1,537 research outputs found
Recoverable, Abortable, and Adaptive Mutual Exclusion with Sublogarithmic RMR Complexity
We present the first recoverable mutual exclusion (RME) algorithm that is simultaneously abortable, adaptive to point contention, and with sublogarithmic RMR complexity. Our algorithm has O(min(K,log_W N)) RMR passage complexity and O(F + min(K,log_W N)) RMR super-passage complexity, where K is the number of concurrent processes (point contention), W is the size (in bits) of registers, and F is the number of crashes in a super-passage. Under the standard assumption that W = ?(log N), these bounds translate to worst-case O((log N)/(log log N)) passage complexity and O(F + (log N)/(log log N)) super-passage complexity. Our key building blocks are:
- A D-process abortable RME algorithm, for D ? W, with O(1) passage complexity and O(1+F) super-passage complexity. We obtain this algorithm by using the Fetch-And-Add (FAA) primitive, unlike prior work on RME that uses Fetch-And-Store (FAS/SWAP).
- A generic transformation that transforms any abortable RME algorithm with passage complexity of B < W, into an abortable RME lock with passage complexity of O(min(K,B))
Optical map of the genotype A1 WB C6 Giardia lamblia genome isolate
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Molecular and Biochemical Parasitology 180 (2011): 112-114, doi:10.1016/j.molbiopara.2011.07.008.The Giardia lamblia genome consists of 12 Mb divided among 5 chromosomes ranging in size from approximately 1 to 4 Mb. The assembled contigs of the genotype A1 isolate, WB, were previously mapped along the 5 chromosomes on the basis of hybridization of plasmid clones representing the contigs to chromosomes separated by PFGE. In the current report, we have generated an MluI optical map of the WB genome to improve the accuracy of the physical map. This has allowed us to correct several assembly errors and to better define the extent of the subtelomeric regions that are not included in the genome assembly.This work was funded in part by the Woods Hole Center for Oceans and Human Health, jointly funded by the National Science Foundation (OCE-0430724) and the National Institute for Environmental Health Sciences (P50 ES012742)
A Heap-Based Concurrent Priority Queue with Mutable Priorities for Faster Parallel Algorithms
Existing concurrent priority queues do not allow to update the priority of an element after its insertion. As a result, algorithms that need this functionality, such as Dijkstra\u27s single source shortest path algorithm, resort to cumbersome and inefficient workarounds. We report on a heap-based concurrent priority queue which allows to change the priority of an element after its insertion. We show that the enriched interface allows to express Dijkstra\u27s algorithm in a more natural way, and that its implementation, using our concurrent priority queue, outperform existing algorithms
Prefix Siphoning: Exploiting LSM-Tree Range Filters For Information Disclosure (Full Version)
Key-value stores typically leave access control to the systems for which they
act as storage engines. Unfortunately, attackers may circumvent such read
access controls via timing attacks on the key-value store, which use
differences in query response times to glean information about stored data.
To date, key-value store timing attacks have aimed to disclose stored values
and have exploited external mechanisms that can be disabled for protection. In
this paper, we point out that key disclosure is also a security threat -- and
demonstrate key disclosure timing attacks that exploit mechanisms of the
key-value store itself.
We target LSM-tree based key-value stores utilizing range filters, which have
been recently proposed to optimize LSM-tree range queries. We analyze the
impact of the range filters SuRF and prefix Bloom filter on LSM-trees through a
security lens, and show that they enable a key disclosure timing attack, which
we call prefix siphoning. Prefix siphoning successfully leverages benign
queries for non-present keys to identify prefixes of actual keys -- and in some
cases, full keys -- in scenarios where brute force searching for keys (via
exhaustive enumeration or random guesses) is infeasible.Comment: Full version of USENIX ATC'23 pape
Hazma: A Python Toolkit for Studying Indirect Detection of Sub-GeV Dark Matter
With several proposed MeV gamma-ray telescopes on the horizon, it is of
paramount importance to perform accurate calculations of gamma-ray spectra
expected from sub-GeV dark matter annihilation and decay. We present hazma, a
python package for reliably computing these spectra, determining the resulting
constraints from existing gamma-ray data, and prospects for upcoming
telescopes. For high-level analyses, hazma comes with several built-in dark
matter models where the interactions between dark matter and hadrons have been
determined in detail using chiral perturbation theory. Additionally, hazma
provides tools for computing spectra from individual final states with
arbitrary numbers of light leptons and mesons, and for analyzing custom dark
matter models. hazma can also produce electron and positron spectra from dark
matter annihilation, enabling precise derivation of constraints from the cosmic
microwave background.Comment: Minor revisions; fixed typos in FSR spectr
A Feasibility Study of Time-Lapse Seismic Monitoring of CO\u3csub\u3e2\u3c/sub\u3e Sequestration in a Layered Basalt Reservoir
We investigate the potential of scattered seismic waves to remotely sense geological sequestration of CO2 in basalt. Numerical studies in horizontally layered models suggest that strong scattering quickly complicates the wave fields, but also provides a sensitive tool to monitor physical changes in and around the reservoir. These results go hand-in-hand with recent laboratory work and rock-physics modeling that has shown significant changes in the seismic properties of a reservoir undergoing CO2 sequestration, due to fluid substitution and mineral precipitation
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