G-LOMARC-TS: Lookahead group matchmaking for time/space sharing on multi-core parallel machines

Parallel machines with multi-core nodes are becoming increasingly popular. The performances of applications running on these machines are improved gradually due to the resource competition in each node. Researches have found that coscheduling different applications with complementary resource characteristics on the same set of nodes (semi time sharing) may improve the performance. We propose a scheduling algorithm G-LOMARC-TS which incorporates both space and semi time sharing scheduling methods and matches groups of jobs if possible for coscheduling. Since matchmaking may select jobs further down the waiting queue and the jobs in front of the queue may be delayed subsequently, fairness for each individual job will be watched and the delay will be kept within a limited bound. Several heuristics are used to solve the NP-complete problem of forming groups. Our experiment results show both utilization gain and average relative response time improvements of G-LOMARC-TS over other several scheduling policies

Job Scheduling with Lookahead Group Matchmaking for Time/Space Sharing on Multi-core Parallel Machines

Abstract. Multi-core nodes of parallel machines may only provide gradual performance improvement per application due to competition on resources like the cache. As shown in our earlier work, spreading out applications over as many nodes as possible or letting different applications with potentially complementary characteristics (semi time) share each node by allocating different cores to them may provide better performance. In the latter case, groups of jobs may be necessary to obtain balanced resource utilization due to different sizes of jobs. We present a scheduler G-LOMARC-TS which can match groups of jobs and consider both space-and time-sharing allocation. Since matchmaking may select jobs further down in the waiting queue, fairness in regards to possible delays of the other jobs is watched and delays are kept within certain bounds. This results in a large number of possible combinations. A number of heuristics to select the most promising combinations make it possible to deal with the NP-completeness of the problem. We show that our scheduler improves utilization of high-load phases by about 27% and subsequently average response times by about 36% (and 53% for long jobs) compared to space sharing scheduling for normal workloads. Additionally the scheduler can handle much higher workloads than a space-sharing scheduler

Job Scheduling with Lookahead Group Matchmaking for Time/Space Sharing on Multi-core Parallel Machines

Abstract. Multi-core nodes of parallel machines may only provide gradual performance improvement per application due to competition on resources like the cache. As shown in our earlier work, spreading out applications over as many nodes as possible or letting different applications with potentially complementary characteristics (semi time) share each node by allocating different cores to them may provide better performance. In the latter case, groups of jobs may be necessary to obtain balanced resource utilization due to different sizes of jobs. We present a scheduler G-LOMARC-TS which can match groups of jobs and consider both space- and time-sharing allocation. Since matchmaking may select jobs further down in the waiting queue, fairness in regards to possible delays of the other jobs is watched and delays are kept within certain bounds. This results in a large number of possible combinations. A number of heuristics to select the most promising combinations make it possible to deal with the NP-completeness of the problem. We show that our scheduler improves utilization of high-load phases by about 27% and subsequently average response times by about 36 % (and 53 % for long jobs) compared to space sharing scheduling for normal workloads. Additionally the scheduler can handle much higher workloads than a space-sharing scheduler

Super instrumental El Nio events recorded by a Porites coral from the South China Sea

The 2-7-year periodicities recorded in fossil coral records have been widely used to identify paleo-El Nio events. However, the reliability of this approach in the South China Sea (SCS) has not been assessed in detail. Therefore, this paper presents monthly resolution geochemical records covering the period 1978-2015 obtained from a Porites coral recovered from the SCS to test the reliability of this method. The results suggest that the SCS coral reliably recorded local seawater conditions and the super El Nio events that occurred over the past 3 decades, but does not appear to have been sensitive enough to record all the other El Nios. In detail, the Sr/Ca series distinctly documents only the two super El Nios of 1997-1998 and 2014-2016 as obvious low values, but does not match the Oceanic Nio Index well. The super El Nio of 1982-1983 was identified by the growth hiatus caused by the coral bleaching and subsequent death of the coral. Three distinct stepwise variations occur in the delta C-13 series that are coincident with the three super El Nios, which may be related to a substantial decline in endosymbiotic zooxanthellae density caused by the increase in temperature during an El Nio or the selective utilization of different zooxanthellaes that was required to survive in the extreme environment. The increase in rainfall and temperatures over the SCS during El Nios counteracts the effects on seawater delta O-18 (delta O-18(sw)) and salinity; consequently, coral Delta delta O-18 series can be used as a proxy for delta O-18(sw) and salinity, but are not appropriate for identifying El Nio activity. The findings presented here suggest that the method to identify paleo-El Nio activity based on the 2-7-year periodicities preserved in the SCS coral records might not be reliable, because the SCS is on the edge of El Nio anomalies due to its great distance from the central equatorial Pacific and the imprints of weak and medium strength El Nio events may not be recorded by the corals there

Exploring the temperature dependence of clumped isotopes in modern Porites corals

Porites corals are valuable geological archives for reconstructing past sea surface temperature (SST) in tropical oceans. Their clumped isotope compositions (indicated by Δ values) provide a potential proxy for SST. The Δ value in Porites coral usually departs from thermodynamic equilibrium due to vital effects. To explore the temperature dependence of Δ values in corals, we determined δC, δO, and Δ values in two modern Porites corals from the South China Sea. Our results indicate no intercolony or intracolony biases in Δ values on annual timescales. However, on seasonal timescales, Δ enrichment associated with δC depletion is observed at an intracolony level. This cannot be explained by incomplete hydration and/or hydroxylation of metabolic CO; instead, we interpret this new pattern of isotopic anomalies as a peculiar evidence of vital effects on Δ and δC fractionation. Although complicated by vital effects, the Δ signature in Porites corals still preserved a robust SST dependence, similar to those of recently published Δ-T calibrations. The observed Δ offset relative to inorganic carbonate due to the vital effects is consistent, and relative variations in seasonal SST can be obtained. This study refines the Δ thermometer in Porites corals and strengthens its capacity to be used to reconstruct past SST

An ad hoc routing protocol in hybrid wireless networks for emergency communications

This paper proposes an ad-hoc routing protocol using unicast-based route discovery in a hybrid wireless network, ECCA, which combines ad-hoc networking scheme with a centralized hierarchical network. The network aims to collect damage assessment information in disaster circumstances, maintaining connections between a base station (BS) and nodes by way of multihopping. In the event that a direct link between BS and a node disconnects, the node switches the mode from a cellular to an ad-hoc mode in order to access BS via neighboring nodes. A routing protocol proposed in this paper builds a route by way of monitoring neighbors ' communications instead of broadcasting a route request packet. Experiments show that approximately 90 % of nodes can discover a route within a few hops, even if only 20 % of nodes are able to access BS directly. Even in a low node density, the network is capable of transferring data within three hops. 1