Linda Implementation Revisited

Linda is a model for communication and co-ordination of parallel processes. The model provides a virtual shared memory called tuple space, and pri mitives to place tuples into and remove tuples from tuple space. The style of programming provided by Linda is quite different to the style of, say, occam. We describe a new implementation of Linda across a network of transputers. We provide the four Linda primitives, in, out, rd and eval, together with a new prim- itive, collect, developed at York. The implementation focuses on two issues. The first issue is that the ordering of out operations in a sequential process must be preserved if we want Linda to act as a co- ordination langauge. Our implementation provides this. The second issue is the imp- lementation of eval, Linda's mechanism for spawning processes. We outline an im ple- mentation which provides arbitrary spawning of processes which execute concurrently, despite the restriction, enforced by the transputer archit ecture, of declaring a static num- ber of processes at the compilation stage. We provide a small example to show how Linda can be used to write parallel pro- grams, and then outline current work being undertaken at York, which focuses on inter- pretive environments for high level parallel programming l anguages. A prototype Linda implementation and ISETL interpreter have already been developed.