The Polaris compiler, which we have co-developed in prior work, was an important influence on the design of our new infrastructure. Polaris is written in C++ and operates on Fortran 77 programs. So far, no extensions have been made to handle Fortran 90, which provides a user-defined type system and other modern programming language features. Polaris' IR is Fortran-oriented and extending it to other languages would require substantial modification.

Another factor we considered was that Polaris was written before the Standard Template Library (C++ STL) became available, so it includes its own container implementations. It uses a pre-ISO dialect of C++ which now seems unusual to programmers and causes many warnings (and sometimes errors) with current compilers. Both aspects limit its portability to other platforms.

In general, Polaris is representative of compilers that are designed for one particular language, serve their purpose well, but are difficult to extend. Cetus should not be thought of as "Polaris for C" because it is designed to avoid that problem. However, there are still several Polaris features that we wanted to adopt in Cetus. Polaris' IR can be printed in the form of code that is similar to the source program. This property makes it easy for a user to review and understand the steps involved in Polaris-generated transformations. Also, Polaris' API is such that the IR is in a consistent state after each call. Common mistakes that pass writers make can be avoided in this way.