1,413 research outputs found
Introspective Pushdown Analysis of Higher-Order Programs
In the static analysis of functional programs, pushdown flow analysis and
abstract garbage collection skirt just inside the boundaries of soundness and
decidability. Alone, each method reduces analysis times and boosts precision by
orders of magnitude. This work illuminates and conquers the theoretical
challenges that stand in the way of combining the power of these techniques.
The challenge in marrying these techniques is not subtle: computing the
reachable control states of a pushdown system relies on limiting access during
transition to the top of the stack; abstract garbage collection, on the other
hand, needs full access to the entire stack to compute a root set, just as
concrete collection does. \emph{Introspective} pushdown systems resolve this
conflict. Introspective pushdown systems provide enough access to the stack to
allow abstract garbage collection, but they remain restricted enough to compute
control-state reachability, thereby enabling the sound and precise product of
pushdown analysis and abstract garbage collection. Experiments reveal
synergistic interplay between the techniques, and the fusion demonstrates
"better-than-both-worlds" precision.Comment: Proceedings of the 17th ACM SIGPLAN International Conference on
Functional Programming, 2012, AC
Back-traced Garbage Collection
This disclosure describes back-traced garbage collection in a computer. A back-traced garbage collector searches backwards from an object in an object graph, until a root node is encountered, or until there are no further objects to search. If a root node is not encountered, the searched objects are unreachable and are deleted. The garbage collector can run incrementally, process portions of the object graph, and determine reachability of individual objects without examining the entire object graph. The garbage collector has low latency. The garbage collector is tunable, for example, in response to program characteristics and performance requirements
Pruning, Pushdown Exception-Flow Analysis
Statically reasoning in the presence of exceptions and about the effects of
exceptions is challenging: exception-flows are mutually determined by
traditional control-flow and points-to analyses. We tackle the challenge of
analyzing exception-flows from two angles. First, from the angle of pruning
control-flows (both normal and exceptional), we derive a pushdown framework for
an object-oriented language with full-featured exceptions. Unlike traditional
analyses, it allows precise matching of throwers to catchers. Second, from the
angle of pruning points-to information, we generalize abstract garbage
collection to object-oriented programs and enhance it with liveness analysis.
We then seamlessly weave the techniques into enhanced reachability computation,
yielding highly precise exception-flow analysis, without becoming intractable,
even for large applications. We evaluate our pruned, pushdown exception-flow
analysis, comparing it with an established analysis on large scale standard
Java benchmarks. The results show that our analysis significantly improves
analysis precision over traditional analysis within a reasonable analysis time.Comment: 14th IEEE International Working Conference on Source Code Analysis
and Manipulatio
Liveness-Based Garbage Collection for Lazy Languages
We consider the problem of reducing the memory required to run lazy
first-order functional programs. Our approach is to analyze programs for
liveness of heap-allocated data. The result of the analysis is used to preserve
only live data---a subset of reachable data---during garbage collection. The
result is an increase in the garbage reclaimed and a reduction in the peak
memory requirement of programs. While this technique has already been shown to
yield benefits for eager first-order languages, the lack of a statically
determinable execution order and the presence of closures pose new challenges
for lazy languages. These require changes both in the liveness analysis itself
and in the design of the garbage collector.
To show the effectiveness of our method, we implemented a copying collector
that uses the results of the liveness analysis to preserve live objects, both
evaluated (i.e., in WHNF) and closures. Our experiments confirm that for
programs running with a liveness-based garbage collector, there is a
significant decrease in peak memory requirements. In addition, a sizable
reduction in the number of collections ensures that in spite of using a more
complex garbage collector, the execution times of programs running with
liveness and reachability-based collectors remain comparable
A Story of Parametric Trace Slicing, Garbage and Static Analysis
This paper presents a proposal (story) of how statically detecting
unreachable objects (in Java) could be used to improve a particular runtime
verification approach (for Java), namely parametric trace slicing. Monitoring
algorithms for parametric trace slicing depend on garbage collection to (i)
cleanup data-structures storing monitored objects, ensuring they do not become
unmanageably large, and (ii) anticipate the violation of (non-safety)
properties that cannot be satisfied as a monitored object can no longer appear
later in the trace. The proposal is that both usages can be improved by making
the unreachability of monitored objects explicit in the parametric property and
statically introducing additional instrumentation points generating related
events. The ideas presented in this paper are still exploratory and the
intention is to integrate the described techniques into the MarQ monitoring
tool for quantified event automata.Comment: In Proceedings PrePost 2017, arXiv:1708.0688
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