Can be a subroutine slower when is placed in a module?

[Jorge D'Elia]

Hi folks,

I'm using the experimental version GNU Fortran (GCC) 6.0.0 20151107 
(soon I will build the last experimental version!), on a 
x86_64 machine (i7-3930K, 3.20GHz) with:

 Linux version 4.2.3-200.fc22.x86_64 
 (mockbuild@bkernel01.phx2.fedoraproject.org) 
 (gcc version 5.1.1 20150618 (Red Hat 5.1.1-4) 
 (LE)) # 1 SMP Thu 8 October 03: 2015 23:55 UTC.

Question: is expected that the computational time increases fairly 
when the task routines are placed in a module? e.g. in simple LU 
tests using one core (please, see attached tgz file):

$ test1.exe # simple LU test without a "module" o "includes"
  size;             nn =         1000
  elapsed time; tdelta =   0.16185099999999999     
  Mflops (dp) ; Mflops =    4131.3718584788885     

$ test2.exe # simple LU test using "includes"
  size;             nn =         1000
  elapsed time; tdelta =   0.16450000000000001     
  Mflops (dp) ; Mflops =    4064.8429584599794     

$ test3.exe # simple LU test using a "module"
  size;             nn =         1000
  elapsed time; tdelta =   0.27818599999999999     
  Mflops (dp) ; Mflops =    2403.6675701389236
  
from these values, e.g.

octave:1> ratio_31 = 0.27818599999999999/0.16185099999999999
ratio_31 =  1.7188
octave:2> ratio_21 = 0.16450000000000001/ 0.16185099999999999
ratio_21 =  1.0164

Thus, the CPU time using the single test1 is comparable 
with the obtained with test2 that uses "includes".  

However, the CPU time increased by 170%, more or less, in 
the test3 where a module is used. Question: it is expected 
behavior, or there's something that I missing? e.g. in the 
GFortran compilation flags, or in the coding style used? etc.


Thanks in advance.
Jorge.
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