ForTrilinos Design Document

Abstract

With the development of a Fortran Interface to Trilinos, ForTrilinos, modelers using modern Fortran will be able to provide their codes the capability to use solvers and other capabilities on exascale machines via a straightforward infrastructure that accesses Trilinos. This document outlines what Fortrilinos does and explains briefly how it works. We show it provides a general access to packages via an entry point and uses an xml file from fortran code. With the first release, ForTrilinos will enable Teuchos to take xml parameter lists from Fortran code and set up data structures. It will provide access to linear solvers and eigensolvers. Several examples are provided to illustrate the capabilities in practice. We explain what the user should have already with their code and what Trilinos provides and returns to the Fortran code. We provide information about the build process for ForTrilinos, with a practical example. In future releases, nonlinear solvers, time iteration, advanced preconditioning techniques, and inversion of control (IoC), to enable callbacks to Fortran routines, will be available.