Gfortran4

From Vd

GNU fortran compiler

GNU fortran web page. An introduction is found at usage

Compiler flags

Gfortran accept the (mostly) same flag as gcc. The most common compiler flags are :

• -c just compile, do not attempt linking
• -O2 Turn on extensive optimization. This is the default.
• -O3 Even more otimization
• -fomit-frame-pointer Some performance improvement, but makes debugging harder
• -funroll-loops Unroll loops, may yield performance improvement
• -mmmx, -msse, -msse2, -msse3 or -m3dnow Instruct the compiler to use multimedia instructions
• -mtune=opteron tune for the AMD opteron processor
• -ffast-math may improve performance, use with care.

The GNU fortran compilers add a single underscore "_" to symbols. The nm utility can be used to list the symbols in an object file.

[olews@login-0-0 f77]$ nm realft.o
                 U four1_
0000000000000000 T realft_
                 U sin
[olews@login-0-0 f77]$