is something wrong with quadruple precision on i686, the results are rounded to double precision. This was picked up in fftw
http://koji.fedoraproject.org/koji/taskinfo?taskID=3240201

A test program, compliments of fftw upstream is attached.

$ gcc -m64 quadtest.c -lquadmath
$ ./a.out 
        6.28318530717958647692528676655900559495813619627459
        3.00000000000000000000000000000000000000000000000000
        2.00000000000000000000000000000000000000000000000000
        4.18879020478639098461685784437267065342941671581451
       -0.49999999999999999999999999999999980740700556127641
       -0.50000000000000000000000000000000000000000000000000
       -0.86602540378443864676372317075293625737304587806740
        0.86602540378443864676372317075293616107654865870560

round-off error here                       ^

$ gcc -m32 quadtest.c -lquadmath
$ ./a.out 
        6.28318530717958647692528676655900559495813619627459
        3.00000000000000000000000000000000000000000000000000
        2.00000000000000000000000000000000000000000000000000
        4.18879020478639098461685784437267065342941671581451
       -0.50000000000000004643091056722032931785465127180831
       -0.50000000000000000000000000000000000000000000000000
       -0.86602540378443861995682445604883787468431152485478
        0.86602540378443864676372317075293616107654865870560

round-off here            ^

Comment 1 Jakub Jelinek 2011-08-01 09:21:13 UTC

Excess precision issues :(
Fixed upstream so far:
http://gcc.gnu.org/ml/gcc-patches/2011-08/msg00014.html

Comment 2 Fedora Update System 2011-08-03 09:21:59 UTC

gcc-4.6.1-6.fc16 has been submitted as an update for Fedora 16.
https://admin.fedoraproject.org/updates/gcc-4.6.1-6.fc16

Comment 3 Susi Lehtola 2011-08-03 10:32:31 UTC

Can you fix this on Fedora 15 as well? It suffers from the same bug...

Comment 4 Jakub Jelinek 2011-08-03 10:44:00 UTC

Eventually yes, but will wait a bit to accumulate more issues, get the new OpenMP 3.1 stuff tested, etc.

Comment 5 Fedora Update System 2011-08-03 19:14:25 UTC

Package gcc-4.6.1-6.fc16:
* should fix your issue,
* was pushed to the Fedora 16 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing gcc-4.6.1-6.fc16'
as soon as you are able to.
Please go to the following url:
https://admin.fedoraproject.org/updates/gcc-4.6.1-6.fc16
then log in and leave karma (feedback).

Comment 6 Susi Lehtola 2011-08-05 08:24:40 UTC

Please push and build gcc-4.6.1-6 (or newer) on rawhide, since the current version there is 4.6.1-3.fc16...

Comment 7 Jakub Jelinek 2011-08-05 10:11:18 UTC

All that is needed is one karma from a proventester...

Comment 8 Fedora Update System 2011-08-05 20:07:29 UTC

Package gcc-4.6.1-7.fc16:
* should fix your issue,
* was pushed to the Fedora 16 testing repository,
* should be available at your local mirror within two days.
Update it with:
# su -c 'yum update --enablerepo=updates-testing gcc-4.6.1-7.fc16'
as soon as you are able to.
Please go to the following url:
https://admin.fedoraproject.org/updates/gcc-4.6.1-7.fc16
then log in and leave karma (feedback).

Comment 9 Fedora Update System 2011-08-22 15:26:53 UTC

gcc-4.6.1-7.fc16 has been pushed to the Fedora 16 stable repository.  If problems still persist, please make note of it in this bug report.