Consistency Tradeoffs Research Articles

Testing the Terminal Investment Hypothesis in California Oaks.

The terminal investment hypothesis-which proposes that reproductive investment should increase with age-related declines in reproductive value-has garnered support in a range of animal species but has not been previously examined in long-lived plants, such as trees. We tested this hypothesis by comparing relative acorn production and radial growth among 1,000+ mature individuals of eight species of California oaks (genus Quercus) followed for up to 37 years, during which time 70 trees died apparently natural deaths. We found no significant differences in the radial growth, acorn production, or index of reproductive effort, taking into consideration both growth and reproduction among dying trees relative to either conspecific trees at the same site that did not die or growth and reproduction from earlier years for the focal trees that did eventually die. Furthermore, we found no consistent trade-off between growth and reproduction among trees that died, nor did dying trees significantly alter their relative investment in reproduction even as they underwent physical decline. Trees approaching the end of their lives are often in poor physical condition but do not appear to differentially invest more of their diminished resources in reproduction compared with healthy trees.

Inadequacies of CAP Theorem

In today's technical world, we are witnessing a strong and increasing desire to scale systems to successfully complete workloads in a reasonable time frame. As a result of this scaling, an additional penalty of complexity is incurred in the system. In this paper, we have explained the tradeoffs that have to be taken into consideration while designing databases using CAP theorem and the consequences of this tradeoff. Problems of the CAP theorem itself and its limitations are discussed. CAP theorem which was able to meet the demands, back when it was proposed, can't catch up to the current requirements. The problem lies in the open-ended definitions of CAP which are subject to interpretations. PACELC is an alternative to CAP and is able to overcome some of its current problems. PACELC builds on the CAP theorem and it goes one step ahead of CAP by stating that a trade-off also exists, this time between latency and consistency, provides a more complete portrayal of the potential consistency tradeoffs for distributed systems. General Terms CAP, PACELC.

Exploring VM Introspection

While there are a variety of existing virtual machine introspection (VMI) techniques, their latency, overhead, complexity and consistency trade-offs are not clear. In this work, we address this gap by first organizing the various existing VMI techniques into a taxonomy based upon their operational principles, so that they can be put into context. Next we perform a thorough exploration of their trade-offs both qualitatively and quantitatively. We present a comprehensive set of observations and best practices for efficient, accurate and consistent VMI operation based on our experiences with these techniques. Our results show the stunning range of variations in performance, complexity and overhead with different VMI techniques.We further present a deep dive on VMI consistency aspects to understand the sources of inconsistency in observed VM state and show that, contrary to common expectation, pause-and-introspect based VMI techniques achieve very little to improve consistency despite their substantial performance impact.

Relaxing data consistency along different dimensions for increasing operation availabilities

Pessimistic quorum-based data replication strategies have strictly upper-bounded operation availabilities. The probabilistic relaxation of their strict consistency notion along different dimensions permits to overcome this upper-bound. The resulting probabilistic replication strategies allow the exploitation of the data consistency versus operation availabilities trade-off. In our approaches, we add a certain number of probabilistically intersecting quorums to the originally strictly intersecting partially ordered quorum system in order to ‘closely conserve’ its original characteristic behaviour. As one expects, the number and nature of probabilistic quorums added have a strong impact on the particular trade-off. We present two algorithms for the generation of probabilistic quorums based on input strict quorums. Furthermore, the order in which probabilistic and strict quorums are to be probed and used for executing operations is also very important. We relate three general strategies of ordering the probabilistic and strict quorums of those probabilistic quorum systems (PQSs), evaluate their impact on the data consistency versus operation availabilities trade-off and compare them in terms of this trade-off. The evaluation uses Markov chain-based steady-state analysis applied to a representative instance of PQSs with adequate partial orderings.

Hidden responses to environmental variation: maternal effects reveal species niche dimensions

Species responses to fluctuating environments structure population and community dynamics in variable ecosystems. Although offspring number is commonly used to measure these responses, maternal effects on offspring quality may be an important but largely unrecognised determinant of long-term population growth. We selected 29 species across a Mediterranean annual plant phylogeny, and grew populations of each species in wet and dry conditions to determine responses in seed number and maternal effects (seed size, seed dormancy, and seedling growth). Maternal effects were evident in over 40% of species, but only 24% responded through seed number. Despite a strong trade-off between seed size and seed number among species, there was no consistent trade-off within species; we observed correlations that ranged from positive to negative. Overall, species in this plant guild show a complex range of responses to environmental variation that may be underestimated when only seed number responses are considered.

Quantifying eventual consistency with PBS

Data store replication results in a fundamental trade-off between operation latency and data consistency. At the weak end of the consistency spectrum is eventual consistency providing no limit to the staleness of data returned. However, anecdotally, eventual consistency is often “good enough” for practitioners given its latency and availability benefits. In this work, we explain why eventually consistent systems are regularly acceptable in practice, analyzing both the staleness of data they return and the latency benefits they offer. We introduce Probabilistically Bounded Staleness (PBS), a consistency model which provides expected bounds on data staleness with respect to both versions and wall clock time. We derive a closed-form solution for versioned staleness as well as model real-time staleness under Internet-scale production workloads for a large class of quorum-replicated, Dynamo-style stores. Using PBS, we measure the latency–consistency trade-off for partial, non-overlapping quorum systems, including limited multi-object operations. We quantitatively demonstrate how and why eventually consistent systems frequently return consistent data within tens of milliseconds while offering significant latency benefits.

Consistency Tradeoffs in Modern Distributed Database System Design: CAP is Only Part of the Story

The CAP theorem's impact on modern distributed database system design is more limited than is often perceived. Another tradeoff-between consistency and latency -has had a more direct influence on several well-known DDBSs. A proposed new formulation, PACELC, unifies this tradeoff with CAP.

Decisions at a glance: The relative cost of multiple possible actions is represented in conscious perception of spatial layout

Prior to performing a physical action in the environment, decisions must be made to select one from multiple potential actions and then from multiple ways of performing it. One of the chief factors involved in such decisions is the effort required to perform the action. Noting that effort can be difficult to measure, Rosenbaum, Brach, and Semenov (2010) implemented a two-alternative forced choice action procedure that required participants to choose between a short or long reach across a table to pick up a bucket, with the constraint that the choice would also determine how far they had to carry the bucket. Participants' action choices demonstrated a consistent trade-off between the costs of walking and reaching, indicating that the effort involved in individual components of an action sequence play a combined, predictable role in the choice of how to act. In the current study, we replicated their design with several additions. Of primary interest, participants' perception of one potential carrying distance was assessed on each trial prior to performing the actions. When the distance being estimated was one that they believed to require less combined reaching/walking effort (as indicated by the fact that they would later choose to carry the bucket over that distance instead of the alternative choice), the distance was perceived as shorter, and conversely when the distance being estimated was the one they believed to require more combined effort (i.e. they would later choose to carry the bucket over the alternate distance), the distance being estimated appeared farther. Thus, perception of a single component in an action sequence (distance to be walked) was influenced by a second component as well: the effort required to reach. In this respect, it may be that changes to conscious perception of spatial layout serve in part to guide complex action choices.

How Does the Fortune’s Formula Kelly CapitalGrowth Model Perform?

William Poundstone’s book, <i>Fortune’s Formula</i>, brought the Kelly capital growth criterion to the attention of investors. But how do full and fractional Kelly strategies perform in practice? The authors study three simple investment situations and simulate the behavior of these strategies over medium-term horizons using a large number of scenarios. The results show 1) the great superiority of full Kelly and close-to-full Kelly strategies over longer horizons in that they earn very large gains a large fraction of the time, 2) the very risky short-term performance of Kelly and high-fractional Kelly strategies, 3) a consistent trade-off of growth versus security as a function of the bet size determined by the various strategies, and 4) no matter how favorable the investment opportunities are, or how long the finite horizon is, a sequence of bad scenarios can lead to very poor final wealth outcomes with a loss of most of the investor’s initial capital. Hence, in practice, financial engineering is important for dealing with the short-term volatility and long-run situations in a sequence of bad scenarios. Properly used, however, the strategy has much to commend it, especially in trading with many repeated investments. <b>TOPICS:</b>Financial crises and financial market history, volatility measures, statistical methods

Phylogenetic comparative analysis of electric communication signals in ghost knifefishes (Gymnotiformes: Apteronotidae)

Electrocommunication signals in electric fish are diverse, easily recorded and have well-characterized neural control. Two signal features, the frequency and waveform of the electric organ discharge (EOD), vary widely across species. Modulations of the EOD (i.e. chirps and gradual frequency rises) also function as active communication signals during social interactions, but they have been studied in relatively few species. We compared the electrocommunication signals of 13 species in the largest gymnotiform family, Apteronotidae. Playback stimuli were used to elicit chirps and rises. We analyzed EOD frequency and waveform and the production and structure of chirps and rises. Species diversity in these signals was characterized with discriminant function analyses, and correlations between signal parameters were tested with phylogenetic comparative methods. Signals varied markedly across species and even between congeners and populations of the same species. Chirps and EODs were particularly evolutionarily labile, whereas rises differed little across species. Although all chirp parameters contributed to species differences in these signals, chirp amplitude modulation, frequency modulation (FM) and duration were particularly diverse. Within this diversity, however, interspecific correlations between chirp parameters suggest that mechanistic trade-offs may shape some aspects of signal evolution. In particular, a consistent trade-off between FM and EOD amplitude during chirps is likely to have influenced the evolution of chirp structure. These patterns suggest that functional or mechanistic linkages between signal parameters (e.g. the inability of electromotor neurons increase their firing rates without a loss of synchrony or amplitude of action potentials) constrain the evolution of signal structure.

Janus phenomenon: the interrelated tradeoffs inherent in therapies designed to enhance collateral formation and those designed to inhibit atherogenesis.

normous advances have occurred in the understanding ofthe molecular and cellular mechanisms responsible forboth collateral development (collaterogenesis*) and athero-genesis. This advancement has been accompanied by paralleladvances in therapies designed to enhance collaterals and toinhibit the development and progression of atherosclerosis.Our laboratory has been interested in both areas, and duringour work, we noticed a consistent tradeoff: Whatever inter-vention enhanced collaterals increased atherogenesis and visaversa. We refer to this tradeoff as the Janus phenomenon.†This observation, if correct, is of more than passing interestgiven the many antiatherosclerotic interventions used inpatients and the proangiogenic interventions being tested thatmay soon be used therapeutically. Therefore, if the Janusphenomenon is real, its clinical implications would be ofcritical importance. Equally as important, the concept mightprovide mechanistic insights into both atherogenesis andcollaterogenesis.Consequently, we began to track phenomena compatiblewith the Janus concept. Table 1 lists a few molecules forwhich reasonable evidence exists relating to both their ath-erosclerotic and collaterogenic effects and the actions ofwhich are compatible with the Janus phenomenon.

Protection of Geoprivacy and Accuracy of Spatial Information: How Effective Are Geographical Masks?

Spatial analysis and mapping of georeferenced, individual-level data can help identify important geographical patterns or lead to knowledge significant for dealing with specific social issues in a particular area. However, given the need to protect personal privacy when using geospatial data, the possibility for undertaking geographical analysis on certain types of individual-level data is becoming increasingly circumscribed. This article addresses the need to protect geoprivacy while making georeferenced, individual-level data available in such a way that analytical results are not significantly affected. The effectiveness of three geographical masks with different perturbation radii (r) is examined using a data set for lung-cancer deaths in Franklin County, Ohio, in 1999. The findings reveal a rather consistent trade-off between data confidentiality and accuracy of analytical results. There seems to be a threshold r-value at which the results of analyses on masked data become substantially different from the original results. An r that produces an area about the average size of the study-area census-block groups achieves a desirable optimum trade-off between privacy protection and accuracy of results. The study shows that implementing appropriate geographical masks may help data managers or researchers establish the desirable trade-off, in a particular context, between privacy protection and accuracy of geographic information.

Global apparel production and sweatshop labour: can raising retail prices finance living wages?

This paper provides some empirical evidence on issues raised by the global anti-sweatshop movement. We first consider the relationship between wage and employment growth, finding no consistent trade-off between them. We then measure the share of labour costs in the production of garments in the US and Mexico. We find that the retail price increases necessary to absorb the costs of raising wages substantially are small, well within the range of price increases that polls suggest US consumers are willing to pay. We close by considering some implications of these results.

Global Apparel Production and Sweatshop Labor: Can Raising Retail Prices Finance Living Wages?

This paper provides some empirical evidence on issues raised by the global anti-sweatshop movement. We first consider the relationship between wage and employment growth, finding no consistent trade-off between them. We then measure the share of labor costs in the production of garments in the United States and Mexico. We find that the retail price increases necessary to absorb the costs of substantially raising wages are small, well within the range of price increases that polls suggest U.S. consumers are willing to pay. We close by considering some implications of these results.

Identifying “best” applicants in recruiting using data envelopment analysis

Selecting the most promising candidates to fill an open position can be a difficult task when there are many applicants. Each applicant achieves certain performance levels in various categories and the resulting information can be overwhelming. We demonstrate how data envelopment analysis (DEA) can be used as a fair screening and sorting tool to support the candidate selection and decision-making process. Each applicant is viewed as an entity with multiple achievements. Without any a priori preference or information on the multiple achievements, DEA identifies the non-dominated solutions, which, in our case, represent the “best” candidates. A DEA-aided recruiting process was developed that (1) determines the performance levels of the “best” candidates relative to other applicants; (2) evaluates the degree of excellence of “best” candidates’ performance; (3) forms consistent tradeoff information on multiple recruiting criteria among search committee members, and, then, (4) clusters the applicants.

Modeling completeness versus consistency tradeoffs in information decision contexts

Decision makers often confront the issue of whether to utilize information based on incomplete but consistent data or instead rely on complete but less consistent data. For a given decision context, this paper introduces a framework that permits the systematic exploration of this tradeoff between the completeness and consistency of data. The relative weight (importance) of completeness and consistency to the decision maker is an integral component of the approach. To examine the tradeoff, the paper explores in detail various facets of these data quality dimensions. These, in turn, lead to expressions for the measurement of completeness and consistency. The utility of various combinations of completeness and consistency for fixed and variable budgets provides guidance as to the appropriate tradeoff of these factors for specific decision contexts.

On-site economic evaluation of soil conservation practices in Honduras

Abstract Factors affecting the cost to the farmer of employing soil erosion reduction strategies are examined for the steep hillsides near Tegucigalpa, Honduras. Linear programming and MOTAD are used to examine these factors. Results indicate that some modest reductions in erosion can be achieved at little cost to the farmer by reorganizing production, switching rotations, and using contour plowing. These modest reductions still lead to extremely high rates of erosion. Sharper reductions may be achieved at progressively higher costs as erosion control structures are constructed and acreage is left fallow. There is a high cost to the farmer of reducing erosion to ‘sustainable’ levels. A consistent tradeoff emerges between levels of soil conservation, income, and risk; erosion reduction efforts lead to lower incomes and higher risk. The analysis of likely benefits to farmers for erosion reduction shows that even under assumptions of very high yield losses from soil erosion, optimal farm plans still lead to high rates of soil loss, implying a need for policies that internalize externalities if off-farm damages are to be minimized.

On‐site economic evaluation of soil conservation practices in Honduras

AbstractFactors affecting the cost to the farmer of employing soil erosion reduction strategics are examined for the steep hillsides near Tegucigalpa, Honduras. Linear programming and MOTAD are used to examine these factors. Results indicate that some modest reductions in erosion can be achieved at little cost to the farmer by reorganizing production, switching rotations, and using contour plowing. These modest reductions still lead to extremely high rates of erosion. Sharper reductions may be achieved at progressively higher costs as erosion control structures are constructed and acreage is left fallow. There is a high cost to the farmer of reducing erosion to ‘sustainable’ levels. A consistent tradeoff emerges between levels of soil conservation, income, and risk; erosion reduction efforts lead to lower incomes and higher risk. The analysis of likely benefits to farmers for erosion reduction shows that even under assumptions of very high yield losses from soil erosion, optimal farm plans still lead to high rates of soil loss, implying a need for policies that internalize externalities if off‐farm damages are to be minimized.