Posted by Tobias Burnus on January 31, 2007 at 01:18:09:
In Reply to: Re: Compilation with gfortran posted by Valera on December 22, 2006 at 21:06:38:
: in case you really want to compile molcas with gfortran - you should use a special configuration file:
: ./configure -compiler gf
: (Note, that gf.comp was developed for 32-bit OS, if you are using 64-bit computer - like AMD64 - some modifications should be made for compilation options, and GATARGET should be set to LINUX64)
Note that the option "-malign-double" causes a lot of trouble as it changes the Application Binary Interface (ABI). This makes libgfortran (which contains the IO routines) incompatible with the program itself!
: However, you should be aware that gfortran generates a code which is 30-40% slower
: than g77.
I don't have any g77 numbers, but at least with the proper options, gfortran for the Polyhedron test suite only 6% slower than the Intel Fortran Compiler and only 15% slower than Pathscale which is seemingly the fastest compiler for AMD64. Thus I don't think this is generally true.
gfortran -O is however slower than g77 -O, but with -O2 or -O3 -fvectorize-tree, gfortran outperforms g77 for the most programs.
If you have a (relatively) small test program where gfortran is slower than g77, I'm interested.
Tobias
occasional gfortran developer