Structure Vectors and their Implementation

The typical representation of structures (a.k.a. records) includes a header and type descriptor that are a considerable overhead when the structures have few fields and the program allocates a large number of them. We propose structure vectors that group many structures of the same type, removing the need for a header and type descriptor for each contained structure. This paper describes our implementation of structure vectors within the Gambit Scheme system. Microbenchmarks indicate that structure allocation is faster, structure access is roughly the same speed, and type checking is substantially slower. On real applications we have observed speedups of 7% to 15%.