By combining existing type systems with standard typebased compilation techniques, we describe how to write strongly typed programs that include a function that acts as a tracing garbage collector for the program. Since the garbage collector is an explicit function, we do not need to provide a trusted garbage collector as a runtime service to manage memory. Since our language is strongly typed, the standard type soundness guarantee "Well typed programs do not go wrong" is extended to include the collector. Our type safety guarantee is non-trivial since not only does it guarantee the type safety of the garbage collector, but it guarantees that the collector preservers the type safety of the program being garbage collected. We describe the technique in detail and report performance measurements for a few microbenchmarks as well as sketch the proofs of type soundness for our system. 1 Introduction We outline an approach, based on ideas from existing type systems, to build a type-preser...

If a fixed exponentially decreasing probability distribution function is used to model every object’s lifetime, then the age of an object gives no information about its future life expectancy. This radioactive decay model implies there can be no rational basis for deciding which live objects should be promoted to another generation. Yet there remains a rational basis for deciding how many objects to promote, when to collect garbage, and which generations to collect. Analysis of the model leads to a new kind of generational garbage collector whose effectiveness does not depend upon heuristics that predict which objects will live longer than others. This result provides insight into the computational advantages of generational garbage collection, with implications for the management of objects whose life expectancies are difficult to predict. 1

Generational collection has improved the efficiency of garbage collection in fast-allocating programs by focusing on collecting young garbage, but has done little to reduce the cost of collecting a heap containing large amounts of older data. A new generational technique, older-first collection, shows promise in its ability to manage older data.

We propose a type-based technique to analyze how many times each value, including communication channels, is used during execution of concurrent programs. This work is closely related with the recent work by Kobayashi, Pierce, and Turner on a linear channel system on a process calculus. They introduced a type system that ensures certain channels (called linear channels) to be used just once, and showed that how linear channels help reasoning about program behaviors. However, they only deal with a pure message passing calculus, and more importantly, the type reconstruction problem is left open. This thesis develops a type reconstruction algorithm of a variant of a linear channel type system for a concurrent language with data constructors such as records, and let-polymorphism. We can detect not only linear channels but also other used-once values (closures, records, etc.) by the type reconstruction algorithm. Computational cost of our analysis (excluding cost of ordinary type reconstruc...