[Users] problem with ifort 10 compiler

[Erik Schnetter]

On Jan 16, 2008, at 06:26:26, Christian Reisswig wrote:

> Hi,
>
> when I try to compile Cactus, I get problems compiling Fortran  
> code, since
> Cactus sets an optimization option "-xN".
> This option doesn't seem to be supported by the Intel Fortran 10  
> compiler.
>
> ifort -help reveals:
>
> v10:
>
> -x<codes>  generate specialized code to run exclusively on processors
>            indicated by <codes> as described below
>     W  Intel Pentium 4 and compatible Intel processors
>     P  Intel(R) Core(TM) Duo processors, Intel(R) Core(TM) Solo  
> processors,
>        Intel Pentium 4 and compatible Intel(R) processors with  
> Streaming
>        SIMD Extensions 3 (SSE3) instruction support
>     T  Intel(R) Core(TM)2 Duo processors, Intel(R) Core(TM)2 Quad
>        processors, and Intel(R) Xeon(R) processors with SSSE3
>     O  Intel(R) Core(TM)2 Duo processors.  Code is expected to run  
> properly
>        on any processor that supports SSE3, SSE2 and SSE  
> instruction sets
>
>
> <v10:
>
>     K  Intel Pentium III and compatible Intel processors
>     W  Intel Pentium 4 and compatible Intel processors
>     N  Intel Pentium 4 and compatible Intel processors.  Enables new
>        optimizations in addition to Intel processor-specific  
> optimizations
>     P  Intel Core(TM) Duo processors, Intel Core(TM) Solo  
> processors, Intel
>        Pentium 4 and compatible Intel processors with Streaming SIMD
>        Extensions 3 (SSE3) instruction support
>     B  Intel Pentium M and compatible Intel processors
> -x<codes>  generate specialized code to run exclusively on processors
>            indicated by <codes> as described above.
>
>
> So I guess the -xN option has to be replaced by -xW.


I think the option should be omitted.  Which of these options should  
be used depends on the system; Cactus should either autoconfigure the  
system and optimise for the system where it is compiled, or should  
(by default) produce binaries which run everywhere.  -xW seems to  
break for Pentium III systems -- I don't think they are in widespread  
use, but you never know.

We could use -axP, which generates code that runs everywhere but is  
optimised for modern machines.  For example, -fast also implies -xP.

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>   http://www.cct.lsu.edu/ 
~eschnett/

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