############################################################
# Building 'tdgesv' and sample output on physics, a Sun 4
# Ultra-Enterprise running SunOS 5.6
#############################################################
physics% pwd; ls
/export/ugrad/phys410/linsys/ex1
Makefile   tdgesv.f

physics% make
f77 -O -c tdgesv.f
tdgesv.f:
 MAIN tdgesv1:
f77 -O -L/home5/choptuik/lib tdgesv.o -llapack  -o tdgesv
Undefined			first referenced
 symbol  			    in file
dscal_         /usr/local/lib/liblapack.a(dgetf2.o)
dswap_         /usr/local/lib/liblapack.a(dlaswp.o)
dtrsm_         /usr/local/lib/liblapack.a(dgetrf.o)
idamax_        /usr/local/lib/liblapack.a(dgetf2.o)
dgemm_         /usr/local/lib/liblapack.a(dgetrf.o)
dger_          /usr/local/lib/liblapack.a(dgetf2.o)
ld: fatal: Symbol referencing errors. No output written to tdgesv
make: [tdgesv] Error 1 (ignored)
############################################################
# OOPS ... those are references to BLAS routines!  I haven't 
# defined the environment variable LIBBLAS which is used in the 
# Makefile.  Best to add a line in ~/.cshrc.user.  Arguably, 
# '-lblas' should just be in the Makefile.  However, on SOME 
# systems, BLAS is effectively "built-in", and then explicit 
# reference to it can cause problems at load time.  With the 
# current mechanism, we can easily deal with such a case 
# simply by leaving the environment variable undefined on 
# those systems.
############################################################
physics% vi ~/.cshrc.user

     INSERT ---->   setenv  LIBBLAS  '-lblas'


############################################################
# "Activate" the changed .cshrc_user; among other things this 
# will set LIBBLAS properly.
############################################################
physics% source !$
source ~/.cshrc.user

[47]physics{phys410} set prompt="physics% "

physics% pwd; ls
/export/ugrad/phys410/linsys/ex1
Makefile   tdgesv.f   tdgesv.o

############################################################
# This time the build works ...
############################################################
physics% make 
f77 -O -L/home5/choptuik/lib tdgesv.o -llapack -lblas -o tdgesv

############################################################
# ... and we get output consistent with the other systems.
############################################################
physics% tdgesv
     5.4263644124316  -0.32577537681739  -0.40835080698946