9 research outputs found
Streamlining Progress-Based Derivations of Concurrent Programs
Get PDFThe logic of Owicki and Gries is a well known logic for verifying safety properties of concurrent programs. Using this logic, Feijen and van Gasteren describe a method for deriving concurrent programs based on safety. In this work, we explore derivation techniques of concurrent programs using progress-based reasoning. We use a framework that combines the safety logic of Owicki and Gries, and the progress logic of UNITY. Our contributions improve the applicability of our earlier techniques by reducing the calculational overhead in the formal proofs and derivations. To demonstrate the effectiveness of our techniques, a derivation of Dekker's mutual exclusion algorithm is presented. This derivation leads to the discovery of some new and simpler variations of this famous algorithm
The Problem of Mutual Exclusion: A New Distributed Solution
Get PDFIn both centralized and distributed systems, processes cooperate and compete with each other to access the system resources. Some of these resources must be used exclusively. It is then required that only one process access the shared resource at a given time. This is referred to as the problem of mutual exclusion. Several synchronization mechanisms have been proposed to solve this problem. In this thesis, an effort has been made to compile most of the existing mutual exclusion solutions for both shared memory and message-passing based systems. A new distributed algorithm, which uses a dynamic information structure, is presented to solve the problem of mutual exclusion. It is proved to be free from both deadlock and starvation. This solution is shown to be economical in terms of the number of message exchanges required per critical section execution. Procedures for recovery from both site and link failures are also given
Submicron Systems Architecture Project : Semiannual Technical Report
Get PDFThe Mosaic C is an experimental fine-grain multicomputer
based on single-chip nodes. The Mosaic C chip includes 64KB of fast dynamic RAM,
processor, packet interface, ROM for bootstrap and self-test, and a two-dimensional selftimed
router. The chip architecture provides low-overhead and low-latency handling of
message packets, and high memory and network bandwidth. Sixty-four Mosaic chips are
packaged by tape-automated bonding (TAB) in an 8 x 8 array on circuit boards that can, in
turn, be arrayed in two dimensions to build arbitrarily large machines. These 8 x 8 boards are
now in prototype production under a subcontract with Hewlett-Packard. We are planning
to construct a 16K-node Mosaic C system from 256 of these boards. The suite of Mosaic
C hardware also includes host-interface boards and high-speed communication cables. The
hardware developments and activities of the past eight months are described in section 2.1.
The programming system that we are developing for the Mosaic C is based on the
same message-passing, reactive-process, computational model that we have used with earlier
multicomputers, but the model is implemented for the Mosaic in a way that supports finegrain
concurrency. A process executes only in response to receiving a message, and may in
execution send messages, create new processes, and modify its persistent variables before
it either exits or becomes dormant in preparation for receiving another message. These
computations are expressed in an object-oriented programming notation, a derivative of
C++ called C+-. The computational model and the C+- programming notation are
described in section 2.2. The Mosaic C runtime system, which is written in C+-, provides
automatic process placement and highly distributed management of system resources. The
Mosaic C runtime system is described in section 2.3
