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We describe our experience in building a fault-tolerant data-base using the Paxos consensus algorithm. Despite the existing literature in the field, building such a database proved to be non-trivial. We describe selected algorithmic and engineering problems encountered, and the solutions we found for them. Our measurements indicate that we have built a(More)
This paper presents the first analysis of operating system execution on a simultaneous multithreaded (SMT) processor. While SMT has been studied extensively over the past 6 years, previous research has focused entirely on user-mode execution. However, many of the applications most amenable to multithreading technologies spend a significant fraction of their(More)
Although computers continue to improve in speed and functionality, they remain difficult to use. Problems frequently occur, and it is hard to find fixes or workarounds. This paper argues for the importance and feasibility of building a global-scale automated problem diagnosis system that captures the natural, although labor intensive, workflow of system(More)
Several manufacturers have recently announced the first simultaneous-multithreaded processors, both as single CPUs and as components of multi-CPU chips. All are small scale, comprising only two to four thread contexts. A significant impediment to the construction of larger-scale SMTs is the register file size required by a large number of contexts. This(More)
We describe a new class of optimization method based on the theory of alternating projections onto convex sets (POCS). The technique is applied to the problem of intensity modulated beam optimization in conformal radiotherapy. The results of test cases are compared with those from a well established method of simulated annealing. The theory of POCS is due(More)
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