Re: Speed comparison with Intel compiler

[Ron Young <ronyoung8 at verizon dot net>]

Ignacio Fernández Galván wrote:
> Hi all,
>
> I just tried running a piece of code I'm writing compiled with gfortran
> and with ifort, and the difference is worrying.
>
> ifort: 23 s
> gfortran: 165 s
> gfortran -O3 -ffast-math -funroll-loops -ftree-vectorize
> -march=athlon-xp -msse -mfpmath=sse,387: 164 s
>
> The code has nothing really special, it just converts some coordinates
> and quaternions into transformed coordinates, and the main part I guess
> is generating the rotation matrices and applying them (with MATMUL).
> There is also some (maybe too much) disk I/O)
>
> Is there some known defficiency of gfortran here? Is it worth to
> investigate this more in depth? How could I (easily) tell what is
> taking so long time (I guess I could try to prepare some simpler
> program which shows the same effect)?
>
> Thanks
> Ignacio
>
> P.S. gfortran is (gcc version 4.3.0 20070402), ifort is (Version 9.1).
>
>
> 	
> 	
> 		
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>   
I find it easier to use oprofile

[root@myhost quaternions]# opcontrol --no-vmlinux
[root@myhost quaternions]# gfc -o test -O3 -march=core2 -msse2 
-mfpmath=sse -ffast-math test.f90
[root@myhost quaternions]# opcontrol --reset ; opcontrol --image=./test 
--start ; ./test ; opcontrol --stop
Signalling daemon... done
Profiler running.
Stopping profiling.
[root@myhost quaternions]# opreport  -c -% -t .5 test
CPU: Core 2, speed 1663.27 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a 
unit mask of 0x00 (Unhalted core cycles) count 100000
samples  %        symbol name
-------------------------------------------------------------------------------
1008251  50.3400  mem_alloc_r_at
 1008251  50.3400  mem_alloc_r_at [self]
-------------------------------------------------------------------------------
481072   24.0190  next_char
 481072   24.0190  next_char [self]
-------------------------------------------------------------------------------
170937    8.5346  _gfortrani_is_array_io
 170937    8.5346  _gfortrani_is_array_io [self]
-------------------------------------------------------------------------------
128609    6.4212  _gfortrani_is_stream_io
 128609    6.4212  _gfortrani_is_stream_io [self]
-------------------------------------------------------------------------------
89973     4.4922  _gfortrani_is_internal_unit
 89973     4.4922  _gfortrani_is_internal_unit [self]
-------------------------------------------------------------------------------
26723     1.3342  eat_spaces
 26723     1.3342  eat_spaces [self]
-------------------------------------------------------------------------------
10902     0.5443  ____strtod_l_internal
 10902     0.5443  ____strtod_l_internal [self]
-------------------------------------------------------------------------------
[root@myhost quaternions]#