Summary This paper describes ExaShark, a hybrid n‐dimensional array toolkit offered as a high‐level library for scientists to compute large‐scale simulations. It offers a global‐array–like interface while its runtime can be configured to use shared memory threading techniques, inter‐node distribution techniques, or combinations of both. ExaShark takes advantage of the latest HPC technologies, helping to scale to future generation systems. It has been used to develop several scientific applications including stencil codes, solvers, and matrix factorization algorithms. These applications are used to demonstrate that it improves on the state of the art by providing a user‐friendly, generic API without sacrificing performance.

Aspect-oriented programming (AOP) has produced interesting language designs, but also ad hoc semantics that needs clarification. We contribute to this clarification with a calculus that models essential AOP, both simpler and more general than existing formalizations. In AOP, advice may intercept method invocations, and proceed executes the suspended call. Proceed is an ad hoc mechanism, only usable inside advice bodies. Many pointcut mechanisms, for example, wildcards, also lack regularity. We model proceed using first-class closures, and shift complexity from pointcuts to ordinary object-oriented code. Two well-known pointcut categories, call and execution , are commonly considered similar. We formally expose their differences, and resolve the associated soundness problem. Our calculus includes type ranges , an intuitive and concise alternative to explicit type variables that allows advice to be polymorphic over intercepted methods. We use calculus parameters to cover type safety for a wide design space of other features. Type soundness is verified in Coq.

This paper presents an algorithm and a data structure for scalable dynamic synchronization in fine-grained parallelism. The algorithm supports the full generality of phasers with dynamic, two-phase, and point-to-point synchronization. It retains the scalability of classical tree barriers, but provides unbounded dynamicity by employing a tailor-made insertion tree data structure. It is the first completely documented implementation strategy for a scalable phaser synchronization construct. Our evaluation shows that it can be used as a drop-in replacement for classic barriers without harming performance, despite its additional complexity and potential for performance optimizations. Furthermore, our approach overcomes performance and scalability limitations which have been present in other phaser proposals.

Use-site variance approaches such as Java wildcards allows to flexibly derive many co- and contravariant types from one generic class definition. Safety is achieved by restricting the access to members of the parameterized types, but the definition of proper access rules is complicated by the possible nesting of types. Existing approaches for use-site variance relate parameterized classes to bounded existential types and employ a conversion of the type parameters to fresh type variables in order to type an operation. This technique only indirectly explains the operations of a parameterized class and confronts the programmer with type variables which are introduced by the compiler for the purpose of type checking.