The Parallel Persistent Memory Model

We consider a parallel computational model that consists of $P$ processors, each with a fast local ephemeral memory of limited size, and sharing a large persistent memory. The model allows for each processor to fault with bounded probability, and possibly restart. On faulting all processor state and local ephemeral memory are lost, but the persistent memory remains. This model is motivated by upcoming non-volatile memories that are as fast as existing random access memory, are accessible at the granularity of cache lines, and have the capability of surviving power outages. It is further motivated by the observation that in large parallel systems, failure of processors and their caches is not unusual. Within the model we develop a framework for developing locality efficient parallel algorithms that are resilient to failures. There are several challenges, including the need to recover from failures, the desire to do this in an asynchronous setting (i.e., not blocking other processors when one fails), and the need for synchronization primitives that are robust to failures. We describe approaches to solve these challenges based on breaking computations into what we call capsules, which have certain properties, and developing a work-stealing scheduler that functions properly within the context of failures. The scheduler guarantees a time bound of $O(W/P_A + D(P/P_A) \lceil\log_{1/f} W\rceil)$ in expectation, where $W$ and $D$ are the work and depth of the computation (in the absence of failures), $P_A$ is the average number of processors available during the computation, and $f \le 1/2$ is the probability that a capsule fails. Within the model and using the proposed methods, we develop efficient algorithms for parallel sorting and other primitives.Comment: This paper is the full version of a paper at SPAA 2018 with the same nam

State-machine replication for planet-scale systems

Online applications now routinely replicate their data at multiple sites around the world. In this paper we present Atlas, the first state-machine replication protocol tailored for such planet-scale systems. Atlas does not rely on a distinguished leader, so clients enjoy the same quality of service independently of their geographical locations. Furthermore, client-perceived latency improves as we add sites closer to clients. To achieve this, Atlas minimizes the size of its quorums using an observation that concurrent data center failures are rare. It also processes a high percentage of accesses in a single round trip, even when these conflict. We experimentally demonstrate that Atlas consistently outperforms state-of-The-Art protocols in planet-scale scenarios. In particular, Atlas is up to two times faster than Flexible Paxos with identical failure assumptions, and more than doubles the performance of Egalitarian Paxos in the YCSB benchmark.H2020 - Horizon 2020 Framework Programme(825184

Digital Signal Processing

Contains a research summary and reports on fifteen research projects.National Science Foundation FellowshipJoint Services Electronics Program (Contract DAAG29-78-C-0020)National Science Foundation (Grant ENG76-24117)U.S. Navy - Office of Naval Research (Contract N00014-75-C-0951)National Science Foundation (Grant ENG76-24117)Schlumberger-Doll Research Center FellowshipHertz Foundation FellowshipNational Aeronautics and Space Administration (Grant NSG-5157)U.S. Navy - Office of Naval Research (Contract N00014-77-C-0196

Digital Signal Processing

Contains research objectives and reports on sixteen research projects.U.S. Navy - Office of Naval Research (Contract N00014-75-C-0852)National Science Foundation FellowshipNational Science Foundation (Grant ENG76-24117)U.S. Navy - Office of Naval Research (Contract N00014-77-C-0257)U.S. Air Force (Contract F19628-80-C-0002)U.S. Navy - Office of Naval Research (Contract N00014-75-C-0951)Schlumberger-Doll Research Center FellowshipHertz Foundation FellowshipGovernment of Pakistan ScholarshipU.S. Navy - Office of Naval Research (Contract N00014-77-C-0196

The shear viscosity of carbon fibre suspension and its application for fibre length measurement

The viscosity of short carbon fibre suspensions in glycerol aqueous solution was measured using a bespoke vane-in-cup viscometer, where the carbon fibre has an aspect ratio from 450 to 2209. In the semi-concentrated regime, nL3 ranging from 20 to 4400, the suspensions demonstrated strong shear-thinning characteristics particularly at higher concentrations. The shear-thinning characteristic is strongly related to the crowding factor proposed by Kerekes, indicating that non-hydrodynamic interactions occur in the suspensions. The influence of fibre bending on viscosity emerges when the bending ratio is lower than 0.0028. An empirical model based on transient network formation and rupture was proposed and used to correlate the relative viscosity with fibre concentration nL3 and shear rate. Based on the model, a viscosity method is established to analyse the fibre length by measuring the viscosity of the fibre suspension using a bespoke vane-in-cup viscometer

Efficient regeneration of in vitro derived plants and genetic fidelity assessment of Phalaenopsis orchid

This study uses inflorescence stalk node as explants to establish an efficient and quick Phalaenopsis orchids cloning procedure for the most significant monopodial orchid in floriculture, without callus formation. The current study aimed to develop a rapid and easy regeneration process utilizing flower stalk nodes as explants, while also evaluating the clonal fidelity of the in vitro micropropagated plants through the analysis of RAPD markers. The tissue-cultured plantlets were grown on a solidified half-strength Murashig and Skoog (MS) base medium enriched with 15% coconut water (CW), 150 mg L−1 activated charcoal, and a mixture of 6-benzylaminopurine, BAP (cytokinins) and α-napthalene acetic acid, NAA and indole 3-butyric acid, IBA (auxins). After 14 weeks of growth, the early production of shoot bud was reported in ½ MS medium enriched with 2.5 mg L−1 BAP alone. Maximum shoot bud multiplication was observed in ½ MS fortified with BAP (2.5 mg L−1) + NAA (1.0 mg L−1), while the lowest was observed in 1.5 mg L−1 BAP + 0.5 mg L−1 IBA after 4 months of culturing. In this investigation, roots emerged simultaneously with shoot elongation from the axil, indicating the absence of a distinct rooting stage. The largest number of roots (3.25) was produced by BAP (2.5 mg L−1) + IBA (1.0 mg L−1) compared to NAA. Control, on the other hand, displayed no signs of root growth. Tissue cultured plantlets with well developed root systems while planted in a potting mixture of brick and charcoal (1: 1) resulted in a 70% survival rate during hardening. The clonal faithfulness of in vitro regenerated crop plantlets to the mother plant was demonstrated by the DNA extraction method with ten micropropagated plants’ young leaves as well as the mother plant using random amplification of a polymorphic DNA marker