public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "Joost.VandeVondele at pci dot uzh.ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libfortran/50673] New: very slow I/O with trailing spaces
Date: Sun, 09 Oct 2011 11:04:00 -0000	[thread overview]
Message-ID: <bug-50673-4@http.gcc.gnu.org/bugzilla/> (raw)

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50673

             Bug #: 50673
           Summary: very slow I/O with trailing spaces
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: Joost.VandeVondele@pci.uzh.ch


The following testcase (derived from CP2K, which required 20min to read a 600Mb
file) is about 100x times slower with gfortran than with ifort (12.0.4)

CHARACTER(LEN=40480) :: line="O 0.12456789 0.123456789 0.123456789"
CHARACTER(LEN=2) :: AA
REAL*8 :: vec(3)
DO i=1,10000
   read(line,*) AA,vec
ENDDO
END

The issue seems related to how efficient the trailing spaces are handled in
both compilers. 4.7 is a bit (20%) slower than 4.3, but nothing fundamental.

Profiling the code shows that most time is spent in next_char, mem_read,
memcpy, eat_spaces.


             reply	other threads:[~2011-10-09 11:04 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-10-09 11:04 Joost.VandeVondele at pci dot uzh.ch [this message]
2011-10-09 12:05 ` [Bug libfortran/50673] " Joost.VandeVondele at pci dot uzh.ch
2012-04-15 11:54 ` tkoenig at gcc dot gnu.org
2012-04-15 11:57 ` tkoenig at gcc dot gnu.org
2012-04-17 19:34 ` burnus at gcc dot gnu.org

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=bug-50673-4@http.gcc.gnu.org/bugzilla/ \
    --to=gcc-bugzilla@gcc.gnu.org \
    --cc=gcc-bugs@gcc.gnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
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 read-only IMAP folder(s) and NNTP newsgroup(s).