Abstract-Embedded DSP computing is currently shifting towards manycore architectures in order to cope with the ever growing computational demands. Actor based dataflow languages are being considered as a programming model. In this paper we present a code generator for CAL, one such dataflow language.We propose to use a compilation tool with two intermediate representations. We start from a machine model of the actors that provides an ordering for testing of conditions and firing of actions. We then generate an Action Execution Intermediate Representation that is closer to a sequential imperative language like C and Java. We describe our two intermediate representations and show the feasibility and portability of our approach by compiling a CAL implementation of the Two-Dimensional Inverse Discrete Cosine Transform on a general purpose processor, on the Epiphany manycore architecture and on the Ambric massively parallel processor array.

Today computer architectures are shifting from single core to manycores due to several reasons such as performance demands, power and heat limitations. However, shifting to manycores results in additional complexities, especially with regard to efficient development of applications. Hence there is a need to raise the abstraction level of development techniques for the manycores while exposing the inherent parallelism in the applications. One promising class of programming languages is dataflow languages and in this paper we evaluate and optimize the code generation for one such language, CAL. We have also developed a communication library to support the intercore communication. The code generation can target multiple architectures, but the results presented in this paper is focused on Adapteva's many core architecture Epiphany. We use the twodimensional inverse discrete cosine transform (2D-IDCT) as our benchmark and compare our code generation from CAL with a hand-written implementation developed in C. Several optimizations in the code generation as well as in the communication library are described, and we have observed that the most critical optimization is reducing the number of external memory accesses. Combining all optimizations we have been able to reduce the difference in execution time between auto-generated and handwritten implementations from a factor of 4.3x down to a factor of only 1.3x.

While parallel computer architectures have become mainstream, application development on them is still challenging. There is a need for new tools, languages and programming models. Additionally, there is a lack of knowledge about the performance of parallel approaches of basic but important operations, such as the QR decomposition of a matrix, on current commercial manycore architectures. This paper evaluates a high level dataflow language (CAL), a source-to-source compiler (Cal2Many) and three QR decomposition algorithms (Givens Rotations, Householder and Gram-Schmidt). The algorithms are implemented both in CAL and hand-optimized C languages, executed on Adapteva's Epiphany manycore architecture and evaluated with respect to performance, scalability and development effort.The performance of the CAL (generated C) implementations gets as good as 2% slower than the hand-written versions. They require an average of 25% fewer lines of source code without significantly increasing the binary size. Development effort is reduced and debugging is significantly simplified. The implementations executed on Epiphany cores outperform the GNU scientific library on the host ARM processor of the Parallella board by up to 30x.

Abstract-With the advent of manycore architectures comprising hundreds of processing elements, fault management has become a major challenge. We present an approach that uses the occam-pi language to manage the fault recovery mechanism on a new manycore architecture, the Platform 2012 (P2012). The approach is made possible by extending our previously developed compiler framework to compile occam-pi implementations to the P2012 architecture. We describe the techniques used to translate the salient features of the occam-pi language to the native programming model of the P2012 architecture. We demonstrate the applicability of the approach by an experimental case study, in which the DCT algorithm is implemented on a set of four processing elements. During runtime, some of the tasks are then relocated from assumed faulty processing elements to the faultless ones by means of dynamic reconfiguration of the hardware. The working of the demonstrator and the simulation results illustrate not only the feasibility of the approach but also how the use of higher-level abstractions simplifies the fault handling.

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