[gmx-users] no altivec support found when compiling on macosx G5 gcc 3.3

[Pim Schravendijk]

Hi list,

I'm compiling gromacs 3.2.1 on macosx on a G5 and get a warning:

WARNING: no altivec support found - On G4 and later Motorola PowerPC CPUs
you can get a HUGE performance gain by using an altivec-enabled compiler.
Download the latest devtools from Apple, or gcc-3.1 from ftp.gnu.org

Since I'm using gcc 3.3, "upgrading" to 3.1 seems not logical. I have 
-fast as CFLAGS option and used ./configure without any options except 
the --prefix= option. 

Now I'd of course like to have this "HUGE performance gain" so I am 
wondering how I could get this option to work. Any ideas?

Greetings, Pim

version numbers:
Darwin Kernel Version 7.3.0: Fri Mar  5 14:22:55 PST 2004;
gcc version 3.3 20030304 (Apple Computer, Inc. build 1495)

complete warning message:
configure:5013: checking whether gcc accepts -faltivec
configure:5031: result: yes
configure:5087: checking whether gcc accepts -funroll-all-loops
configure:5105: result: yes
configure:5118: checking whether gcc accepts -mcpu=7450
configure:5136: result: yes
configure:5148: checking whether gcc accepts -mtune=970
configure:5166: result: yes
configure:5481: checking whether the compiler supports altivec extensions
configure:5510: gcc -c -fast 
-I/people/thnfs/homes/schraven/bin/fftwmacsingle/include/ conftest.c >&
5
configure: In function `main':
configure:5509: error: `choke_me' undeclared (first use in this function)
configure:5509: error: (Each undeclared identifier is reported only once
configure:5509: error: for each function it appears in.)
configure:5513: $? = 1
configure: failed program was:
| #line 5483 "configure"
| /* confdefs.h.  */
| 
| #define PACKAGE_NAME "GROMACS"
| #define PACKAGE_TARNAME "gromacs"
| #define PACKAGE_VERSION "3.2.1"
| #define PACKAGE_STRING "GROMACS 3.2.1"
| #define PACKAGE_BUGREPORT "gmx-users at gromacs.org"
| #define PACKAGE "gromacs"
| #define VERSION "3.2.1"
| #define SOFTWARE_INVSQRT
| /* end confdefs.h.  */
| 
| #ifdef F77_DUMMY_MAIN
| #  ifdef __cplusplus
|      extern "C"
| #  endif
|    int F77_DUMMY_MAIN() { return 1; }
| #endif
| int
| main ()
| {
| 
| #ifndef __VEC__
| choke_me
| #endif
| 
|   ;
|   return 0;
| }
configure:5535: result: no
configure:5539: WARNING: no altivec support found - On G4 and later 
Motorola PowerPC
CPUs you can get a HUGE performance gain by using an altivec-enabled 
compiler.
Download the latest devtools from Apple, or gcc-3.1 from ftp.gnu.org


--
Pim Schravendijk - PhD Student
Max Planck Institute for Polymer Research
http://www.mpip-mainz.mpg.de/~schraven/