[Bug libfortran/16339] Unformatted i/o on large arrays inefficient
--- Comment #8 from fxcoudert at gcc dot gnu dot org 2005-12-09 09:24 --- *** Bug 21820 has been marked as a duplicate of this bug. *** -- fxcoudert at gcc dot gnu dot org changed: What|Removed |Added CC||kargl at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16339
[Bug libfortran/16339] Unformatted i/o on large arrays inefficient
--- Comment #7 from fxcoudert at gcc dot gnu dot org 2005-11-04 19:50 --- With array size=2000, timings are: g77: 2.30 s gfortran-4.0 (without commited patch): 17.0 gfortran-mainline: 2.66 s intel: 3.15 s I think we can close this PR. -- fxcoudert at gcc dot gnu dot org changed: What|Removed |Added CC||fxcoudert at gcc dot gnu dot ||org Status|NEW |RESOLVED Known to fail||4.0.2 Known to work||4.1.0 Resolution||FIXED Target Milestone|--- |4.1.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16339
[Bug libfortran/16339] Unformatted i/o on large arrays inefficient
--- Comment #6 from cvs-commit at gcc dot gnu dot org 2005-10-07 20:02 --- Subject: Bug 16339 CVSROOT:/cvs/gcc Module name:gcc Changes by: [EMAIL PROTECTED] 2005-10-07 20:02:28 Modified files: libgfortran: ChangeLog libgfortran/io : io.h unix.c transfer.c Log message: 2005-10-07 Janne Blomqvist <[EMAIL PROTECTED]> PR fortran/16339 PR fortran/23363 * io/io.h: Add read and write members to stream, define access macros. * io/transfer.c (read_block_direct): New function. (write_block_direct): New function. (unformatted_read): Change to use read_block_direct. (unformatted_write): Change to use write_block_direct. * io/unix.c: Remove mmap includes and defines. (writen): Remove. (readn): Remove. (reset_stream): New function. (do_read): New function. (do_write): New function. (fd_flush): Change to use do_write() instead of writen(). (fd_alloc_r_at): Change to use do_read(). (fd_seek): Change return type to try, as the prototype. Add check to avoid syscall overhead if possible. (fd_read): New function. (fd_write): New function. (fd_open): Set pointers for new functions. (mem_read): New function. (mem_write): New function. (open_internal): Set pointers for new functions. (is_seekable): Clean up comment. Patches: http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/ChangeLog.diff?cvsroot=gcc&r1=1.319&r2=1.320 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/io/io.h.diff?cvsroot=gcc&r1=1.32&r2=1.33 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/io/unix.c.diff?cvsroot=gcc&r1=1.42&r2=1.43 http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libgfortran/io/transfer.c.diff?cvsroot=gcc&r1=1.62&r2=1.63 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16339
[Bug libfortran/16339] Unformatted i/o on large arrays inefficient
--- Additional Comments From jblomqvi at cc dot hut dot fi 2005-06-05 21:19 --- Some further thoughts on this issue: http://gcc.gnu.org/ml/fortran/2005-06/msg00084.html -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16339
[Bug libfortran/16339] Unformatted i/o on large arrays inefficient
--- Additional Comments From jblomqvi at cc dot hut dot fi 2005-06-04 17:50 --- It seems that with current mainline, while gfortran still loses to g77 and ifort, the difference isn't that large. Executing via strace shows that writes are nowadays done in 8k blocks, which probably explains the change. Here are the total times (removing the output file between each invocation): ifort 8.0: 0,109 g77 3.3: 1,349 gfortran 4.1 20050604: 1,458 Blocksizes in bytes are: ifort 8.0: 262144 g77 3.3: 4096 gfortran 4.1 20050604: 8192 Gfortran is the only one which uses mmap. Also, we can see that ifort uses a _huge_ blocksize, which probably explains why it's over 10 times faster. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16339
[Bug libfortran/16339] Unformatted i/o on large arrays inefficient
--- Additional Comments From Thomas dot Koenig at online dot de 2005-03-04 10:47 --- This is really _very_ inefficient, by a factor of 20. Some test numbers: $ g77 write-record.f $ time ./a.out real0m1.819s user0m1.774s sys 0m0.044s $ gfortran write-record.f $ time ./a.out real0m43.723s user0m9.003s sys 0m34.571s $ cat write-record.f program main integer n parameter (n=1000) real a(n) write (10) (a(i),i=1,n) end $ gfortran -v Using built-in specs. Target: ia64-unknown-linux-gnu Configured with: ../gcc-4.1-20050227/configure --prefix=/home/zfkts --enable-languages=c,f95 Thread model: posix gcc version 4.1.0 20050227 (experimental) By comparison: $ ifort write-record.f $ time ./a.out real0m0.117s user0m0.001s sys 0m0.116s -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16339
