Beltway: Getting Around Garbage Collection Gridlock

We present the design and implementation of a new garbage collection framework that significantly generalizes existing copying collectors. The Beltway framework exploits and separates object age and incrementality. It groups objects in one or more increments on queues called belts, collects belts independently, and collects increments on a belt in first-in-first-out order. We show that Beltway configurations, selected by command line options, act and perform the same as semi-space, generational, and older-first collectors, and encompass all previous copying collectors of which we are aware. The increasing reliance on garbage collected languages such as Java requires that the collector perform well. We show that the generality of Beltway enables us to design and implement new collectors that are robust to variations in heap size and improve total execution time over the best generational copying collectors of which we are aware by up to 40%, and on average by 5 to 10%, for small to moderate heap sizes. New garbage collection algorithms are rare, and yet we define not just one, but a new family of collectors that subsumes previous work. This generality enables us to explore a larger design space and build better collectors

An information approach to the dynamics in farm income: implications for farmland markets

The valuation of farmland is a perennial issue for agricultural policy, given its importance in the farm investment portfolio. Despite the significance of farmland values to farmer wealth, prediction remains a difficult task. This study develops a dynamic information measure to examine the informational content of farmland values and farm income in explaining the distribution of farmland values over time

Estimation of Production Functions using Average Data

Agricultural economists rely on aggregated data at various levels depending on data availability and the econometric techniques employed. However, the implication of aggregation on economic relationships remains an open question. To examine the impact of aggregation on estimation, Monte Carlo techniques and data are employed on production practices.Research Methods/ Statistical Methods,

Financial Appraisal of the Banks for Cooperatives

This study examines the financial situation of the Farm Credit System Banks for Cooperatives using comparative analysis for the period 1978 through 1991. Profitability and leverage measures of the Banks for Cooperatives are compared with similar measures of large commercial banks. The Banks for Cooperatives were found to have performed as well as large commercial banks. Some differences can be explained as compatible with differences in the goals and objectives of a cooperative versus an investor-owned firm. Most differences can be attributed to the financial strength of the Banks for Cooperatives relative to the commercial banking industry.Agribusiness, Agricultural Finance,

Improved TPB-coated Light Guides for Liquid Argon TPC Light Detection Systems

Scintillation light produced in liquid argon (LAr) must be shifted from 128 nm to visible wavelengths in light detection systems used for liquid argon time-projection chambers (LArTPCs). To date, LArTPC light collection systems have employed tetraphenyl butadiene (TPB) coatings on photomultiplier tubes (PMTs) or plates placed in front of the PMTs. Recently, a new approach using TPB-coated light guides was proposed. In this paper, we report on light guides with improved attenuation lengths above 100 cm when measured in air. This is an important step in the development of meter-scale light guides for future LArTPCs. Improvements come from using a new acrylic-based coating, diamond-polished cast UV transmitting acrylic bars, and a hand-dipping technique to coat the bars. We discuss a model for connecting bar response in air to response in liquid argon and compare this to data taken in liquid argon. The good agreement between the prediction of the model and the measured response in liquid argon demonstrates that characterization in air is sufficient for quality control of bar production. This model can be used in simulations of light guides for future experiments.Comment: 25 pages, 20 figure

Resistance and Propulsion Test Results on Two Cb=0.60 Merchant Hull Geosims

http://deepblue.lib.umich.edu/bitstream/2027.42/96607/1/39015087358712.pd

Model Complexity of Program Phases

In resource limited computing systems, sequence prediction models must operate under tight constraints. Various models are available that cater to prediction under these conditions that in some way focus on reducing the cost of implementation. These resource constrained sequence prediction models, in practice, exhibit a fundamental tradeoff between the cost of implementation and the quality of its predictions. This fundamental tradeoff seems to be largely unexplored for models for different tasks. Here we formulate the necessary theory and an associated empirical procedure to explore this tradeoff space for a particular family of machine learning models such as deep neural networks. We anticipate that the knowledge of the behavior of this tradeoff may be beneficial in understanding the theoretical and practical limits of creation and deployment of models for resource constrained tasks

Safe Open-Nested Transactions Through Ownership

Researchers in transactional memory (TM) have proposed open nesting asa methodology for increasing the concurrency of a program. The ideais to ignore certain "low-level" memory operations of anopen-nested transaction when detecting conflicts for its parenttransaction, and instead perform abstract concurrency control for the"high-level" operation that nested transaction represents. Tosupport this methodology, TM systems use an open-nested commitmechanism that commits all changes performed by an open-nestedtransaction directly to memory, thereby avoiding low-levelconflicts. Unfortunately, because the TM runtime is unaware of thedifferent levels of memory, an unconstrained use of open-nestedcommits can lead to anomalous program behavior.In this paper, we describe a framework of ownership-awaretransactional memory which incorporates the notion of modules into theTM system and requires that transactions and data be associated withspecific transactional modules or Xmodules. We propose a newownership-aware commit mechanism, a hybrid between anopen-nested and closed-nested commit which commits a piece of datadifferently depending on whether the current Xmodule owns the data ornot. Moreover, we give a set of precise constraints on interactionsand sharing of data among the Xmodules based on familiar notions ofabstraction. We prove that ownership-aware TM has has cleanmemory-level semantics and can guarantee serializability bymodules, which is an adaptation of multilevel serializability fromdatabases to TM. In addition, we describe how a programmer canspecify Xmodules and ownership in a Java-like language. Our typesystem can enforce most of the constraints required by ownership-awareTM statically, and can enforce the remaining constraints dynamically.Finally, we prove that if transactions in the process of aborting obeyrestrictions on their memory footprint, the OAT model is free fromsemantic deadlock