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SUMMARYLoosely coordinated (implicit/dynamic) coscheduling is a time-sharing approach that originates from network of workstations environments of mixed parallel/serial workloads and limited software support. It is meant to be an easy-to-implement and scalable approach. Considering that the percentage of clusters in parallel computing is increasing and easily portable software is needed, loosely coordinated coscheduling becomes an attractive approach for dedicated machines. Loose coordination offers attractive features as a dynamic approach. Static approaches for local job scheduling assign resources exclusively and non-preemptively. Such approaches still remain beyond the desirable resource utilization and average response times. Conversely, approaches for dynamic scheduling of jobs can preempt resources and/or adapt their allocation. They typically provide better resource utilization and response times. Existing dynamic approaches are full preemption with checkpointing, dynamic adaptation of node/CPU allocation, and time sharing via gang or loosely coordinated coscheduling. This survey presents and compares the different approaches, while particularly focusing on the less well-explored loosely coordinated time sharing. The discussion particularly focuses on the implementation problems, in terms of modification of standard operating systems, the runtime system and the communication libraries.

Navigation is an important aspect in web-site design to make information on web sites easy to find. Different navigation styles have been designed and employed on real-life web pages, most of the styles having good rationales as regards intuitiveness and ease of use. A study based on lay computer users investigates the theory that certain placement/presentation styles for menus are more preferred than others and the expectation that left bars are easiest to use.

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Simultaneous parallel computational grid jobs require reservation by the local job schedulers to ensure allocation of matching time slots at the different sites involved. However, reservations create road blocks in the local schedule, leading to only a small percentage of reservations being tolerable. A large number of reservations typically has adverse effects on local response times and machine utilization. We have extended our SCOJO scheduler to enable advance reservations. SCOJO can perform space sharing or gang scheduling and can run as either adaptive or traditional non-adaptive variant. We show that gang scheduling is more flexible than space sharing in regards to tolerating reservations. We also show that, for space sharing and a low multiprogramming level, the adaptive variants can tolerate reservations better than the non-adaptive variants.