Programming

Let’s compare several ways of making Histograms. I’m going to assume you would like to end up with a nice OO histogram interface, so all the 2D methods will fill a Physt histogram. We will be using a 2 x 1,000,000 element array and filling a 2D histogram, or 10,000,000 elements in a 1D histogram. Binnings are regular.

1D 10,000,000 item histogram

2D 1,000,000 item histogram

Let’s try a non-trivial example of a binding: Minuit2 (6.14.0 standalone edition).

This was originally given as a PyHEP 2018 talk. It is designed to be interactive, and can be run in SWAN if you have a CERN account. If you want to run it manually, just download the repository: github.com/henryiii/pybindings_cc. It is easy to run in Anaconda.

CLI11, a powerful library for writing beautiful command line interfaces in C++11, has been updated to 1.6, the largest update ever. CLI11 output is more customizable than ever, and has a better functionality separation under the hood.

CLI11 has had the formatting system completely redesigned, with minor or complete customization of the output possible. Configuration file reading and writing also can be configured; a new example with json instead of ini formatting is included. Validators (finally) have custom help output, as well. Many odd corner cases have been made possible, such as interleaving options.

CMake 3.11 was just released; this is a particularly exciting release for CMake. I’d like to give a quick and friendly introduction to the new features that might make the largest difference for CMake users.

GooFit 2.1 introduces the full-featured Python bindings to GooFit. These bindings mimic the C++ usage of GooFit, including bindings for all PDFs, and also provide NumPy-centric conversions, live Jupyter notebook printing, pip install, and more. Most of the examples in C++ are provided in Python form, as well.

Several other API changes were made. Observables are now distinguished from Variables and provided as a separate class. Both these classes are now passed around by copy everywhere.¹ The three and four body amplitude classes have been refactored and simplified. OpenMP is now supported via homebrew on macOS; GooFit is one of the only packages that currently can build with OpenMP on the default macOS compiler. Eigen is now available, and CLI11 has been updated to version 1.3.

GooFit 2.1 will receive continuing support while development on GooFit 2.2 presses on with a new indexing scheme for PDFs.

Include-what-you-use is a promising little tool for cleaning up a codebase. It didn’t end up working for the use I had for it, but it still could be useful. Here is a quick guideline on installing it on macOS.

CLI11 started years ago as a set of tools built on Boost Program Options (PO), and has since matured into the powerful, easy-to-use stand-alone library it is available today. If you would like to see the original inspiration for CLI11, look at Program.hpp in CLI11 0.1. The rest of the post will focus on a comparison between making a CLI app in the two libraries. I am going to assume that you are preparing fairly basic but non-trivial programs in the following comparison.

TL;DR: CLI11 is more concise, and provides more control with better defaults in many cases, but was inspired by Boost PO.