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Nondeterminism and Concurrency

Deterministic programs
- Same input always produces same output.
- Evaluation strategy need not be unique.
- Example: side effect-free arithmetic addition.
Nondeterministic programs
- Several evaluation strategies allowed.
- Different strategies lead to different outputs.
- Bad design: addition with side effects.
- Acceptable: simultaneous requests to a server.
Parallel evaluation
- Noninterfering parallelism: simultaneous evaluation of subparts does not interact.
- Interfering parallelism: interaction exists, relative speeds affect final result.
- Concurrent languages: interfering parallelism.

Can sequential semantics be generalized?

Wolfgang.Schreiner@risc.uni-linz.ac.at
Id: intro.tex,v 1.2 1996/01/31 15:37:03 schreine Exp schreine