[Bug libfortran/50673] New: very slow I/O with trailing spaces

[Bug libfortran/50673] New: very slow I/O with trailing spaces

[Joost.VandeVondele at pci dot uzh.ch]

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.

[Bug libfortran/50673] very slow I/O with trailing spaces

[Joost.VandeVondele at pci dot uzh.ch]

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

--- Comment #1 from Joost VandeVondele <Joost.VandeVondele at pci dot uzh.ch> 2011-10-09 12:04:55 UTC ---
Actually, since eating the trailing spaces is the issue (seems to be
implemented very generally in libfortran), the following is a practical
workaround in this case:

read(line(1:LEN_TRIM(line)),*) AA,vec

maybe something along these lines could be done in the runtime ?

[Bug libfortran/50673] very slow I/O with trailing spaces

[tkoenig at gcc dot gnu.org]

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

Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED
         AssignedTo|unassigned at gcc dot       |tkoenig at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #3 from Thomas Koenig <tkoenig at gcc dot gnu.org> 2012-04-15 11:53:44 UTC ---
Fixed on trunk, closing.

[Bug libfortran/50673] very slow I/O with trailing spaces

[tkoenig at gcc dot gnu.org]

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

--- Comment #2 from Thomas Koenig <tkoenig at gcc dot gnu.org> 2012-04-15 11:52:49 UTC ---
Author: tkoenig
Date: Sun Apr 15 11:52:44 2012
New Revision: 186466

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186466
Log:
2012-04-15  Thomas Koenig  <tkoenig@gcc.gnu.org>

    PR libfortran/38199
    PR libfortran/50673
    * intrinsics/string_intriniscs_inc.c (string_len_trim):
    Remove prototypes for string_len_trim and move to...
    * libgfortran.h (string_len_trim): ... here and
    (string_len_trim_char4): ...here.
    * io/unit.c: For non-array internal arrays where we do reading,
    adjust the record length to the last non-blank character.
    * io/unix.c:  Fix typo.


Modified:
    trunk/libgfortran/ChangeLog
    trunk/libgfortran/intrinsics/string_intrinsics_inc.c
    trunk/libgfortran/io/unit.c
    trunk/libgfortran/io/unix.c
    trunk/libgfortran/libgfortran.h

[Bug libfortran/50673] very slow I/O with trailing spaces

[burnus at gcc dot gnu.org]

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

--- Comment #4 from Tobias Burnus <burnus at gcc dot gnu.org> 2012-04-17 19:30:38 UTC ---
Author: burnus
Date: Tue Apr 17 19:30:29 2012
New Revision: 186548

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186548
Log:
2012-04-17  Tobias Burnus  <burnus@net-b.de>

        PR libfortran/38199
        PR libfortran/50673
        * io/unit.c (get_internal_unit): Properly check for the presence
        of the format string.


Modified:
    trunk/libgfortran/ChangeLog
    trunk/libgfortran/io/unit.c