Using GPU to Accelerate Linear Computations in Power System Applications

With the development of advanced power system controls, the industrial and research community is becoming more interested in simulating larger interconnected power grids. It is always critical to incorporate advanced computing technologies to accelerate these power system computations. Power flow, one of the most fundamental computations in power system analysis, converts the solution of non-linear systems to that of a set of linear systems via the Newton method or one of its variants. An efficient solution to these linear equations is the key to improving the performance of power flow computation, and hence to accelerating other power system applications based on power flow computation, such as optimal power flow, contingency analysis, etc. This dissertation focuses on the exploration of iterative linear solvers and applicable preconditioners, with graphic processing unit (GPU) implementations to achieve performance improvement on the linear computations in power flow computations. An iterative conjugate gradient solver with Chebyshev preconditioner is studied first, and then the preconditioner is extended to a two-step preconditioner. At last, the conjugate gradient solver and the two-step preconditioner are integrated with MATPOWER to solve the practical fast decoupled load flow (FDPF), and an inexact linear solution method is proposed to further save the runtime of FDPF. Performance improvement is reported by applying these methods and GPU-implementation. The final complete GPU-based FDPF with inexact linear solving can achieve nearly 3x performance improvement over the MATPOWER implementation for a test system with 11,624 buses. A supporting study including a quick estimation of the largest eigenvalue of the linear system which is required by the Chebyshev preconditioner is presented as well. This dissertation demonstrates the potential of using GPU with scalable methods in power flow computation

Efficient fault tolerance for selected scientific computing algorithms on heterogeneous and approximate computer architectures

Scientific computing and simulation technology play an essential role to solve central challenges in science and engineering. The high computational power of heterogeneous computer architectures allows to accelerate applications in these domains, which are often dominated by compute-intensive mathematical tasks. Scientific, economic and political decision processes increasingly rely on such applications and therefore induce a strong demand to compute correct and trustworthy results. However, the continued semiconductor technology scaling increasingly imposes serious threats to the reliability and efficiency of upcoming devices. Different reliability threats can cause crashes or erroneous results without indication. Software-based fault tolerance techniques can protect algorithmic tasks by adding appropriate operations to detect and correct errors at runtime. Major challenges are induced by the runtime overhead of such operations and by rounding errors in floating-point arithmetic that can cause false positives. The end of Dennard scaling induces central challenges to further increase the compute efficiency between semiconductor technology generations. Approximate computing exploits the inherent error resilience of different applications to achieve efficiency gains with respect to, for instance, power, energy, and execution times. However, scientific applications often induce strict accuracy requirements which require careful utilization of approximation techniques. This thesis provides fault tolerance and approximate computing methods that enable the reliable and efficient execution of linear algebra operations and Conjugate Gradient solvers using heterogeneous and approximate computer architectures. The presented fault tolerance techniques detect and correct errors at runtime with low runtime overhead and high error coverage. At the same time, these fault tolerance techniques are exploited to enable the execution of the Conjugate Gradient solvers on approximate hardware by monitoring the underlying error resilience while adjusting the approximation error accordingly. Besides, parameter evaluation and estimation methods are presented that determine the computational efficiency of application executions on approximate hardware. An extensive experimental evaluation shows the efficiency and efficacy of the presented methods with respect to the runtime overhead to detect and correct errors, the error coverage as well as the achieved energy reduction in executing the Conjugate Gradient solvers on approximate hardware