The CppCon 2015 conference program has been posted for the upcoming September conference. We’ve received requests that the program continue to be posted in “bite-sized” posts, a few sessions at a time, to make the 100+ sessions easier to absorb, so here is another set of talks. This series of posts will conclude once the entire conference program has been posted in this way.

C++ is not composed of only a language. It is also powerful librairies, helping us to get the best fonctionnalities.

The following interrelated CppCon 2015 talks tackle these issues and more (part 2).

In this post:

• Rcpp: Seamless R and C++ Integration
• Mantid, A C++ framework for the reduction and analysis of neutron scattering data
• Integrating generators EDSL's for Boost.Spirit X3
• 3D Face Tracking and Reconstruction using Modern C++
• Using Spirit X3 to Write Parsers
• Boost Units Library for Correct Code

Rcpp: Seamless R and C++ Integration by Matt P. Dziubinski, Assistant Professor, Aalborg University

R is an open-source statistical language designed with a focus on data analysis. While its historical roots are in statistical applications, it is currently experiencing a rapid growth in popularity in all fields where data matters: from data science, through bioinformatics and finance, to machine learning. Key strengths contributing to this growth include its rich libraries ecosystem (over 6 thousands packages at the moment of writing) – often authored by the leading researchers in the field, providing early access to the latest techniques; beautiful, high-quality visualizations – supporting seamless exploratory data analysis and producing stunning presentations; all of this available in an interactive environment resulting in high productivity through fast iteration times.

At the same time, there are no free lunches in programming: the dynamic, interactive nature of R does have its costs, including a significant impact on run-time performance. In an era of growing data sizes and increasingly realistic models this concern is only becoming more important.

In this talk we provide an introduction to Rcpp – a library allowing smooth integration of R with C++, combining the productivity benefits of R for data science together with the performance of C++. First released in 2005, today it’s the most popular language extension for R -- used by over 400 packages. We'll also discuss challenges (as well as possible solutions) involved in integrating modern C++ code, and demonstrate the usage of popular C++ libraries in practice. We’ll conclude the talk with the RInside package allowing to embed R in C++.

Mantid, A C++ framework for the reduction and analysis of neutron scattering data by Steven Hahn, Data Analysis Software Engineer, Oak Ridge National Laboratory

Today one of the most important barriers between performing an experiment and publishing the results is the complex and time-consuming effort that individual researchers apply to data reduction and analysis. In a neutron experiment one must relate measured counts to a physically meaningful four-dimensional scattering function. While the first neutron scatters had to manually setup their instrument and record neutron counts – in handwriting – one single point at a time, users at a modern time of flight spectrometer rapidly collect hundreds of gigabytes of data in less than one day. High performance software is now a necessity. Rapid reduction, analysis and visualization provide feedback for users, helping them make optimal use of limited beam time. Software must also be accessible to and customized by users with a wide range of abilities and interests in programming. In this talk, I will discuss Mantid-(the Manipulation and Analysis Toolkit for Instrument Data), which is the framework designed for the reduction and analysis of data acquired at muon and neutron sources. It is a partnership between multiple user facilities including Rutherford Appleton Laboratory, Oxfordshire, UK, Oak Ridge National Laboratory, Tennessee, USA and the European Spallation Source, Scandinavia. The core of the Mantid Framework is written in C++ with the user interacting via a GUI or python bindings. I will describe real-world cross-platform situations we have encountered while supporting Mantid on Linux, OS X and Windows. This plus a climate that values stability over the latest operating systems and compilers creates challenges to utilizing new language and library features available in C++11/14. To better exploit parallelism on all of the supported platforms, we are wrapping parallel loops so that different implementations can be chosen at compile time. Considerable portions of Mantid provide domain-specific user interfaces to cross-platform libraries. One example is 3D visualization of the large multidimensional datasets generated in Mantid. Our approach utilizes the application widgets and rendering libraries from ParaView. Mantid provides plugins specifically designed for the Mantid data structures. A custom interface for visualization can be started within Mantid, creating a seamless environment for novice users not comfortable with the ParaView workflow.

This research at ORNL’s High Flux Isotope Reactor and Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

Integrating generators EDSL's for Boost.Spirit X3 by Felipe Magno de Almeida, Owner, Expertise Solutions

Based on the presentation I made on C++Now 2015 for Developing EDSL's for Boost.Spirit V2, present the development of generators for Boost.Spirit X3 (next version of boost spirit) and how that can be used for higher abstraction EDSL's while, through template metaprogramming, create parsers and generators automatically from the same grammar, using CORBA format as an example, while dealing with endianness, alignment and asymmetric grammars. This work is based on the library mORBid (https://github.com/expertisesolutions/mORBid) and (https://github.com/expertisesolutions/giop).

3D Face Tracking and Reconstruction using Modern C++ by Patrik Huber, PhD student in computer vision, University of Surrey

In this talk, I will present my work in computer vision, namely landmark detection and 3D face tracking, and the two C++ libraries that were developed in the process. The first part of the talk will give an introduction to detecting facial landmark points and work through a hello-world code example that presents and uses the superviseddescent library, a cross-platform library for cascaded regression that can be used to solve problems like landmark detection or pose estimation. The second part of the talk will present an approach that uses the found landmarks from the first part to use a 3D face model to track a person's face. With the library presented in the process, we hope to make 3D models easier to use and more widespread in the community. Both libraries are designed to be lightweight and simple to use, and try to follow modern C++11/14 programming paradigms. The talk concludes with my views on code sustainability in academia and a wish list of standard library features for computer vision.

Using Spirit X3 to Write Parsers by Michael Caisse, Ciere Consulting

Parsing is a common problem in many domains. The complexity of using a library often pushes developers to ad-hoc solutions utilizing std::string manipulations, regular expressions, or nested if/switch statements. Most “quick hack” implementations are unmaintainable.

Spirit provides a Domain Specific Embedded Language (DSEL) that allows grammars to be described in a natural and declarative manner just like writing PEG or EBNF directly in your C++ code. X3 is the third major release of the Spirit library and improves both compile and run times while simplifying the much of the library.

In this tutorial session you will be introduced to Spirit X3, attribute parsing, and variety of tips to writing efficient and maintainable parsers. We will build a JSON parser during the session to illustrate techniques and usage of the library. This session is applicable toward anyone needing to parse data.

Boost Units Library for Correct Code by Robert Ramey, Proprietor, Robert Ramey Software Development

I will give a presentation on the Boost Units library.

This library implements a zero runtime facility for performing dimensional analysis checking and automatic units conversion on C++ expressions. I have found this indispensable for coding scientific programs involving a variety of complex physical units. The documentation of the Boost Units library is totally complete and accurate, but totally inpenetrable. I had to spend way too much time figuring out how to use this. By attending this meeting, you're going to avoid this pain and just get the benefit of simpler programs that contain fewer bugs.