Data flow analysis of parallel programs

Data flow analysis is the prerequisite of performing optimizations such as common subexpression eliminations or code motion of partial redundant expressions on imperative sequential programs. To apply these transformations to parallel imperative programs, the notion of data flow must be extended to concurrent programs.The additional source language features are: common address space (shared memory), nested parallel statements (PAR),or-parallelism, critical regions and message passing. The underlying interleaving semantics of the concurrently-executed processes result in the so-called state space explosion which on first appearance prevents the computation of the meet over all path solution needed for data flow analysis. For the class of one-bit data flow problems (also known as bit-vector problems) we can show that for the computation of the meet over all path solution, not all interleavings are needed. Based on that, we can give simple data flow equations representing the data flow effects of the PAR statement.The definition of a parallel control flow graph leads to an efficient extension of Killdal\u27s algorithm to compute the data flow of a concurrent program.The time complexity is the same as for analyzing a ``comparable\u27\u27 sequential program

Comparative study on performance accuracy of three probe and five probe flow analysers for wind tunnel testing

In the field of inviscid fluid flow studies, the theoretical concept has to be developed even more. In order to make it possible, it is very important to supplement the concepts with strong experimental results. While performing experimentation, various accepts of design can be determined with factors influencing the and also required modification can be recommended in a more systematic and economic manner. Also, the aim objective of the experiment is to extend the underlying theory and to produce new designs with improvements that can be great support to the advancement in technology. In experimental analysis, wind tunnels are used for the flow analysis over a flying object to be tested. Analyzing the flow plays a predominant role in aerodynamics study. The flow in the test section has to be uniformly streamlined and need to be parallel to the axis of the wind tunnel. The change in flow properties inside the tunnel with respect to the time should be negligible. So, before conducting a test process, calibration of wind tunnel has to be done. Normally, calibration of the subsonic wind tunnel is done by the Pitot static tube. It has the limitations of deprived accuracy and misalignment of the probe with the flow direction. Therefore, new calibrating instruments are proposed by overcoming the limitations of the Pitot static tube. In this paper, experimentation using wind tunnels has been discussed and the truth flow analysis of a low-speed open-circuit wind tunnel has been recorded using two different instruments namely three probe flow analyser and five probe flow analyser respectively. Also, the results obtained have been compared with the data obtained using a pitot static probe

Approaches to High Speed Networks

This work investigates possible methods by which existing potentially available communication bandwidth can be used by communication intensive applications. Presently fiber optic media are available that can provide multiple gigabits of throughput. Unfortunately, because of the computation overhead required to insure that data are reliably transmitted this capacity has not been tapped. A survey of work toward enabling the use of the potential bandwidth is presented. The parallel paradigm is identified as a strong candidate for providing significant increases in system usable bandwidth. Performing communication processing in parallel, however, presents the developer with several implementation options. These options are considered and categorized. This categorization represents a framework that is used in later analysis to compare different approaches and architectures. Because the number of options available represents a combinatorial explosion in the number of software and hardware architectures that could be implemented, a sensitivity analysis is performed to exclude obvious failures, as well as to identify those components that need further study and close consideration. Some components are identified as limiters to total throughput obtainable; these components warrant special attention when implementing a parallel communication system. Building on results obtained through the sensitivity analysis, a testbed was then built and used to obtain performance data for one promising architecture and approach. The results for two and three channels implementations show near linear speedups. These results were then used to verify a model of the system used to calculate throughput values for systems with higher numbers of channels. In order to more fully examine other promising architectures, a simulation program was developed and exercised. The simulation examined the impact of traditional communication parameters, such as window size and timer length, on performance in a parallel system. Further, the simulation confirmed some of the results of the sensitivity analysis and provided insight to the viability of two algorithms to implement flow control in a parallel environment. Additionally, scheduling algorithms to allocate processors to the communication tasks are examined and performance results are presented

Quantum error correction in crossbar architectures

A central challenge for the scaling of quantum computing systems is the need to control all qubits in the system without a large overhead. A solution for this problem in classical computing comes in the form of so called crossbar architectures. Recently we made a proposal for a large scale quantum processor~[Li et al. arXiv:1711.03807 (2017)] to be implemented in silicon quantum dots. This system features a crossbar control architecture which limits parallel single qubit control, but allows the scheme to overcome control scaling issues that form a major hurdle to large scale quantum computing systems. In this work, we develop a language that makes it possible to easily map quantum circuits to crossbar systems, taking into account their architecture and control limitations. Using this language we show how to map well known quantum error correction codes such as the planar surface and color codes in this limited control setting with only a small overhead in time. We analyze the logical error behavior of this surface code mapping for estimated experimental parameters of the crossbar system and conclude that logical error suppression to a level useful for real quantum computation is feasible.Comment: 29 + 9 pages, 13 figures, 9 tables, 8 algorithms and 3 big boxes. Comments are welcom

FloWaveNet : A Generative Flow for Raw Audio

Most modern text-to-speech architectures use a WaveNet vocoder for synthesizing high-fidelity waveform audio, but there have been limitations, such as high inference time, in its practical application due to its ancestral sampling scheme. The recently suggested Parallel WaveNet and ClariNet have achieved real-time audio synthesis capability by incorporating inverse autoregressive flow for parallel sampling. However, these approaches require a two-stage training pipeline with a well-trained teacher network and can only produce natural sound by using probability distillation along with auxiliary loss terms. We propose FloWaveNet, a flow-based generative model for raw audio synthesis. FloWaveNet requires only a single-stage training procedure and a single maximum likelihood loss, without any additional auxiliary terms, and it is inherently parallel due to the characteristics of generative flow. The model can efficiently sample raw audio in real-time, with clarity comparable to previous two-stage parallel models. The code and samples for all models, including our FloWaveNet, are publicly available.Comment: 9 pages, ICML'201

Analysis, Tracing, Characterization and Performance Modeling of Select ASCI Applications for BlueGene/L Using Parallel Discrete Event Simulation

Caltech's Jet Propulsion Laboratory (JPL) and Center for Advanced Computer Architecture (CACR) are conducting application and simulation analyses of Blue Gene/L[1] in order to establish a range of effectiveness of the architecture in performing important classes of computations and to determine the design sensitivity of the global interconnect network in support of real world ASCI application execution

Improving parallel program performance using critical path analysis

A programming tool that performs analysis of critical paths for parallel programs has been developed. This tool determines the critical path for the program as scheduled onto a parallel computer with P processing elements, the critical path for the program expressed as a data flow graph (when maximal parallelism can be expressed), and the minimum number of processing elements (P_opt) needed to obtain maximum program speedup. Experiments were performed using several versions of a Gaussian elimination program to examine how speedup varied with changes in granularity and critical path length. These experiments showed that when the available numer of processing elements P < P_opt, increasing granularity improved program speedup more than reducing (the data flow graph's) critical path length, whereas when P ≥ P_opt, increasing granularity degraded program speedup while reducing critical path length improved program speedup