Cloud Index Tracking: Enabling Predictable Costs in Cloud Spot Markets

Cloud spot markets rent VMs for a variable price that is typically much lower than the price of on-demand VMs, which makes them attractive for a wide range of large-scale applications. However, applications that run on spot VMs suffer from cost uncertainty, since spot prices fluctuate, in part, based on supply, demand, or both. The difficulty in predicting spot prices affects users and applications: the former cannot effectively plan their IT expenditures, while the latter cannot infer the availability and performance of spot VMs, which are a function of their variable price. To address the problem, we use properties of cloud infrastructure and workloads to show that prices become more stable and predictable as they are aggregated together. We leverage this observation to define an aggregate index price for spot VMs that serves as a reference for what users should expect to pay. We show that, even when the spot prices for individual VMs are volatile, the index price remains stable and predictable. We then introduce cloud index tracking: a migration policy that tracks the index price to ensure applications running on spot VMs incur a predictable cost by migrating to a new spot VM if the current VM's price significantly deviates from the index price.Comment: ACM Symposium on Cloud Computing 201

Doing More for Our Children: Modeling a Universal Child Allowance or More Generous Child Tax Credit

Child poverty in the United States remains stubbornly high, with 12.2 million children living in poverty in 2013. Nearly 17 percent of children in the United States lived in poverty in 2013 -- a higher rate than for other age groups, and considerably higher than the child poverty rate in other advanced industrialized countries. The U.S. deep child poverty rate -- children who live in families with incomes less than half of the poverty line -- was 4.5 percent of all children in 2013, meaning nearly 1 in 20 children live in families that cannot even afford half of what is considered a minimally adequate living.One key policy for reducing child poverty is the child tax credit (CTC) -- which reduces the child poverty rate from 18.8 percent to 16.5 percent of American children. There is broad acceptance of the importance of the CTC, and key expansions to the CTC were made permanent at the end of 2015. At a moment when leaders ranging from President Barack Obama to Speaker Paul Ryan are talking about poverty, now is an opportune time to explore policy options that would build on this success. This report models two approaches to reduce child poverty in the United States even further -- a universal child allowance and an expanded CTC.A universal child allowance is a cash benefit that is provided to all families with children without regard to their income, earnings, or other qualifying conditions, and that could be subject to taxes for families with high incomes. The U.S. child tax credit, in contrast, is provided only to families that meet a threshold for earnings, phasing in as earnings increase and then phasing out as earnings rise higher. While most other advanced industrialized countries have some kind of universal support for children, the United States does not.For each approach, we begin with a modest reform, and then model increasingly generous versions. In our simulations, we find that even the modest reforms generate important poverty reductions. Our results also make clear that the more we spend on these programs, the greater the reduction in poverty the United States can achieve

The MEarth project: searching for transiting habitable super-Earths around nearby M-dwarfs

Due to their small radii, M-dwarfs are very promising targets to search for transiting super-Earths, with a planet of 2 Earth radii orbiting an M5 dwarf in the habitable zone giving rise to a 0.5% photometric signal, with a period of two weeks. This can be detected from the ground using modest-aperture telescopes by targeting samples of nearby M-dwarfs. Such planets would be very amenable to follow-up studies due to the brightness of the parent stars, and the favourable planet-star flux ratio. MEarth is such a transit survey of ~2000 nearby M-dwarfs. Since the targets are distributed over the entire (Northern) sky, it is necessary to observe them individually, which will be done by using 8 independent 0.4m robotic telescopes, two of which have been in operation since December 2007 at the Fred Lawrence Whipple Observatory (FLWO) located on Mount Hopkins, Arizona. We discuss the survey design and hardware, and report on the current status of the survey, and preliminary results obtained from the commissioning data.Comment: 7 pages, 5 figures. To appear in the Proceedings of the 253rd IAU Symposium: "Transiting Planets", May 2008, Cambridge, M