[Bug fortran/38199] missed optimization, regression: I/O performance
--- Comment #1 from jb at gcc dot gnu dot org 2008-11-20 14:04 --- I'm looking at I/O performance as part of PR 25561 (see also PR 37754, perhaps this is a dup?), but my changes are invasive enough that they are 4.5 material. Thanks for the report. -- jb at gcc dot gnu dot org changed: What|Removed |Added CC||jb at gcc dot gnu dot org Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Last reconfirmed|-00-00 00:00:00 |2008-11-20 14:04:55 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38199
[Bug fortran/38199] missed optimization, regression: I/O performance
--- Comment #2 from manfred99 at gmx dot ch 2008-11-20 14:59 --- The profiling of the second testcase gives % cumulative self self total time seconds secondscalls Ts/call Ts/call name 44.20 8.34 8.34 next_char 24.85 13.03 4.69 mem_read 17.04 16.25 3.22 memcpy 4.98 17.19 0.94 eat_spaces 4.03 17.95 0.76 _gfortrani_empty_internal_buffer 2.44 18.41 0.46 nml_query 2.09 18.80 0.40 strncasecmp_l 0.21 18.84 0.04 memset 0.05 18.85 0.01 __divti3 0.05 18.86 0.01 _gfortrani_write_block 0.05 18.87 0.01 next_char 0.00 18.87 0.001 0.00 0.00 MAIN__ It seems gfortran reads character by character and does not take any opportunities to shortcut the read process. For this case, one could imagine that the read routine would scan for the last non-blank character and would stop reading at this position. Perhaps ifort is doing exactly this. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38199
