here - Stefan-Marr.de

3.1. VM Support for Concurrent and Parallel Programming
wrapper around an object, while Array wraps an array with implicit synchronization.
3.1.2.4. Data Parallelism (DPar)
Surprisingly, none of the VMs examined in this survey expose direct support
for data parallelism. Instead, they are typically accompanied by standard
libraries that build support for parallel programming on top of lowerlevel
abstractions. Examples are the CLI with its library of parallel loop constructs,
the JVM (incl. Dalvik) with its support for fork/join parallelism in
the java.util.concurrent library, 15 and GHC with libraries for map/reduce
parallelism. These libraries are built on top of concepts already available, e. g.,
threads, atomic operations, and locks, and therefore the analyzed VMs do not
provide primitives that expose parallel programming concepts directly.
3.1.2.5. Threats to Validity
Completeness of Selected Subjects The main survey question was: how do
today’s VMs support parallel and concurrent programming approaches? The answer
to this question is based on a set of thirteen VMs. Thus, the number is limited
and the selected set may exclude VMs that provide other mechanisms and expose
them in other ways to the application programmer. However, since the
survey covers contemporary multi-language VMs, and a number of additional
VMs respected for their support for parallel and concurrent programming,
it covers the VMs that are directly relevant for the goal of this dissertation.
Furthermore, the selected VMs reflect common practice in VM support for concurrent
and parallel programming approaches, because the selection includes
the most widely used VMs, as well.
Correctness and Completeness of Results With respect to the concrete survey
questions of which concepts are exposed and how they are exposed, a
number of threats to correctness and completeness of the results need to be
considered.
General Threats to Accuracy As shown in Tab. 3.1, the analysis did not include
the implementations of the CLI and DisVM. Instead, the quality of their
15 http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/packagesummary.html
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