[petsc-users] Problems with the intel compilers

Sean Dettrick sdettrick at gmail.com
Tue Oct 27 18:22:52 CDT 2009

Intel optimization is slow, and is turned on by default.  If you turn  
off intel optimization completely with -O0, then you'll probably find  
compilation speeds up to be similar to gnu.

Is the increased compilation time of intel worth it?  We find intel  
programs are usually faster than gnu ones.  And the intel debugger idb  
is in many ways more powerful than gdb.  But on the other hand we have  
a fortran based CG solver where gfortran compiled code is much faster  
than the intel one.


On Oct 27, 2009, at 3:54 PM, Dominik Szczerba wrote:

> Thanks Ando, I know of the slight speed advantage in some cases on  
> the Intel side, but the question was more why the compilation takes  
> so much longer?
> Dominik
> Andreas Grassl wrote:
>> Hi Dominik,
>> Dominik Szczerba wrote:
>>> I have noticed already a longer while ago: setting up PETSc with the
>>> Intel compilers (--with-cc=icc --with-cxx=icpc) takes an order of
>>> magnitude longer than with the native GNU. The step taking most of  
>>> the
>>> time is configuring mpich. I have tried to configure mpich  
>>> separately
>>> and indeed, with gnu it is a breeze, with intel 10x slower. In both
>>> cases, linux both 32 and 64 bit, Ubuntu 9.04 and debian testing.  
>>> Intel
>>> compilers 10.x and 11.x.
>>> I just wanted to ask opinion if anybody has similar observations  
>>> and/or
>>> finds using intel worthwhile at all.
>> On itanium machines intel compilers produce much faster code  
>> compared to
>> gnu-compilers. On other machines I did not notice a big speed  
>> difference, but I
>> think intel compilers produce slightly faster code as well.
>> Cheers,
>> ando

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