What the -fast parameter means?

[tangsk]

when I compile programs with -fast, the output is *.i1 and *.o and cannot be linked?
For example, I want use ifc8.0 work with MPICH, after installed I try to compile the pi3f90.f90 in the example directory.
"mpif90 -c -fast -r8 -i4 -DN_DIM=2 -DMAXBLOCKS=1000 -DNXB=8 -DNYB=8 -DNZB=1 pi3f90.f90 "
will produce pi3f90.o and pi3f90.il
% file pi3f90.il pi3f90.o
pi3f90.il: data
pi3f90.o: ASCII text, with no line terminators

Then how to link them?

[TimP]

-fast includes the -ipo inter-file optimization. You should be able to use your mpif90 command (which invokes ifort)to link such files, but you would not be able to use ld alone. No doubt, you would want to verify operation of your application with lower optimization (e.g. default -O), before trying this more aggressive (and time-consuming to build) option.