Near Optimal Hierarchical Encoding of Types

A type inclusion test is a procedure to decide whether two types are related by a given subtyping relationship. An efficient implementation of the type inclusion test plays an important role in the performance of object oriented programming languages with multiple subtyping like C++, Eiffel or Java. There are well-known methods for performing fast constant time type inclusion tests that use a hierarchical bit vector encoding of the partial ordered set representing the type hierarchy. The number of instructions required by the type inclusion test is proportional to the length of those bit vectors. We present a new algorithm based on graph coloring which computes a near optimal hierarchical encoding of type hierarchies. The new algorithm improves significantly on previous results – it is faster, simpler and generates smaller bit vectors.

• Type: Conference
• Year: 1997
• Where: ECOOP
• Authors: Andreas Krall, Jan Vitek, R. Nigel Horspool
• Keywords: Bit Vectors, ECOOP 1997, Programming Languages, Time Type Inclusion, Type Inclusion Test