XV Brazilian Symposium on High Performance Computational Systems (WSCAD 2014)

We are very pleased to welcome you to this edition of the Journal of Physics: Conference Series. This is a special issue for WSCAD 2014 (XV Brazilian Symposium on High Performance Computational Systems) which comprises a set of seven papers very carefully selected from the best papers from the WSCAD conference in 2014. The authors of the selected papers submitted an extended version of their work and then all the papers went through a new review process. We are thankful to the authors for their contributions to this special issue.

The first four papers are concerned with the use of accelerators and quantum computing simulation. The first paper is "LALPC: Exploiting Parallelism from FPGAs Using C Language". It presents LALPC, a prototype high-level synthesis tool, specialized for hardware generation for loop-intensive code segments. LALPC extends the functionality of a previous tool by using a subset of the C language as input code to describe computations, improving the usability and potential acceptance of the technique among developers. LALPC also enhances parallelism exploitation by applying loop unrolling, and providing support for automatic generation and scheduling of parallel memory accesses. Next, the second paper "A mechanism to reduce energy waste in the post-execution of GPU applications" is focused on post-execution energy savings. When the post-execution behavior is analyzed in newer GPU ("Graphics Processing Unit") cards, it is observed that the power draw does not return to the idle state in an efficient way, creating an unexpected power wastage. To overcome the power wastage and inefficient returning to idle in the post-execution, the authors developed a strategy to reduce the energy consumption considering a minimal impact on global performance.
The third paper is "Code optimization by using a GPU applied to a Dataflow numerical simulation model". It aims to study techniques for parallel computing using a GPU in order to optimize the performance of a fragment of computational code, implemented as a data-flow system which is part of a meteorological numerical model responsible for calculating the advection transportation phenomena. The possible algorithm limitations for GPU efficiency were also addressed.
The fourth paper is "Optimizing Quantum Simulation for Heterogeneous Computing: a Hadamard Transformation Study". It presents the contributions in the optimization of the environment VirD-GM, conceived in three steps: (i) the theoretical studies and implementation of the abstractions of the Mixed Partial Process defined in the qGM model, focusing on the reduction of the memory consumption regarding multidimensional QTs; (ii) the distributed/parallel implementation of such abstractions allowing its execution on clusters of GPUs; (iii) and optimizations that predict multiplications by zero-value of the quantum states/transformations, implying reduction in the number of computations.
Next, we present the final sequence with three papers focusing on Cloud Computing and Scheduling. The fifth paper is "Middleware for Processing Message Queues with Elasticity Support and Sequential Integrity of Asynchronous Message Processing". It proposes a middleware solution to dynamically analyze the flow of message queues, and a mechanism to increase the parallelized consumption based on the output behavior. An architecture for IOD (Increase On Demand) middleware is presented, with support for the increase and decrease of threads to cope with the growth of message queues, using the technique of limit-based heuristics over a given period of time and grouping messages into sub-queues based on classification criteria.
The sixth paper "Towards Cloud-based Asynchronous Elasticity for Iterative HPC Applications" proposes a PaaS-based model called AutoElastics aimed at providing cloud elasticity for HPC applications in an efficient and transparent manner. In particularl, AutoElastic is focusing on master-slave iterative applications, but offers a flexible framework to support other HPC programming styles, such as pipeline and BSP.
Finally, the paper "ComprehensiveBench: a Benchmark for the Extensive Evaluation of Global Scheduling Algorithms" presents a benchmark for global scheduling algorithms that enables the variation of a vast range of parameters that affect performance. ComprehensiveBench can be used to assist in the development and evaluation of new scheduling algorithms, to help choose a specific algorithm for an arbitrary application, to emulate other applications, and to enable statistical tests.
The guest editors would like to thank all the program committee members, session chairs and the audience of the WSCAD 2014 for their work and participation. We also would like to thank the editors of the JPCS for the opportunity, the Editorial Board members and especially the journal invited reviewers, for their important collaboration, reviewing the final papers that allowed this special issue become a reality.