I'm trying to run CAMB on 2 cores (under Cygwin with Mpich2), but I seem to have a problem. Despite the fact that I can see from the task manager that both cores share the load, CAMB takes the same amount of time to run as if it was on one core.
The relevant parts of the makefile are (nothing else is changed):
F90C = g95
FFLAGS = -O2 -DMPI -mno-cygwin -I/cygdrive/c/MPICH2/include
LINKFFLAGS=-L/cygdrive/c/MPICH2/lib -lfmpich2g -lfmpe -lmpi
camb: \$(CAMBOBJ) \$(DRIVER)
\$(F90C) \$(F90FLAGS) \$(CAMBOBJ) \$(DRIVER) \$(LINKFFLAGS) -o \$@
I have successfully run on both cores simple examples, eg that calculate Pi=3.1415..., and I have confirmed that it takes about the half amount of time to run on both cores compared to one, so both g95 and Mpich2 must be working properly.
I'm obviously missing something... Any ideas?
PS g95 does not need a switch like -openmp