Refereed article in conference proceedings (A4)
Thick control flows -- An imperative version of stream programming
List of Authors: Jari-Matti Mäkelä, Martti Forsell, Ville Leppänen
Editors: Markus Koskela, Kari Heikkinen
Conference name: Yhdistetyt tietojenkäsittelyn päivät
Publication year: 2014
Book title *: Yhdistetyt tietojenkäsittelypäivät 2014
ISBN: 978-952-265-596-7
We propose thick control flows as a model for defining parallel multi-threaded OO programs, and consider the model's influence on the semantics of ordinary imperative and object-oriented language constructions as well as their implementation by a compiler.
When a thick control flow (in terms of the number of threads) is executing a statement or an expression of a program, all the threads of that flow are considered to execute the same program element synchronously in parallel. Considering method calls, when a control flow with thickness t calls a method, the method is not called separately by each of the t threads, but the control flow calls it only once with t threads. A call stack is not related to each thread but to each of the parallel control flows, since threads do not have program counters -- only control flows have program counters. The concept of thread is only implicit.
The concept of thick control flow makes the programmer to focus on co-operation of few parallel thick control flows instead of a huge number of parallel threads and the implicit synchrony of each thick flow promotes the concept of computation's state, which is essential in achieving correctness.