Abstract
By using Dynamic Binary Translation, instruction traces from pre-compiled applications can be offloaded, at runtime, to FPGA-based accelerators, such as Coarse-Grained Loop Accelerators, in a transparent way. However, scheduling onto coarse-grain accelerators is challenging, with two of current known issues being the density of computations that can be mapped, and the effects of memory accesses on performance. Using an in-house framework for analysis of instruction traces, we explore the effect of different window sizes when applying list scheduling, to map the window operations to a coarse-grain loop accelerator model that has been previously experimentally validated. For all window sizes, we vary the number of ALUs and memory ports available in the model, and comment how these parameters affect the resulting latency. For a set of benchmarks taken from the PolyBench suite, compiled for the 32-bit MicroBlaze softcore, we have achieved an average iteration speedup of 5.10x for a basic block repeated 5 times and scheduled with 8 ALUs and memory ports, and an average speedup of 5.46x when not considering resource constraints. We also identify which benchmarks contribute to the difference between these two speedups, and breakdown their limiting factors. Finally, we reflect on the impact memory dependencies have on scheduling.

Abstract
The papers in this special section focus on compiler optimization for FPGA-based systems. Reconfigurable computing (RC) is growing in importance in many computing domains and systems, from embedded, mobile to cloud, and high-performance computing. We have witnessed important advancements regarding the programming of RC-based systems, but further improvements are needed, especially regarding efficient techniques for automatic mapping of computations described in high-level languages to the RC resources. The resources of high-end FPGAs allow these devices to implement complex Systemson-a-Chip (SoCs) and substantial computational components of software applications, e.g., when used as hardware accelerators and/or as more energy-efficient computing platforms. This, however, increases the continuous need for efficient compilers targeting FPGAs, and other RC platforms, from high-level programming languages.

Abstract
Incorporating speed probability distribution to the computation of the route planning in car navigation systems guarantees more accurate and precise responses. In this paper, we propose a novel approach for selecting dynamically the number of samples used for the Monte Carlo simulation to solve the Probabilistic Time-Dependent Routing (PTDR) problem, thus improving the computation efficiency. The proposed method is used to determine in a proactive manner the number of simulations to be done to extract the travel-time estimation for each specific request, while respecting an error threshold as output quality level. The methodology requires a reduced effort on the application development side. We adopted an aspect-oriented programming language (LARA) together with a flexible dynamic autotuning library (mARGOt) respectively to instrument the code and to make decisions on tuning the number of samples to improve the execution efficiency. Experimental results demonstrate that the proposed adaptive approach saves a large fraction of simulations (between 36 and 81 percent) with respect to a static approach, while considering different traffic situations, paths and error requirements. Given the negligible runtime overhead of the proposed approach, the execution-time speedup is between 1.5x and 5.1x. This speedup is reflected at the infrastructure-level in terms of a reduction of 36 percent of the computing resources needed to support the whole navigation pipeline.

Abstract

Abstract
We present VR Designer, a tool for expediting the creation 3D scenes inside VR. It uses controllers and voice commands to create and manipulate primitives and objects imported from openly available repositories. We use modifiers to accelerate repetitive tasks, resorting to procedural content creation techniques to automate the workflow. The tool allows non-expert users to quickly create scenes for contexts such as training or education. We also conducted a user study to validate VR Designer.

Abstract
Immersive Interactive 360° videos, experienced through Head-Mounted Displays (HMD), constitute a particular case of VR applications for which it is relatively easy to record content nowadays, and that can be explored as a game format. We therefore explore the idea of using live action 360° videos as the basis for immersive adventure games. In particular, we explore possible interactions in immersive adventure games based on 360° videos, in terms of game elements and mechanics, and the player's interface with those. To support this, we developed a browser-based framework for creating such games, and conducted a user study with a game created specifically for that purpose. The results obtained indicate a high level of satisfaction with the chosen control schemes and game mechanics, and suggest that the framework can be used to create this kind of experience.