When writing today's distributed programs, which frequently span both devices and cloud services, programmers are faced with complex decisions and coding tasks around coping with failure, especially when these distributed components are stateful. If their application can be cast as pure data processing, they benefit from the past 40--50 years of work from the database community, which has shown how declarative database systems can completely isolate the developer from the possibility of failure in a performant manner. Unfortunately, while there have been some attempts at bringing similar functionality into the more general distributed programming space, a compelling general-purpose system must handle non-determinism, be performant, support a variety of machine types with varying resiliency goals, and be language agnostic, allowing distributed components written in different languages to communicate. This paper introduces Ambrosia, the first system to satisfy all these requirements. We coin the term "virtual resiliency", analogous to virtual memory, for the platform feature which allows failure oblivious code to run in a failure resilient manner. We also introduce novel programming language constructs for resiliently handling non-determinism. Of further interest is the effective reapplication of much database performance optimization technology to make Ambrosia more performant than many of today's non-resilient cloud solutions.

Computing paths over a terrain that are highly occluded with respect to observers is an important problem in GIS. Given a fast algorithm for computing the visibility map, the path-planning step becomes the bottleneck. In this paper, we present an approach for quickly computing occluded paths over a terrain using a sparse network, a sparse 1-dimensional network over the terrain. We present different strategies for constructing the sparse network. Experimental results show that our approach results in significantly improved time for computing highly occluded paths between two query points, and that the different strategies offer a tradeoff between higher-quality paths and lower preprocessing times. Furthermore, there are strategies that achieve near-optimal paths with small preprocessing cost.

MOTIVATION: High-throughput sequencing of RNA in vivo facilitates many applications, not the least of which is the cataloging of variant splice isoforms of protein-coding messenger RNAs. Although many solutions have been proposed for reconstructing putative isoforms from deep sequencing data, these generally take as their substrate the collective alignment structure of RNA-seq reads and ignore the biological signals present in the actual nucleotide sequence. The majority of these solutions are graph-theoretic, relying on a splice graph representing the splicing patterns and exon expression levels indicated by the spliced-alignment process. RESULTS: We show how to augment splice graphs with additional information reflecting the biology of transcription, splicing and translation, to produce what we call an ORF (open reading frame) graph. We then show how ORF graphs can be used to produce isoform predictions with higher accuracy than current state-of-the-art approaches. AVAILABILITY AND IMPLEMENTATION: RSVP is available as C++ source code under an open-source licence: http://ohlerlab.mdc-berlin.de/software/RSVP/.

Understanding the locations of highly occluded paths on a terrain is an important GIS problem. In this paper we present a model and a fast algorithm for computing highly occluded paths on a terrain. It does not assume the observer locations to be known and yields a path likely to be occluded under a rational observer strategy. We present experimental results that examine several different observer strategies. The repeated visibility map computations necessary for our model is expedited using a fast algorithm for calculating approximate visibility maps that models the decrease in observational fidelity as distance increases. The algorithm computes a multiresolution approximate visibility map and makes use of a graphics processing unit (GPU) to speed up computation. We present experimental results on terrrain data sets with up to 144 million points.