Referencing elements in a reshape expression

[Dominique Dhumieres]

Referencing elements of an array returned by an expressions
is not allowed in Fortran.

Notes that computing the full matrix product for using three
elements only is not very efficient. In addition the matrix
product of small matrices is quite slow with gfortran which
calls a procedure. It is more than an order of magnitude faster
to use dot products instead (in your case you need only three of
them).

Cheers,

Dominique