Page - 168 - in Programming for Computations – Python - A Gentle Introduction to Numerical Simulations with Python 3.6, Volume Second Edition

168 6 ComputingIntegralsandTestingCode r = sympy.symbols(’r’) I_exact = sympy.integrate(2*sympy.pi*r*r, (r, 0, 2)) print(’Exact integral: {:g}’.format(I_exact.evalf())) x0 = -2; x1 = 2; y0 = -2; y1 = 2 n = 1000 np.random.seed(6) I_expected = 16.7970837117376384 # Computed with this seed I_computed = MonteCarlo_double( lambda x, y: np.sqrt(x**2 + y**2), g, x0, x1, y0, y1, n) print(’MC approximation, {:d} samples: {:.16f}’\ .format(n**2, I_computed)) assert abs(I_expected - I_computed) < 1E-15 (See thefileMC_double.py.) RemarkAboutVersionControlofFiles Havingasuiteof test functionsforautomaticallychecking thatyoursoftware works is considered as a fundamental requirement for reliable computing. Equally important is a system that can keep track of different versionsof the files and the tests, known as a version control system. Today’s most popular version control system is Git,a which the authors strongly recommend the reader to use for programming and writing reports. The combination of Git and cloud storage such as GitHub is a very common way of organizing scientificorengineeringwork.We havea quick introb to Git andGitHub that getsyouupandrunningwithinminutes. The typicalworkflowwithGit goesas follows. 1. Before you start working with files, make sure you have the latest versionof thembyrunninggit pull. 2. Edit files, remove or create files (new files must be registered bygit add). 3. Whenanaturalpieceofwork isdone,commit yourchangesby thegit commitcommand. 4. Implementyourchangesalso in thecloudbydoinggit push. Anice featureofGit is thatpeoplecanedit thesamefileat thesametimeand veryoftenGit will beable toautomaticallymerge the changes(!).Therefore, version control is crucial when you work with others or when you do your work on different types of computers. Another key feature is that anyone can at any time view the history of a file, see who did what when, and roll back theentirefile collection toapreviouscommit.This feature is, of course, fundamentalfor reliablework. a https://en.wikipedia.org/wiki/Git_(software). b http://hplgit.github.io/teamods/bitgit/Langtangen_bitgit-bootstrap.html.