Type Systems for Distributed Arrays.

Christian Grothoff, Ph.D. Student Computer Science Department UCLA

DEPARTMENT SEMINAR DATE: Monday, March 20, 2006 TIME: 3:00pm PLACE: 271 Thorvaldson This is a recruitment seminar *** Everyone is welcome ***

Abstract

Type-safe languages allow programmers to be more productive by eliminating many kinds of difficult-to-find errors, such as memory corruption. However, type safety comes at a cost in runtime performance due to the need for dynamic safety checks. Traditionally, static analysis is used to eliminate some of these checks; in contrast, our work uses a more powerful type system based upon dependent types to prove the program safe in the absence of such checks. Our work is heavily influenced by X10, a new type-safe object-oriented programming language for distributed high-performance computing. In X10, array accesses are required to be not only in-bounds but also local with respect to the place of execution. Eliminating safety checks for array accesses is important; array accesses are among the most frequent operations in scientific applications, and thus their performance is critical. Experiments show that simple bounds checks in languages like Java can cause performance hits of up to a factor of two. Dynamic checks can be even more costly in X10, since arrays are allowed to be sparse and distributed.

This talk will describe an extension to the type system for X10 that allows the programmer to express that accesses to X10 arrays are both in-bounds and place-local. Joint work with Jens Palsberg and Vijay Saraswat.

About the speaker

Christian Grothoff is a PhD Student at UCLA. He earned an M.S. in Computer Science from Purdue University, and both a Diploma II in Mathematics and the first Staatsexamen in Chemistry from the Bergische Universität Gesamthochschule (BUGH) Wuppertal. His research interests include compilers, programming languages, software engineering, networking and security.

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