%T Mobile Data, Dynamic Allocation and Zero Aliasing: An occam Experiment
%A Peter H. Welch,  Frederick R. M. Barnes
%E  Alan G. Chalmers,  Majid Mirmehdi,  Henk Muller
%B Communicating Process Architectures 2001
%X Traditional imperative languages (such as C) and modern
   object\-oriented languages are plagued by uncontrolled
   resource aliasing problems. Add in concurrency and the
   problems compound exponentially. Improperly synchronised
   access to shared (i.e. aliased) resources leads to problems
   of race\-hazard, deadlock, livelock and starvation. This
   paper describes the binding into occam (a concurrent
   processing language based on CSP) of a secure, dynamic and
   efficient way of sharing data between parallel processes
   with minimal synchronisation overheads. The key new
   facilities provided are: a movement semantics for assignment
   and communication, strict zero\-aliasing, apparently dynamic
   memory allocation and automatic
   zero\-or\-very\-small\-unit\-time garbage collection. The
   implementation of this mechanism is also presented, along
   with some initial performance figures (e.g. 80ns for mobile
   communication on an 800 MHz Pentium 3). With occam becoming
   available on a variety of microprocessors for GUI building,
   internet services and small\-memory\-footprint embedded
   products, these capabilities are timely. Lessons are drawn
   for concurrency back in OO languages \- and especially for
   the JCSP (CSP for Java) package library.