here - Stefan-Marr.de

3.1. VM Support for Concurrent and Parallel Programming
The first question refers to the general set of concepts for concurrent and
parallel programming that is supported by a subject, i. e., the VM under investigation.
Note, the question refers explicitly to language runtime systems instead
of VMs. Thus, the analysis includes concepts provided by the corresponding
standard library as well. Hence, a wider range of concepts is covered and it
becomes possible to determine how the concepts that are directly provided
by the VM are used.
To answer the second question, each concept is assigned to one of the following
four categories:
Implicit Semantics Concepts like the memory models guaranteed by the JVM
and the CLI, or the global interpreter lock semantics used by Python, are
realized by the combined underlying infrastructure instead of a single
mechanism. Thus, overall semantics of the system implicitly supports
the concept by coordinating a wide range of mechanisms.
Instruction Set Architecture (ISA) Concepts that are either supported by a
specific set of opcodes, or concepts which are realized by the structures
which the VM operates on are classified as being part of the instruction
set architecture (ISA). Examples are opcodes to acquire and release
locks, as well as flags in a method header that require the VM to acquire
an object’s lock before executing that method.
Primitive Concepts that require direct access to VM internals but do not fit
into the ISA are typically realized by so-called primitives. They are routines
provided as part of the runtime, implemented in the implementation
language of the VM. Common examples are thread-related operations.
Library Other concepts can be delivered as an integral part of the language
runtime system, but are implemented entirely in terms of other abstractions
provided by the VM, i. e., without requiring new primitives for
their implementation.
Appendix A documents the outline of the questionnaire for this survey in
Lst. A.1. The appendix also includes an example of a completed questionnaire
in Lst. A.2.
3.1.1.2. Survey Subjects
Based on the goal of this dissertation, which is improvementing concurrent
and parallel programming support for multi-language VMs, the focus of this
41