Internet based volunteer computing projects such as SETI@home are currently restricted to performing coarse grained, embarrassingly parallel tasks. This is partly due to the "pull" nature of task distribution in volunteer computing environments, where workers request tasks from the master rather than the master assigning tasks to arbitrary workers. In this paper we develop algorithms for computing batches of medium grained tasks with soft deadlines in pull-style volunteer computing environments. Using assumptions about worker availability intervals based on previous studies, we develop models of unreliable workers in volunteer computing environments. These models are used to develop algorithms for task distribution in volunteer computing systems with a high probability of meeting batch deadlines. We develop algorithms for perfectly reliable workers, computation-reliable workers and unreliable workers. The effectiveness of the algorithms is demonstrated by using traces from actual execution environments.
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