Modern Fortran in Practice From its earliest days, the Fortran programming language has been designed withcomputingefficiencyinmind.Thelateststandard,Fortran2008,incor- porates a host of modern features, including object-orientation, array opera- tions,user-definedtypes,andprovisionsforparallelcomputing. This tutorial guide shows Fortran programmers how to apply these features intwenty-first-centurystyle:modular,concise,object-oriented,andresource- efficient, using multiple processors. It offers practical real-world examples of interfacingtoC,memorymanagement,graphicsandGUIs,andparallelcom- puting using MPI, OpenMP, and coarrays. The author also analyzes several numerical algorithms and their implementations and illustrates the use of severalopensourcelibraries.Fullsourcecodefortheexamplesisavailableon thebook’swebsite. ArjenMarkusisaseniorconsultantatDeltares,aninstituteforappliedresearch inthefieldofwater,subsurfaceandinfrastructureinTheNetherlands,where hedevelopsandmaintainstheirnumericalmodelingprogramsandthetools that accompany them. He is an active contributor to the ACM newsletter FortranForumandthecomp.lang.fortrannewsgroup. Modern Fortran in Practice Arjen Markus with Foreword by Michael Metcalf cambridgeuniversitypress Cambridge,NewYork,Melbourne,Madrid,CapeTown, Singapore,Sa˜oPaulo,Delhi,MexicoCity CambridgeUniversityPress 32AvenueoftheAmericas,NewYork,NY10013-2473,USA www.cambridge.org Informationonthistitle:www.cambridge.org/9781107603479 (cid:2)c ArjenMarkus2012 Thispublicationisincopyright.Subjecttostatutoryexception andtotheprovisionsofrelevantcollectivelicensingagreements, noreproductionofanypartmaytakeplacewithoutthewritten permissionofCambridgeUniversityPress. Firstpublished2012 PrintedintheUnitedStatesofAmerica AcatalogrecordforthispublicationisavailablefromtheBritishLibrary. LibraryofCongressCataloginginPublicationData Markus,Arjen. ModernFortraninpractice/ArjenMarkus,MichaelMetcalf. pagescm Includesbibliographicalreferencesandindex. ISBN978-1-107-01790-0(hardback)–ISBN978-1-107-60347-9(pbk.) 1.Fortran2008(Computerprogramlanguage) I.Metcalf,Michael. II.Title. QA76.73.F25M375 2012 005.26(cid:2)2–dc23 2012000126 ISBN978-1-107-01790-0Hardback ISBN978-1-107-60347-9Paperback Additionalresourcesforthispublicationathttp://flibs.sf.net/examples-modern-fortran.html CambridgeUniversityPresshasnoresponsibilityforthepersistenceoraccuracyofURLsfor externalorthird-partyInternetwebsitesreferredtointhispublicationanddoesnotguarantee thatanycontentonsuchwebsitesis,orwillremain,accurateorappropriate. "Eademmutataresurgo" (Loosely:thoughchanged,Ireappearasmyself) InscriptiononthegraveofJacobBernoulli, referringtothelogarithmicspiral. Inmemoryofmyfather Myparentstaughtmetobeinquisitive. Mywifeandkidsteachmestillother importantthings. Contents ForewordbyMichaelMetcalf.......................................pagexi Preface..............................................................xv 1. Introduction to Modern Fortran............................ 1 1.1 TheFlavorofModernFortran..................................1 1.2 Fortran90...................................................5 1.3 Fortran95...................................................7 1.4 Fortran2003.................................................8 1.5 Fortran2008.................................................9 1.6 WhatHasNotChanged?.....................................10 2. Array-Valued Functions.................................... 12 2.1 PassingArrays...............................................12 2.2 ElementalFunctionsandAutomaticReallocation................15 2.3 TwoMoreAdvancedExamples................................16 2.4 ConciseStyle................................................20 3. Mathematical Abstractions............................... 21 3.1 AutomaticDifferentiation ....................................21 3.2 IntegerProgramming.........................................26 3.3 EnumeratingSolutionsofDiophantineEquations................28 3.4 DelayedEvaluation..........................................31 4. Memory Management..................................... 35 4.1 FlexibleArrays.............................................. 35 4.2 MemoryLeakswithPointers..................................36 4.3 ExtendinganArray..........................................36 4.4 CharacterStringswithAdjustableLength.......................37 4.5 CombiningAutomaticandAllocatableArrays...................40 4.6 PerformanceofVariousTypesofArrays.........................41 4.7 ParametrizedDerivedTypes...................................42 4.8 AvoidingMemoryLeakswithDerivedTypes....................44 4.9 PerformanceandMemoryAccess..............................48 5. An Interface Problem...................................... 51 5.1 FillingintheParameters......................................52 5.2 UsingaPoolofData.........................................55 vii viii CONTENTS 5.3 PassingExtraArguments......................................60 5.4 ControlStructures...........................................66 5.5 DealingwithDifferentPrecisions..............................73 5.6 Overview...................................................75 6. Interfacing to C:SQLiteAs an Example ................. 76 6.1 MatchingDataTypes........................................76 6.2 PassingArgumentsBetweenCandFortranRoutines.............79 6.3 NamingandCallingConventions..............................80 6.4 DealingwithDerivedTypes...................................82 6.5 InterfacingtoSQLite.........................................85 7. Graphics, GUIs, and the Internet......................... 92 7.1 PlottingtheResults..........................................92 7.2 GraphicalUser-Interfaces.....................................98 7.3 TheInternet...............................................105 7.4 DealingwithXMLFiles.....................................109 8. Unit Testing................................................ 114 8.1 TestingFrameworks.........................................114 8.2 TridiagonalMatricesAsanExample...........................115 8.3 DesignandImplementation ................................. 118 8.4 ConcludingRemarks........................................120 9. Code Reviews............................................. 121 9.1 BeExplicit.................................................121 9.2 Don’tStray................................................125 9.3 AvoidTraps................................................128 9.4 CleanCode................................................132 10. Robust Implementation of Several Simple Algorithms 135 10.1 RelatedApproaches........................................136 10.2 LinearInterpolation.......................................137 10.3 BasicStatistics ............................................143 10.4 FindingtheRootsofanEquation............................151 11. Object-Oriented Programming.......................... 163 11.1 ExtendingTypesandType-BoundProcedures.................163 11.2 InterfacesAsContracts.....................................173 11.3 UsingaPrototypeApproach................................178 11.4 AbstractDataTypesandGenericProgramming ............... 184 11.5 ChangingtheBehaviorofaType............................187 11.6 DesignPatterns...........................................189