Cooperating runtime systems in LiPS

Performing computation using networks of workstations is increasingly becoming an alternative to using a supercomputer. This approach is motivated by the vast quantities of unused idle-time available in workstation networks. Unlike comptuting o a tighty coupled parallel computer, where a fixed number of processor nodes is used within a computation, the number of usable nodes in a workstation network is constantly changing over time. Additionally, workstations are more frequently subject to outages, e.g. due to reboots. The question arises how applications, adapting smoothly to this environment, should be realized. LiPS is a system for distributed computing using idle-cycles in networks for workstations. This system is ints version 2.3 is currently used at the Universität des Saarlandes in Saarbrücken, Germany to perform computationally intensive applications in the field of cryptography on a net of approximately 250 workstations and should be enhanced to work within an environment of more than 1000 machines all over the world within the next years. In this paper we present the runtime systems of LiPS along with performance measurements taken with the current LiPS development version 2.4

Software fault-tolerant distributed applications in LiPS

This paper illustrates how software fault-tolerant distributed applications are implemented within LIPS version 2.4, a system for distributed computing using idle-cycles in networks of workstations. The LIPS system [SR92, SR93,STea94,Set95,SF96,ST96,SL97,Set97] employs the tuple space programming paradigm, as originally used in the LINDA programming language. Applications implemented using this paradigm easily adapt to changes in availability as they occur in workstation networks. In LIPS, applications are enabled to terminate successfully in spite of failing nodes by periodically writing checkpoints, freezing the state of a computational process, and keeping track of messages exchanged between checkpoints in a message log. The message log is kept within the tuple space machine implementing the tuple space and replayed if an application process recovers. This assumes deterministic behavior of the application process but allows independent checkpoint generation and alleviates the need for application-wide synchronization in order to generate sets of consistent checkpoints

Cooperating runtime systems in LiPS

Performing computation using networks of workstations is increasingly becoming an alternative to using a supercomputer. This approach is motivated by the vast quantities of unused idle-time available in workstation networks. Unlike comptuting o a tighty coupled parallel computer, where a fixed number of processor nodes is used within a computation, the number of usable nodes in a workstation network is constantly changing over time. Additionally, workstations are more frequently subject to outages, e.g. due to reboots. The question arises how applications, adapting smoothly to this environment, should be realized. LiPS is a system for distributed computing using idle-cycles in networks for workstations. This system is ints version 2.3 is currently used at the Universität des Saarlandes in Saarbrücken, Germany to perform computationally intensive applications in the field of cryptography on a net of approximately 250 workstations and should be enhanced to work within an environment of more than 1000 machines all over the world within the next years. In this paper we present the runtime systems of LiPS along with performance measurements taken with the current LiPS development version 2.4

LiPS : a system for distributed processing on workstations

sc LiPS (sc Library for sc Parallel sc Systems) is a collection of C functions enabling a programmer to distribute applications with low communication granularity over a network of UNIX workstations. sc LiPS restricts its applications to the use of idle time. As the potential computing power, arising from wasted time slices (idle-time) of workstations, often overwhelms even the power of supercomputers, sc LiPS is a cheap alternative to solve computing intensive problems. Based on UNIX, using socket communication primitives sc LiPS was developed on a network of workstations running the UNIX Operating system. The present release (2.1) is used at the Department of Computer Science at the University of the Saarland. With about 150 machines we reach a total computing power of about 2500 MIPS.

Terrestrial behavior in titi monkeys (Callicebus, Cheracebus, and Plecturocebus) : potential correlates, patterns, and differences between genera

For arboreal primates, ground use may increase dispersal opportunities, tolerance to habitat change, access to ground-based resources, and resilience to human disturbances, and so has conservation implications. We collated published and unpublished data from 86 studies across 65 localities to assess titi monkey (Callicebinae) terrestriality. We examined whether the frequency of terrestrial activity correlated with study duration (a proxy for sampling effort), rainfall level (a proxy for food availability seasonality), and forest height (a proxy for vertical niche dimension). Terrestrial activity was recorded frequently for Callicebus and Plecturocebus spp., but rarely for Cheracebus spp. Terrestrial resting, anti-predator behavior, geophagy, and playing frequencies in Callicebus and Plecturocebus spp., but feeding and moving differed. Callicebus spp. often ate or searched for new leaves terrestrially. Plecturocebus spp. descended primarily to ingest terrestrial invertebrates and soil. Study duration correlated positively and rainfall level negatively with terrestrial activity. Though differences in sampling effort and methods limited comparisons and interpretation, overall, titi monkeys commonly engaged in a variety of terrestrial activities. Terrestrial behavior in Callicebus and Plecturocebus capacities may bolster resistance to habitat fragmentation. However, it is uncertain if the low frequency of terrestriality recorded for Cheracebus spp. is a genus-specific trait associated with a more basal phylogenetic position, or because studies of this genus occurred in pristine habitats. Observations of terrestrial behavior increased with increasing sampling effort and decreasing food availability. Overall, we found a high frequency of terrestrial behavior in titi monkeys, unlike that observed in other pitheciids