Intermediate Modern Fortran

Fortran (a contraction of Formula Translation) was the first programming language to have a standard (in 1954), but has changed significantly over the years. More recent standards (the latest being Fortran 2018) come under the umbrella term "Modern Fortran". Fortran retains very great significance in many areas of scientific and numerical computing, particularly for applications such as quantum chemistry, plasmas, engineering and fluid dynamics, and in numerical weather prediction and climate models.

This intermediate course concentrates on some of the more recent features which are central to Modern Fortran. Attendees should be familiar with the basics of Fortran programming which might be covered in an introductory course, e.g., the one at,

https://github.com/ARCHER2-HPC/archer2-fortran-intro

So, attendees should be comfortable writing structured Fortran programs based on modules and procedures, and have a sound grounding in variables, logic, flow-of-control, and so on. Some knowledge of Fortran I/O is assumed.

There are two main topics in this intermediate course: the facilities in Fortran for abstraction and polymorphism provided by classes and interfaces, and the facilities for formal interoperability with ANSI C. The course will cover type extension ("classes" and "inheritance"), type-bound procedures ("methods"), generic procedures ("polymorphism"), and so on. The standard iso_c_binding module provides facilities for interoperability with C; this allow the communication of Fortran entities with direct analogues C, and also Fortran objects (particularly arrays) which have no direct analogue in C.

Further language features concerning arrays, pointers, and facilities for structured programming using submodules will also be covered along the way.

Knowledge of the object-oriented paradigm would be useful, but is not essential. Knowledge of C is required for the material on C/Fortran interoperation. The course will allow programmers interested in working on larger, structured, software projects to make use of (almost) a full complement of Modern Fortran features.

The course requires a Fortran compiler, for which a local machine or laptop may be appropriate [1]. If you do not have access to a Fortran compiler, course training accounts on ARCHER2 will be available which provide access to various compilers. Use of a text editor will be required (some may prefer an IDE, but we do not intend to consider or support IDEs).

[1] This may typically be gfortran, freely available as part of the GNU Compiler Collection (GCC). See e.g., https://gcc.gnu.org/wiki/GFortranBinaries

Installation

For details of how to log into an ARCHER2 account, see the ARCHER2 Quickstart for users.

Check out the git repository to your laptop or ARCHER2 account.

$ git clone https://github.com/ARCHER2-HPC/archer2-fortran-inter.git

The default Fortran compiler on ARCHER2 is the Cray Fortran compiler invoked using ftn. For example,

$ cd section-1.01
$ ftn example1.f90

should generate an executable with the default name a.out.

Each section of the course is associated with a different directory, each of which contains a number of example programs and exercise templates. Answers to exercises generally re-appear as templates to later exercises. Miscellaneous solutions also appear in the solutions directory.

Not all the examples compile. Some have deliberate errors which will be discussed as part of the course.

Timetable

This is a two-day course.

Day One

Time	Content	Section
09:30	Logistics: login, compiler set-up, local details	None
	See above
10:00	Arrays: recap
	declarations, sections, constructors, allocatable	section-1.01
10:20	Arrays as arguments
	assumed shape, restrictions on arguments, ...	section-1.02
10:40	Pointers and procedures
	pointer, target, contiguous, procedure pointers	section-1.03
11:00	Break
11:30	Derived types
	type, components, assignments and copying	section-2.01
11:50	Interfaces and generic procedures
	interface, operator	section-2.02
12:20	Type extension and polymorphism
	type, extends(...), class	section-2.03
12:40	Type-bound procedures
	contains procedure, pass, generic	section-2.04
13:00	Lunch
14:00	Input/output for types
	write(formatted)	section-3.01
15:00	Break
15:30	Interfaces and abstract types
	type, abstract, deferred	section-4.01
17:00	Close

Day Two

Time	Content	Section
09:30	Submodules
	module, submodule	section-5.01
10:10	Unlimited polymorphic entities
	class (*), typed allocations	section-5.02
11:00	Break
11:30	Type parameters	section-6.01
	kind, len
11:50	Intrinsic modules
	iso_fortran_env, ieee_exceptions, ieee_arithmetic	section-6.02
12:10	Interoperability with C
	iso_c_binding	section-6.03
13:00	Lunch
14:00	...
15:00	Break
15:20	Exercises
15:50	Closing statements
16:00	Close

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