Just-in-Time Data Structures

Today, software engineering practices focus on finding the single “right ” data representation for a program. The “right” data representation, however, might not exist: changing the representation of an object during program execution can be better in terms of performance. To this end we introduce Just-in-Time Data Structures, which enable representation changes at runtime, based on declarative input from a per-formance expert programmer. Just-in-Time Data Structures are an attempt to shift the focus from finding the “right ” data structure to finding the “right ” sequence of data representa-tions. We present JitDS, a programming language to develop such Just-in-Time Data Structures. Further, we show two ex-ample programs that benefit from changing the representation at runtime