Transformation of Active Reference Graph into Passive Reference Graph for Distributed Garbage Collection

Large-scale distributed computing applications require concurrent programming models that support modular and compositional software development. The actor model supports the development of independent software components with its asynchronous message-passing communication and state encapsulation properties. Automatic actor garbage collection is necessary for high-level actor-oriented programming, but identifying live actors is not as intuitive and easy as identifying live passive objects in a reference graph. However, a transformation method can turn an actor reference graph into a passive object reference graph, which enables the use of passive object garbage collection algorithms and simplifies the problem of actor garbage collection. In this paper, we formally define potential communication by introducing two binary relations - the may-talk-to and the may-transitively-talk-to relations, which are then used to define the set of live actors. We also devise two vertex-preserving transformation methods to transform an actor reference graph into a passive object reference graph. We provide correctness proofs for the proposed algorithms. The experimental results also show that the proposed algorithms are efficient.

Evidence from experiments with single objects indicates that perceiving objects leads to automatic extraction of affordances. Here we examined the influence of implied between-object actions on affordance processing. Images of task-irrelevant object pairs (e.g., a spoon and a bowl) were followed by imperative central targets. Participants made speeded left/right responses to targets, and the responses randomly aligned with the affordance of one of the objects. The orientation of one object was manipulated across trials, leaving the colocation between objects correct or incorrect for potential interaction. Four experiments demonstrated that positioning the objects correctly for between-object actions led to a prioritization of the object active in the action (e.g., the spoon) over the passive (e.g., the bowl) object. Moreover, there was an inhibitory effect on responses to the passive object: responses congruent with the passive object were slower when pairs of objects were shown as if in interaction, compared with when they were not. The effects did not change in the single-hand response task but disappeared when the passive objects were absent-though an affordance should still have been presented by the active object. These results present evidence for affordance selection in action-related object pairs, and suggest inhibition of the action afforded by the passive objects under conditions of affordance competition.

The number of operational satellites and debris objects in the valuable geosynchronous ring has increased steadily over time such that active debris removal missions are necessary to ensure long-term stability. These objects are very large and tumbling, making any mission scenarios requiring physical contact very challenging. In the last 10 years, the concept of using an electrostatic tractor has been investigated extensively. With the electrostatic tractor concept, active charge emission is employed to simultaneously charge the tug or services vehicle, while aiming the charge exhaust onto the passive space debris object to charge it as well. The resulting electrostatic force has been explored to actuate this debris object to a disposal orbit or to detumble the object, all without physical contact. This paper provides a survey of the related research and reviews the charging concepts, the associated electrostatic force and torque modeling, and the feedback control developments, as well as the charge sensing research.

We have seen in the last chapter that in the area of distributed garbage collection algorithms exist, that detect whether one object is garbage depending on the number of references held by others. These other objects fit our definition of a dependency object in Definition 2-1 quite precisely, if we define a parent relation as “holds reference”. The problem of garbage collection is thus similar to the orphan detection problem for mobile agents. Moreover, the path created by local reference counters is similar to the paths in the path concept, i.e. in some algorithms we have an analogue to the problem how an agent can be found. Thus solutions that are similar to those proposed in Chapter 4 for the control of mobile agents have been developed in the area of distributed garbage collection.KeywordsMobile AgentTarget NodeLocal ReferenceGarbage CollectionParent ObjectThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The most significant issue in cities is garbage collection. The average amount of waste a person produces daily rises as the population grows, creating severe waste management issues. Any municipality's most pressing issues are bin status monitoring, locating the shortest route, and vehicle costs. The problem's consequences result in inadequate waste monitoring and management procedures. An effective garbage collection system that periodically measures the amount of garbage in the bins is used to solve these issues. The shortest route can be determined using this bin's status. The vehicle only went to the places where the bins in the city are full. The Wi-Fi module will transmit all of the information to the municipality. The main objective of the proposed work is to create a flexible application that dynamically solve the issue of late bin clearance, poor management of bins etc. The path selection is made by using the Travelling Salesman Algorithm in the Dynamic programming approach. The sensor network is utilized to gather information regarding the garbage contents in the bins and remotely trigger the request for a cleaning process using the Internet of Things. The internet is connected with microcontroller hardware using a Node-MCU device, or ESP8266, a small internet-supporting module that works as a plug-and-play module to any microcontroller. The primary objective of this system is to send information to the municipality and the mobile application regarding the status of the bin, the minimum cost path, the total travel distance, and the kind of vehicle required. This system aims to shorten travel time, save money on diesel and human resources for garbage collection, and improve waste collection and monitoring.

On contemporary cache-coherent Non-Uniform Memory Access (ccNUMA) architectures, applications with a large memory footprint suffer from the cost of the garbage collector (GC), because, as the GC scans the reference graph, it makes many remote memory accesses, saturating the interconnect between memory nodes. We address this problem with NumaGiC, a GC with a mostly-distributed design. In order to maximise memory access locality during collection, a GC thread avoids accessing a different memory node, instead notifying a remote GC thread with a message; nonetheless, NumaGiC avoids the drawbacks of a pure distributed design, which tends to decrease parallelism. We compare NumaGiC with Parallel Scavenge and NAPS on two different ccNUMA architectures running on the Hotspot Java Virtual Machine of OpenJDK 7. On Spark and Neo4j, two industry-strength analytics applications, with heap sizes ranging from 160GB to 350GB, and on SPECjbb2013 and SPECjbb2005, ourgc improves overall performance by up to 45% over NAPS (up to 94% over Parallel Scavenge), and increases the performance of the collector itself by up to 3.6x over NAPS (up to 5.4x over Parallel Scavenge).

This paper addresses the problem of garbage collection in persistent object stores that are multilevel. The proposed approach is able to preserve referential integrity, while ensuring that security is not violated. we first discuss some general principles that should underlie any approach to garbage collection in secure environments. Then, we present a secure garbage collection algorithm, based on the copying approach. >

Landscape architecture is unique as a design practice in its engagement with living nonhumans as instrumental media. However, contemporary landscape architecture theory has struggled to integrate fauna as components of the designed landscape beyond calls to provide and preserve habitat and address the philosophical implications of such a gesture. Animals and other mobile entities, when recognized as integral components of landscapes rather than occasional inhabitants, challenge static notions of landscapes as passive spaces and instead invigorate them as lively events. Some early writings on landscape practice and theory, dating back to the picturesque movement, acknowledge the presence of animals in the landscape. More recently, some landscape designers have imagined new roles for animals. No longer are they passive objects or visitors or inhabitants, blindly providing ecosystem services. Increasingly, these designers have explored the role of animals as active agents shaping the landscape, in ways that reimagine interspecies relationships and subjectivities. Provocations for “animal-aided design” are emblematic of this novel take on the animal in the landscape. Using animacy as a tool for revealing various relational qualities of landscapes, this article joins with calls to attend to the liveliness of other beings as productive and creative agents.

In automatic memory management programming language, the garbage collector is an important feature which reclaims memory that is no longer referenced by the program. The tracing collector performs a transitive closure across the object reference graph. And this process may result in too many cache misses, because the traverse exhibits poor locality. Previous studies have already proposed using software prefetching to improve memory performance of garbage collector. In this work, we studied the characteristic of prefetch instructions on x86 platforms in detail, and proposed a method to control the prefetch ratios by address thresholds. The experimental results show that a further improvement and optimization is obtained by tuning the prefetch ratio. We use these results to devise some guidelines for optimizing the memory performance as well as minimizing the collection pause times.

City of Huntington faces an issue of evenly distributed garbage collection among multiple fleets of trucks on different routes for fair amount of work for workers. This paper describes a method to estimate the weight of garbage picked by the trucks in each block of the city of Huntington based on a hypothesis of a correlation between the total number of stops and the total weight of garbage collected. A device was developed and mounted to the truck to collect data of truck movement. The data was analyzed to generate the number of stops the truck made and the results were compared with the weight of garbage collected throughout the route by a particular truck. Experimental results showed strong correlation between number of stops and garbage collected. Future enhancement is discussed.

In new distributed systems, object mobility is usually allowed and is sometimes used by the underlying object manager system to benefit from object access locality. On the other hand, in-transit references to objects can exist at any moment in asynchronous distributed systems. In the presence of object mobility and in-transit references, many garbage collector (GC) algorithms fail to operate correctly. Others need to use the system's object finder to find the objects while performing their work. As a general principle, a GC should never interfere with object manager polices (such as forcing migration or fixing an object to a given processor). However, if the GC uses the object finder, it will change the access pattern of the system, and eventually it could foul the global allocation policy. In this article we propose a new GC family, Indirect Garbage Collectors, allowing to separate the problems of object management (placement, replication, and retrieval) from garbage collection. This property allows our algorithms to be implemented on top of almost any existent distributed object system, without having to use the object finder.

In this paper, we investigate the formal specification of reactive systems described in an object-oriented style. We define a formalism, called ÉTOILE1-specifications, to deal with concurrent (active) object systems, and propose to extend algebraic approaches to dynamic and concurrent aspects by considering implicit states and implicit transitions, respectively. ÉTOILE-specifications emphasize systems composed of object types. Consequently, the ÉTOILE-formalism is split into two sub-formalisms. The first one enables us to specify the behaviour of object types. Then, it is extended from object types to systems by adding new requirements, mainly to describe the underlying architectural aspects of the system under specification (i.e. relationships between objects). The complexity of real systems results in the definition of formal means to manage their size. To deal with this issue, we propose a refinement of object type specifications by systems in the framework of ÉTOILE-specifications, which enables one to build his(her) specification in an incremental way.

Java runtime frees applications from manual memory management by its automatic garbage collection (GC), at the cost of stop-the-world pauses. State-of-the-art collectors leverage multiple generations, which will inevitably suffer from a full GC phase scanning the whole heap and induce a pause tens of times longer than normal collections, which largely affects both throughput and latency of the entire system. In this paper, we analyze the full GC performance of HotSpot Parallel Scavenge garbage collector comprehensively and study its algorithm design in depth. We find out that heavy dependencies among heap regions cause poor thread utilization. Furthermore, many heap regions contain mostly live objects (referred to as dense regions), which are unnecessary to collect. To solve these problems, we introduce two kinds of optimizations: allocating shadow regions dynamically as compaction destination to eliminate region dependencies and skipping dense regions to reduce GC workload. Evaluation results show the optimizations lead to averagely 2.6X (up to 4.5X) improvement in full GC throughput and thereby boost the application performance by 18.2% on average (58.4% at best).

In this paper, noise spectroscopy has been reported earlier as an efficient tool for enhancing the selectivity of biosensors and the analysis was carried out by desktop spectrum analyzer. There were no reports, however, on the efficacy of this method in complex mixture. We have performed here for the first time, noise spectroscopy analysis on complex mixture of food toxin samples and observed that the first cut-off frequencies are indicative of the fact whether the solution has only specific antigen, mixture of specific and nonspecific antigen or no specific antigen at all. To realize a portable immunosensor, we have developed an electronic interface using digital signal processor (DSP) chip of Microchip Technology which has the embedded Fast Fourier Transform (FFT) algorithm for computation of noise spectrum. The entire system has been successfully demonstrated to detect 0.1 fg/ml aflatoxin B1 (AfB1) from a complex mixture with as high as 1000ng/ml non-specific toxins.

In this paper, we study the current takeaway waste recycling problem and redesign the takeaway waste recycling system under the service design concept. This paper uses a combination of CBR theory and TRIZ theory to analyze and learn from similar cases of garbage collection systems, find and solve conflicts in the take-out garbage collection problem, and thus design a take-out garbage collection system under the service design concept. It provides a sustainable development direction for the existing take-out waste pollution problem and offers the possibility of green development for the whole take-out industry.KeywordsTakeway garbage recyclingGreen designService design