[Bug fortran/30285] New: gfortran huge (excessive?) memory usage with large modules

["anlauf at gmx dot de" <gcc-bugzilla at gcc dot gnu dot org>]

Hi,

gfortran seems to use much more memory at compile time
when I "use" larger modules that contain many symbols,
even if I "use, only" selected one.  In the described
situation it needs significantly more memory than
"competitors".

The attached archive contains the following main program
and three (3) large modules to demonstrate this.
The variant with the commented lines uncommented
goes beyond 500 MB virtual memory in a Linux/x86 machine.


program main
  use mo_psas,          only: setup_psas
  use mo_3dvar,         only: obs, bg
!  use mo_t_enkf,        only: enkf_driver  ! Uncomment to go beyond 500 MB
virt
ual mem.
  implicit none
  call setup_psas (obs% o, bg% grid% a, bg)
!  call enkf_driver
end program main

Compiling this program with:
% gfortran -S -fmem-report -ftime-report
Memory still allocated at the end of the compilation process
Size   Allocated        Used    Overhead
8           4096        2816          96 
16            16k         13k        256 
64          4096        1088          40 
128         4096         768          36 
256         4096        2304          32 
512           64k         61k        512 
2048          36k         36k        288 
4096          16k         16k        128 
8192        8192        8192          32 
32768        416k        416k        416 
8388608       8192k       8192k         32 
56          4096         280          40 
104           20k         17k        180 
92           106M        105M        958k
80          4096          80          36 
88            73M         72M        661k
24            24k         15k        312 
72          4096         288          36 
28          9208k       9189k        107k
112           44k         37k        396 
36          4096         288          44 
12         10164k      10146k        178k
40            33M         33M        364k
Total        240M        238M       2274k

String pool
entries         336041
identifiers     336041 (100.00%)
slots           524288
bytes           4934k (350k overhead)
table size      2048k
coll/search     0.6655
ins/search      0.2790
avg. entry      15.04 bytes (+/- 0.99)
longest entry   34

??? tree nodes created

(No per-node statistics)
Type hash: size 1021, 175 elements, 0.084121 collisions
DECL_DEBUG_EXPR  hash: size 1021, 0 elements, 0.000000 collisions
DECL_VALUE_EXPR  hash: size 2097143, 865473 elements, 1.209451 collisions

Execution times (seconds)
 garbage collection    :   1.56 (19%) usr   0.00 ( 0%) sys   1.54 (17%) wall    
   0 kB ( 0%) ggc
 parser                :   6.29 (78%) usr   0.78 (99%) sys   7.08 (79%) wall 
25
1744 kB (100%) ggc
 symout                :   0.00 ( 0%) usr   0.00 ( 0%) sys   0.01 ( 0%) wall    
   0 kB ( 0%) ggc
 TOTAL                 :   8.11             0.79             8.91            
25
2445 kB
Extra diagnostic checks enabled; compiler may run slowly.
Configure with --disable-checking to disable checks.


The modules are extracted from a larger project and should
be sufficient to just compile the example.  The project
uses MPI (mpich) which is why these symbols occur quite
frequently in the module files.  Gfortran seems to handle
the present case quite inefficiently.  Maybe there is a
solution that handles used modules more economically...

Cheers,
-ha


-- 
           Summary: gfortran huge (excessive?) memory usage with large
                    modules
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: anlauf at gmx dot de
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30285