Fortran 90 (F90) is a potential alternative to C++ for breaking the constraints imposed by F77 shortcomings to geophysical inversion research. F90 is an advance over F77 in that it includes the modern idea of information hiding and complex data structures. The most important example of this is an operator like a sparse matrix and its adjoint being initialized by a geophysicist and being used by a mathematical optimizer. Fortran 90 should also offer us some advantages over C++ since compilers exist to parallelize F90, or the closely related HPF (High Performance Fortran), code on a variety of architectures, including our SGI Power Challenge and Connection Machine CM-5.

Both C++ and Fortran 90 have fairly recently matured to the stage where we can purchase compilers on all our general purpose workstations. F90 cannot be expected to reach the levels of conceptual abstraction possible in C++, but as a practical matter, we don't know how badly we really need such powerful abstractions. Also, it is too early to know if F90 will become a standard.

11/11/1997