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Mozilla Research is developing Servo, a parallel web browser engine, to exploit the benefits of parallelism and concurrency in the web rendering pipeline. Parallelization results in improved performance for pinterest.com but not for google.com. This is because the workload of a browser is dependent on the web page it is rendering. In many cases, the overhead of creating, deleting, and coordinating parallel work outweighs any of its benefits. In this paper, we model the relationship between web page primitives and a web browser's parallel performance using supervised learning. We discover a feature space that is representative of the parallelism available in a web page and characterize it using seven key features. Additionally, we consider energy usage trade-offs for different levels of performance improvements using automated labeling algorithms. Such a model allows us to predict the degree of parallelism available in a web page and decide whether or not to render a web page in parallel. This modeling is critical for improving the browser's performance and minimizing its energy usage. We evaluate our model by using Servo's layout stage as a case study. Experiments on a quad-core Intel Ivy Bridge (i7-3615QM) laptop show that we can improve performance and energy usage by up to 94.52% and 46.32% respectively on the 535 web pages considered in this study. Looking forward, we identify opportunities to apply this model to other stages of a browser's architecture as well as other performance- and energy-critical devices., Comment: In Proceedings of the 23rd IEEE International Conference on High Performance Computing, Data, and Analytics (HiPC), Hyderabad, India, December 2016

Data parallelism has proven to be an effective technique for high-level programming of a certain class of parallel applications, but it is not well suited to irregular parallel computations. Blelloch and others proposed nested data parallelism (NDP) as a language mechanism for programming irregular parallel applications in a declarative data-parallel style. The key to this approach is a compiler transformation that flattens the NDP computation and data structures into a form that can be executed efficiently on a wide-vector SIMD architecture. Unfortunately, this technique is ill suited to execution on today's multicore machines. We present a new technique, called data-only flattening , for the compilation of NDP, which is suitable for multicore architectures. Data-only flattening transforms nested data structures in order to expose programs to various optimizations while leaving control structures intact. We present a formal semantics of data-only flattening in a core language with a rewriting system. We demonstrate the effectiveness of this technique in the Parallel ML implementation and we report encouraging experimental results across various benchmark applications.

As energy consumption becomes a first class concern for computing systems, there is an increasing need for application-level access to runtime power/energy measurements. To support this need, a growing number of power and energy monitors are being developed, each with their own interfaces. In fact, the approaches are extremely diverse, and porting energy-aware code to new platforms with new hardware can involve significant rewriting effort. To reduce this effort and support portable, application-level energy monitoring, a common interface is needed. In this paper, we propose EnergyMon, a portable application interface that is independent of underlying power/energy data sources. We demonstrate EnergyMon's flexibility with two case studies -- energy-aware profiling and self-adaptive systems, each of which requires monitoring energy across a range of hardware from different manufacturers. We release the EnergyMon interface, implementations, utilities, and Java and Rust bindings and abstractions as open source.

All modern web browsers --- Internet Explorer, Firefox, Chrome, Opera, and Safari --- have a core rendering engine written in C++. This language choice was made because it affords the systems programmer complete control of the underlying hardware features and memory in use, and it provides a transparent compilation model. Unfortunately, this language is complex (especially to new contributors!), challenging to write correct parallel code in, and highly susceptible to memory safety issues that potentially lead to security holes. Servo is a project started at Mozilla Research to build a new web browser engine that preserves the capabilities of these other browser engines but also both takes advantage of the recent trends in parallel hardware and is more memory-safe. We use a new language, Rust, that provides us a similar level of control of the underlying system to C++ but which statically prevents many memory safety issues and provides direct support for parallelism and concurrency. In this paper, we show how a language with an advanced type system can address many of the most common security issues and software engineering challenges in other browser engines, while still producing code that has the same performance and memory profile. This language is also quite accessible to new open source contributors and employees, even those without a background in C++ or systems programming. We also outline several pitfalls encountered along the way and describe some potential areas for future improvement.

Nested data-parallelism (NDP) is a declarative style for programming irregular parallel applications. NDP languages provide language features favoring the NDP style, efficient compilation of NDP programs, and various common NDP operations like parallel maps, filters, and sum-like reductions. In this paper, we describe the implementation of NDP in Parallel ML (PML), part of the Manticore project. Managing the parallel decomposition of work is one of the main challenges of implementing NDP. If the decomposition creates too many small chunks of work, performance will be eroded by too much parallel overhead. If, on the other hand, there are too few large chunks of work, there will be too much sequential processing and processors will sit idle. Recently the technique of Lazy Binary Splitting was proposed for dynamic parallel decomposition of work on flat arrays, with promising results. We adapt Lazy Binary Splitting to parallel processing of binary trees, which we use to represent parallel arrays in PML. We call our technique Lazy Tree Splitting (LTS). One of its main advantages is its performance robustness: per-program tuning is not required to achieve good performance across varying platforms. We describe LTS-based implementations of standard NDP operations, and we present experimental data demonstrating the scalability of LTS across a range of benchmarks.

Inlining is an optimization that replaces a call to a function with that function's body. This optimization not only reduces the overhead of a function call, but can expose additional optimization opportunities to the compiler, such as removing redundant operations or unused conditional branches. Another optimization, copy propagation, replaces a redundant copy of a still-live variable with the original. Copy propagation can reduce the total number of live variables, reducing register pressure and memory usage, and possibly eliminating redundant memory-to-memory copies. In practice, both of these optimizations are implemented in nearly every modern compiler. These two optimizations are practical to implement and effective in first-order languages, but in languages with lexically-scoped first-class functions (aka, closures), these optimizations are not available to code programmed in a higher-order style. With higher-order functions, the analysis challenge has been that the environment at the call site must be the same as at the closure capture location, up to the free variables, or the meaning of the program may change. Olin Shivers' 1991 dissertation called this family of optimizations superΒ and he proposed one analysis technique, called reflow , to support these optimizations. Unfortunately, reflow has proven too expensive to implement in practice. Because these higher-order optimizations are not available in functional-language compilers, programmers studiously avoid uses of higher-order values that cannot be optimized (particularly in compiler benchmarks). This paper provides the first practical and effective technique for superΒ (higher-order) inlining and copy propagation, which we call unchanged variable analysis. We show that this technique is practical by implementing it in the context of a real compiler for an ML-family language and showing that the required analyses have costs below 3% of the total compilation time. This technique's effectiveness is shown through a set of benchmarks and example programs, where this analysis exposes additional potential optimization sites.

The Manticore project is an effort to design and implement a new functional language for parallel programming. Unlike many earlier parallel languages, Manticore is a heterogeneous language that supports parallelism at multiple levels. Specifically, the Manticore language combines Concurrent ML-style explicit concurrency with fine-grain, implicitly threaded, parallel constructs. These lectures will introduce the Manticore language and explore a variety of programs written to take advantage of heterogeneous parallelism. At the explicit-concurrency level, Manticore supports the creation of distinct threads of control and the coordination of threads through first-class synchronous-message passing. Message-passing synchronization, in contrast to shared-memory synchronization, fits naturally with the functional-programming paradigm. At the implicit-parallelism level, Manticore supports a diverse collection of parallel constructs for different granularities of work. Many of these constructs are inspired by common functional-programming idioms. In addition to describing the basic mechanisms, we will present a number of useful programming techniques that are enabled by these mechanisms.

Compilers for polymorphic languages are required to treat values in programs in an abstract and generic way at the source level. The challenges of optimizing the boxing of raw values, flattening of argument tuples, and raising the arity of functions that handle complex structures to reduce memory usage are old ones, but take on newfound import with processors that have twice as many registers. We present a novel strategy that uses both control-flow and type information to provide an arity raising implementation addressing these problems. This strategy is conservative -- no matter the execution path, the transformed program will not perform extra operations.

A well-adapted visible and infrared spectrograph has been developed for the SNAP (SuperNova/Acceleration Probe) experiment proposed for JDEM. The primary goal of this instrument is to ensure the control of Type Ia supernovae. The spectrograph is also a key element for calibration and is able to measure redshift of some thousands of galaxy spectra both in visible and IR. An instrument based on an integral field method with the powerful concept of imager slicing has been designed and is presented. We present the current design and expected performances. We show that with the current optimization and the proposed technology, we expect the most sensitive instrument proposed on this kind of mission. We recall the readiness of the concept and of the slicer technology thanks to large prototyping efforts performed in France which validate the proposition

Mission requirements, the baseline design, and optical systems budgets for the SuperNova/Acceleration Probe (SNAP) telescope are presented. SNAP is a proposed space-based experiment designed to study dark energy and alternate explanations of the acceleration of the universe’s expansion by performing a series of complementary systematics-controlled astrophysical measurements. The goals of the mission are a Type Ia supernova Hubble diagram and a wide-field weak gravitational lensing survey. A 2m widefield three-mirror telescope feeds a focal plane consisting of 36 CCDs and 36 HgCdTe detectors and a high-efficiency, low resolution integral field spectrograph. Details of the maturing optical system, with emphasis on structural stability during terrestrial testing as well as expected environments during operations at L2 are discussed. The overall stray light mitigation system, including illuminated surfaces and visible objects are also presented.

A well-adapted spectrograph concept has been developed for the SNAP (SuperNova/Acceleration Probe) experiment. The goal is to ensure proper identification of Type Ia supernovae and to standardize the magnitude of each candidate by determining explosion parameters. An instrument based on an integral field method with the powerful concept of imager slicing has been designed and is presented in this paper. The spectrograph concept is optimized to have very high efficiency and low spectral resolution (R {approx} 100), constant through the wavelength range (0.35-1.7{micro}m), adapted to the scientific goals of the mission.

The SuperNova/Acceleration Probe (SNAP) mission will require a two-meter class telescope delivering diffraction limited images spanning a one degree field in the visible and near infrared wavelength regime. This requirement, equivalent to nearly one billion pixel resolution, places stringent demands on its optical system in terms of field flatness, image quality, and freedom from chromatic aberration. We discuss the advantages of annular-field three-mirror anastigmat (TMA) telescopes for applications such as SNAP, and describe the features of the specific optical configuration that we have baselined for the SNAP mission. We discuss the mechanical design and choice of materials for the telescope. Then we present detailed ray traces and diffraction calculations for our baseline optical design. We briefly discuss stray light and tolerance issues, and present a preliminary wavefront error budget for the SNAP Telescope. We conclude by describing some of tasks to be carried out during the upcoming SNAP research and development phase.

The SuperNova / Acceleration Probe (SNAP) is a space-based experiment to measure the expansion history of the Universe and study both its dark energy and the dark matter. The experiment is motivated by the startling discovery that the expansion of the Universe is accelerating. A 0.7 square-degree imager comprised of 36 large format fully-depleted n-type CCD's sharing a focal plane with 36 HgCdTe detectors forms the heart of SNAP, allowing discovery and lightcurve measurements simultaneously for many supernovae. The imager and a high-efficiency low-resolution integral field spectrograph are coupled to a 2-m three mirror anastigmat wide-field telescope, which will be placed in a high-earth orbit. The SNAP mission can obtain high-signal-to-noise calibrated light-curves and spectra for over 2000 Type Ia supernovae at redshifts between z=0.1 and 1.7. The resulting data set can not only determine the amount of dark energy with high precision, but test the nature of the dark energy by examining its equation of state. In particular, dark energy due to a cosmological constant can be differentiated from alternatives such as "quintessence", by measuring the dark energy's equation of state to an accuracy of +/-0.05, and by studying its time dependence., This paper will be published in SPIE Proceedings Vol 4835 and is made available as an electronic preprint with permission of SPIE

The Supernova/Acceleration Probe (SNAP) is a proposed space-borne observatory that will survey the sky with a wide-field optical/near-infrared (NIR) imager. The images produced by SNAP will have an unprecedented combination of depth, solid-angle, angular resolution, and temporal sampling. For 16 months each, two 7.5 square-degree fields will be observed every four days to a magnitude depth of AB=27.7 in each of the SNAP filters, spanning 3500-17000\AA. Co-adding images over all epochs will give AB=30.3 per filter. In addition, a 300 square-degree field will be surveyed to AB=28 per filter, with no repeated temporal sampling. Although the survey strategy is tailored for supernova and weak gravitational lensing observations, the resulting data will support a broad range of auxiliary science programs., Comment: This paper will be published in SPIE Proceedings Vol. 4836 and is made available as an electronic preprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited

B&R Designs began business in the early sixties when Sven Ridder and Lars Bergstrom began sailing after studying aeronautical engineering. The principles learnt during their aeronautical studies were applied to sailboats and the goal, for them, has been to take up the structural loads in the most constructive way. Access to the wind tunnels, test tanks and structural testing facilities at the Royal Institute of Technology in Stockholm enabled them to develop and test many ideas. One of these ideas evolved into the B&R rig. The objective was to develop a rig that was more 'user friendly'. Sailboats, thirty years ago and even today, are often fitted with inner forestays and running backstays requiring careful attention by the crew when tacking or jibing. A rig with less demands was the goal, one that was simpler and any mistakes made when tacking or jibing would not jeopardize the boat or crew. Also a simpler rig would require fewer crew members. Safety was another important consideration - a rig that was simple, easy to manage, suitable for a couple or family for cruising. During this rig development period the first application of the rigid boom vang concept was used on Sven Ridder's own sailboat 'Christina Windex'. Calculations and model testing of rigs were carried out. Optimizing the aerodynamic effect in the most favorable way was a very important aim. A series of wind tunnel tests were done to optimize the shape of mast sections. Because of the low wind speeds over a mast, laminar separation occurs very easily. Air scoops were set up on either side of the mast to achieve an attached flow. The best results occurred with an oval shaped mast section, fitted with a sail groove recessed in a V shaped area at the rear of the mast section.

Extensive and detailed HVDC simulator investigations have been carried out to demonstrate the operating performance of 3-and 4-terminal HVDC systems.