Extending and validating the stencil processing unit

2016 Summer.Includes bibliographical references.Stencils are an important class of programs that appear in the core of many scientific and general-purpose applications. These compute-intensive kernels can benefit heavily from the massive compute power of accelerators like the GPGPU. However, due to the absence of any form of on-chip communication between the coarse-grain processors on a GPU, any data transfer/synchronization between the dependent tiles in stencil computations has to happen through the off-chip (global) memory, which is quite energy-expensive. In the road to exascale computing, energy is becoming an important cost metric. The need for hardware and software that can collaboratively work towards reducing energy consumption of a system is becoming more and more important. To make the execution of dense stencils more energy efficient, Rajopadhye et al. proposed the GPGPU-based accelerator called Stencil Processing Unit that introduces a simple neighbor-to-neighbor communication between the Streaming Multiprocessors (SM) on the GPU, thereby allowing some restricted data sharing between consecutive threadblocks. The SPU includes special storage units, called Communication Buffers, to orchestrate this data transfer and also provides an explicit mechanism for inter-threadblock synchronization by way of a special instruction. It claims to achieve energy-efficiency, compared to GPUs, by reducing the number of off-chip accesses in stencils which in turn reduces the dynamic energy overhead. Uguen developed a cycle-accurate performance simulator for the SPU, called SPU-Sim, and evaluated it using a matrix multiplication kernel which was not suitable for this accelerator. This work focuses on extending the SPU-Sim and evaluating the SPU architecture using a more insightful benchmark. We introduce a producer-consumer based inter-block synchronization approach on the SPU, which is more efficient than the previous global synchronization, and an overlapped multi-pass execution model in the SPU runtime system. These optimizations have been implemented into SPU-Sim. Furthermore, the existing GPUWattch power model in the simulator has been refined to provide better power estimates for the SPU architecture. The improved architecture has been evaluated using a simple 2-D stencil benchmark and we observe an average of 16% savings in dynamic energy on SPU compared to a fairly close GPU platform. Nonetheless, the total energy consumption on SPU is still comparatively high due to the static energy component. This high static energy on SPU is a direct impact of the increased leakage power of the platform resulting from the inclusion of special load/store units. Our conservative estimates indicate that replacing the current design of these L/S units with DMA engines can bring about a 15% decrease in the current leakage power of the SPU and this can help SPU outperform GPU in terms of energy

Fast and accurate determination of the curvature-corrected field emission current

The curvature-corrected field emission current density, obtained by linearizing at or below the Fermi energy, is investigated. Two special cases, corresponding to the peak of the normal energy distribution and the mean normal energy, are considered. It is found that the current density evaluated using the mean normal energy results in errors in the net emission current below 3% for apex radius of curvature, $R_a \geq 5$nm and for apex fields $E_a$ in the range $3-10$ V/nm for an emitter having work-function $\phi = 4.5$eV. An analytical expression for the net field emission current is also obtained for locally parabolic tips using the generalized cosine law. The errors are found to be below 6% for $R_a \geq 5$nm over an identical range of apex field strengths. The benchmark current is obtained by numerically integrating the current density over the emitter surface and the current density itself computed by integrating over the energy states using the exact Gamow factor and the Kemble form for the WKB transmission coefficient. The analytical expression results in a remarkable speed-up in the computation of the net emission current and is especially useful for large area field emitters having tens of thousands of emission sites.Comment: 11 pages, 9 figure

‘Pannirupaattiyal (The Twelve Songs) and the Novel, ‘Prabandha Deepikai’

The life and cultures of human society are of a changing nature from time to time. Literature reflects the cultural norms that prevailed at that time. Grammars are those that characterize literary norms and preserve the richness of language. The separate category of such grammar is the Paattiyal. The earliest of the fully available Paattiyal books by time is the twelve hymns. The three disciplines of epigraphy, terminology, and ethnology consist of 360 volumes. Many Paattiyal books have appeared before this book. None of them are fully available today. The oldest of the texts is the Pannirupaattiyal, the period of which is the tenth century AD. Generally, there are three sections of Paattiyal texts. It is necessary to think about the nature of the compositions, the part that explains the prabandhams, the section on the sequel, the second section that is the grammar of the literary genres, and the nature of the Paattiyal texts

Planning and Implementing a Graduate Online Team Taught Marketing Course

Online courses have become an important educational delivery tool for institutions of higher learning throughout the world. While popular among students and administrators, many faculty members have expressed concerns with online courses. Therefore, this paper highlights online team teaching as a potential solution to concerns harbored by faculty members. In particular, we discuss the planning, coordination, and implementation of a graduate online team taught marketing course and offer an instructional example to alleviate some of the issues with online teaching. Importantly, this paper explores online team teaching from the perspective of marketing faculty and outlines positive educator outcomes associated with the development of a team taught marketing course. This paper illustrates that online team teaching can substantially reduce the concerns harbored by faculty teaching online courses through advanced planning, proper coordination among the faculty members, and input from the involved faculty, administrators and technical staff