We present PowerDial, a system for dynamically adapting application behavior to execute successfully in the face of load and power fluctuations. PowerDial transforms static configuration parameters into dynamic knobs that the PowerDial control system can manipulate to dynamically trade off the accuracy of the computation in return for reductions in the computational resources that the application requires to produce its results. These reductions translate directly into performance improvements and power savings. Our experimental results show that PowerDial can enable our benchmark applications to execute responsively in the face of power caps that would otherwise significantly impair responsiveness. They also show that PowerDial can significantly reduce the number of machines required to service intermittent load spikes, enabling reductions in power and capital costs.

Uncertain data processing is critical in a wide range of applications such as scientific computation handling data with inevitableerrorsandfinancialdecisionmakingrelyingonhuman provided parameters. While increasingly studied in the area of databases, uncertain data processing is often carried out by software, and thus software based solutions are attractive. In particular, Monte Carlo (MC) methods execute software with many samples from the uncertain inputs and observe the statistical behavior of the output. In this paper, we propose a technique to improve the cost-effectiveness of MC methods. Assuming only part of the input is uncertain, the certain part of the input always leads to the same execution across multiple sample runs. We remove such redundancy by coalescing multiple sample runs in a single run. In the coalesced run, the program operates on a vector of values if uncertainty is present and a single value otherwise. We handle cases where control flow and pointers are uncertain. Our results show that we can speed up the execution time of 30 sample runs by an average factor of 2.3 without precision lost or by up to 3.4 with negligible precision lost.

Sampling is a very important and low-cost approach to uncertain data processing, in which output variations caused by input errors are sampled. Traditional methods tend to treat a program as a blackbox. In this paper, we show that through program analysis, we can expose the internals of sample executions so that the process can become more selective and focused. In particular, we develop a sampling runtime that can selectively sample in input error bounds to expose discontinuity in output functions. It identifies all the factors that can potentially lead to the discontinuity and hash the values of such factors in a cost-effective way. The hash values are used to guide the sampling process. We overcome a list of practical challenges, and develop techniques to mitigate the safety issue. Our results show that the technique is very effective for real-world programs. 1.

Sampling is a very important and low-cost approach to uncertain data processing, in which output variations caused by input errors are sampled. Traditional methods tend to treat a program as a blackbox. In this paper, we show that through program analysis, we can expose the internals of sample executions so that the process can become more selective and focused. In particular, we develop a sampling runtime that can selectively sample in input error bounds to expose discontinuity in output functions. It identifies all the program factors that can potentially lead to discontinuity and hash the values of such factors during execution in a cost-effective way. The hash values are used to guide the sampling process. Our results show that the technique is very effective for real-world programs. It can achieve the precision of a high sampling rate with the cost of a lower sampling rate. 1.