871 research outputs found
Comprehensive characterization of an open source document search engine
This work performs a thorough characterization and analysis of the open source Lucene search library. The article describes in detail the architecture, functionality, and micro-architectural behavior of the search engine, and investigates prominent online document search research issues. In particular, we study how intra-server index partitioning affects the response time and throughput, explore the potential use of low power servers for document search, and examine the sources of performance degradation ands the causes of tail latencies. Some of our main conclusions are the following: (a) intra-server index partitioning can reduce tail latencies but with diminishing benefits as incoming query traffic increases, (b) low power servers given enough partitioning can provide same average and tail response times as conventional high performance servers, (c) index search is a CPU-intensive cache-friendly application, and (d) C-states are the main culprits for performance degradation in document search.Web of Science162art. no. 1
Lifted Successor Generation using Query Optimization Techniques
The standard PDDL language for classical planning uses sev eral first-order features, such as schematic actions. Yet, most classical planners ground this first-order representation into a propositional one as a preprocessing step. While this simpli fies the design of other parts of the planner, in several bench- marks the grounding process causes an exponential blowup that puts otherwise solvable tasks out of reach of the planners. In this work, we take a step towards planning with lifted representations . We tackle the successor generation task, a key operation in forward-search planning, directly on the lifted representation using well-known techniques from database theory . We show how computing the variable substitutions that make an action schema applicable in a given state is essentially a query evaluation problem. Interestingly, a large number of the action schemas in the standard benchmarks result in acyclic conjunctive queries, for which query evaluation is tractable. Our empirical results show that our approach is competitive with the standard (grounded) successor generation techniques in a few domains and outperforms them on benchmarks where grounding is challenging or infeasible
Quantified Constraints in Twenty Seventeen
I present a survey of recent advances in the algorithmic and computational complexity theory of non-Boolean Quantified Constraint Satisfaction Problems, incorporating some more modern research directions
Seeing What You're Told: Sentence-Guided Activity Recognition In Video
We present a system that demonstrates how the compositional structure of
events, in concert with the compositional structure of language, can interplay
with the underlying focusing mechanisms in video action recognition, thereby
providing a medium, not only for top-down and bottom-up integration, but also
for multi-modal integration between vision and language. We show how the roles
played by participants (nouns), their characteristics (adjectives), the actions
performed (verbs), the manner of such actions (adverbs), and changing spatial
relations between participants (prepositions) in the form of whole sentential
descriptions mediated by a grammar, guides the activity-recognition process.
Further, the utility and expressiveness of our framework is demonstrated by
performing three separate tasks in the domain of multi-activity videos:
sentence-guided focus of attention, generation of sentential descriptions of
video, and query-based video search, simply by leveraging the framework in
different manners.Comment: To appear in CVPR 201
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