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2.4. Common Approaches to Concurrent and Parallel Programming
Almasi and Gottlieb’s Taxonomy
Almasi and Gottlieb [1994] use a different taxonomy to classify “most parallel
architectures”. Their taxonomy (cf. Tab. 2.2) is based on two dimensions data
and control, much like Flynn’s. However, the interpretation of these dimensions
is very different. The data mechanism divides the parallel architectures
into being based on shared or private memory. The control mechanism on the
other hand, classifies based on the way control flow is expressed. Their classification
starts with control driven as the category with the most explicit control,
and ends with data driven for mechanism that depend the least on explicit
control flow.
Table 2.2.: Classification of computational models, with examples. [Almasi and Gottlieb,
1994, p. 25]
Data Mechanism
Control Mechanism Shared Memory Private Memory (message passing)
Control driven von Neumann Communicating processes
Pattern driven Logic Actors
Demand driven Graph reduction String reduction
Data driven Dataflow with I-structure Dataflow
While this taxonomy covers a wide range of concurrent and parallel programming
concepts, it does so on a very abstract level. Especially its emphasis
on the control mechanism is of lesser relevance for this dissertation. Since this
research targets contemporary multi-language VMs, all computational models
have to be mapped to a control-driven representation.
A Partial Taxonomy of Contemporary Approaches
Neither Flynn’s nor Almasi and Gottlieb’s taxonomy reflect common concurrent
and parallel programming concepts in a way that facilitates their discussion
in the context of this dissertation. Therefore, this dissertation uses a partial
taxonomy on its own. The following section discusses this taxonomy and
its four categories Threads and Locks, Communicating Threads, Communicating
Isolates, and Data Parallelism. The categorization focuses on how concurrent
and parallel activities interact and coordinate each other, since these aspects
are the main mechanisms exposed to the programmer, and one point which
makes the various concepts distinguishable, even with the necessarily brief
discussions of the concepts in this dissertation.
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