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

Exploration of Dynamic Memory

Since the advent of the Java programming language and the development of real-time garbage collection, Java has become an option for implementing real-time applications. The memory management choices provided by real-time garbage collection allow for real-time eJava developers to spend more of their time implementing real-time solutions. Unfortunately, the real-time community is not convinced that real-time garbage collection works in managing memory for Java applications deployed in a real-time context. Consequently, the Real-Time for Java Expert Group formulated the Real-Time Specification for Java (RTSJ) standards to make Java a real-time programming language. In lieu of garbage collection, the RTSJ proposed a new memory model called scopes, and a new type of thread called NoHeapRealTimeThread (NHRT), which takes advantage of scopes. While scopes and NHRTs promise predictable allocation and deallocation behaviors, no asymptotic studies have been conducted to investigate the costs associated with these technologies. To understand the costs associated with using these technologies to manage memory, computations and analyses of time and space overheads associated with scopes and NHRTs are presented. These results provide a framework for comparing the RTSJ’s memory management model with real-time garbage collection. Another facet of this research concerns the optimization of novel approaches to garbage collection on multiprocessor systems. Such approaches yield features that are suitable for real-time systems. Although multiprocessor, concurrent garbage collection is not the same as real-time garbage collection, advancements in multiprocessor concurrent garbage collection have demonstrated the feasibility of building low latency multiprocessor real-time garbage collectors. In the nineteen-sixties, only three garbage collection schemes were available, namely reference counting garbage collection, mark-sweep garbage collection, and copying garbage collection. These classical approaches gave new insight into the discipline of memory management and inspired researchers to develop new, more elaborate memory-management techniques. Those insights resulted in a plethora of automatic memory management algorithms and techniques, and a lack of uniformity in the language used to reason about garbage collection. To bring a sense of uniformity to the language used to reason about garbage collection technologies, a taxonomy for comparing garbage collection technologies is presented

Garbage collection can be made real-time and verifiable

An efficient means of memory reclamation (also known as Garbage Collection) is essential for Machine Intelligence applications where dynamic storage allocation is desired or required. Solutions for real-time systems must introduce very small processing overhead and must also provide for the verification of the software in order to meet the application time budgets and to verify the correctness of the software. Garbage Collection (GC) techniques are proposed for symbolic processing systems which may simultaneously meet both real-time requirements and verification requirements. The proposed memory reclamation technique takes advantage of the strong points of both the earlier Mark and Sweep technique and the more recent Copy Collection approaches. At least one practical implementation of these new GC techniques has already been developed and tested on a very-high performance symbolic computing system. Complete GC processing of all generated garbage has been demonstrated to require as little as a few milliseconds to perform. This speed enables the effective operation of the GC function as either a background task or as an actual part of the application task itself

Lock-free atom garbage collection for multithreaded Prolog

The runtime system of dynamic languages such as Prolog or Lisp and their derivatives contain a symbol table, in Prolog often called the atom table. A simple dynamically resizing hash-table used to be an adequate way to implement this table. As Prolog becomes fashionable for 24x7 server processes we need to deal with atom garbage collection and concurrent access to the atom table. Classical lock-based implementations to ensure consistency of the atom table scale poorly and a stop-the-world approach to implement atom garbage collection quickly becomes a bottle-neck, making Prolog unsuitable for soft real-time applications. In this article we describe a novel implementation for the atom table using lock-free techniques where the atom-table remains accessible even during atom garbage collection. Relying only on CAS (Compare And Swap) and not on external libraries, the implementation is straightforward and portable. Under consideration for acceptance in TPLP.Comment: Paper presented at the 32nd International Conference on Logic Programming (ICLP 2016), New York City, USA, 16-21 October 2016, 14 pages, LaTeX, 4 PDF figure

Garbage collection in distributed systems

PhD ThesisThe provision of system-wide heap storage has a number of advantages. However, when the technique is applied to distributed systems automatically recovering inaccessible variables becomes a serious problem. This thesis presents a survey of such garbage collection techniques but finds that no existing algorithm is entirely suitable. A new, general purpose algorithm is developed and presented which allows individual systems to garbage collect largely independently. The effects of these garbage collections are combined, using recursively structured control mechanisms, to achieve garbage collection of the entire heap with the minimum of overheads. Experimental results show that new algorithm recovers most inaccessible variables more quickly than a straightforward garbage collection, giving an improved memory utilisation

Finer garbage collection in LINDACAP.

As open systems persist, garbage collection (GC) can be a vital aspect in managing system resources. Although garbage collection has been proposed for the standard Linda, it was a rather course-grained mechanism. This finer-grained method is offered in Lindacap, a capability-based coordination system for open distributed systems. Multicapabilities in Lindacap enable tuples to be uniquely referenced, thus providing sufficient information on the usability of tuples (data) within the tuple-space. This paper describes the garbage collection mechanism deployed in Lindacap, which involves selectively garbage collecting tuples within tuple-spaces. The authors present the approach using reference counting, followed by the tracing (mark-and-sweep) algorithm to garbage collect cyclic structures. A time-to-idle (TTI) technique is also proposed, which allows for garbage collection of multicapability regions that are being referred to by agents but are not used in a specified length of time. The performance results indicate that the incorporation of garbage collection techniques adds little overhead to the overall performance of the system. The difference between the average overhead caused by the mark-and-sweep and reference counting is small, and can be considered insignificant if the benefits brought by the mark-and-sweep is taken into account

PERILAKU PETUGAS PENGUMPUL SAMPAH UNTUK MELINDUNGI DIRINYA DARI PENYAKIT BAWAAN SAMPAH DI WILAYAH PATANGPULUHAN YOGYAKARTA TAHUN 2009

Background : Human activities in using of nature always leaving the rest that are consideredare not useful anymore, so treated as waste products, namely garbage and waste. If the wasteis not managed properly, it will negatively impact health. Therefore there is need for theprevention of negative influences to avoid or use personal protective. The purpose of thisresearch is to know knowledge about the types of garbage collectors , the knowledge workers ofthe garbage collector garbage congenital diseases, and the behavior of garbage collectionworkers in protecting themselves against inherited diseases.Methods: This kind of research is the research evaluation, which includes the formativeevaluation (emphasis on process rather than product). While the research approach used isqualitative. Research subjects in this study are to garbage collectors officers Dumpster (TPS)which use pushcart. Data collection techniques will be used is the observation by participating(participation observation), and in-depth interviews (in-depth Interviewing). Techniques of dataanalysis performed using data reduction, data display the data verification.Conclusion : The conclusions to be drawn from this study are: First, knowledge about the typesof garbage collectors personal protection device which must be worn during most of the work isstill lacking. Second, the knowledge workers of the garbage collector garbage congenitaldiseases mostly still less understood. Third, the behavior of garbage collection workers inprotecting themselves against inherited diseases is less trash to the efforts carried out beforetouching the garbage, and is good for the efforts undertaken after touching garbage. All of themare supported by the lack or ignorance of understanding about self health (Hygiene Sanitation).Keywords: Behavior, personal protection device, congenital disease tras

Unified concurrent write barrier

In a programming language with support for garbage collection, a write barrier is a code snippet that maintains the key invariants of the garbage collector. The write barrier is typically executed after a write operation. The write barrier is computationally expensive and can impact program performance. This is true to a greater extent for languages where garbage collectors need to maintain multiple sets of invariants. For example, languages that employ garbage collection schemes with two collectors may maintain their invariants using multiple different write barriers. The techniques of this disclosure address the problem of maintaining multiple invariants by unifying the write barriers and by executing computationally expensive parts of the write barrier in a concurrent thread