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Compiling & Building

There are a number of tools to build an application. Very often make or cmake is used to build applications with different complexity.

CMake Explanation

To use Make, you have to manually create the Makefile, but with CMake, the Makefile is automatically created.

Environmental Modules & Makefile

It is quite handy to use environmental modules and load different version of libraries, but how to make use of these ever changing PATHs. Take a look at the following examples to help with making your Makefile ready for modules.

Makefile
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# use the environmental variable $INCLUDE or $CPATH
# split the paths separated by :
INC = $(subst :, ,$(INCLUDE))
INC = $(subst :, ,$(CPATH))
# add a -I/path/to/include
INC := $(INC:%=-I%)
# use the environmental variable $LIBRARY_PATH
LIBS = $(subst :, ,$(LIBRARY_PATH))
LIBS := $(LIBS:%=-L%)

With this code snippet in your Makefile you should be able to use environmental variables such as $INCLUDE/$CPATH or $LIBRARY_PATH efficiently. These paths adapt to your loaded modules.

There is also the possibility to hard code the path of the libraries into the executable.

Makefile
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# use the environmental variable $CPATH
# split the paths separated by :
INC = $(subst :, ,$(CPATH))
# add a -I/path/to/include
INC := $(INC:%=-I%)
# use the environmental variable $LIBRARY_PATH
LIBPATH := $(subst :, ,$(LIBRARY_PATH))
LIBRPATH := $(LIBPATH:%=-Wl,-rpath=%)
LIBPATH := $(LIBPATH:%=-L%)

This allows the user to not load any libraries when running the application, as the path to the libraries is fixed.

Cmake

When using cmake these paths are found automatically.

important is when writing a makefile is to use tabs

Makefile
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target: dependencies
<tab>    command

here is an example of a makefile:

Makefile
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triangle: circle.o age.o
    gfortran circle.o triangle.o -o triangle

triangle.o: triangle.f90
    gfortran -c triangle.f90

circle.o: circle.f90
    gfortran -c circle.f90  

clean:
    rm *.o triangle
running the Makefile
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$ make
gfortran -c circle.f90  
gfortran -c triangle.f90
gfortran circle.o triangle.o -o triangle
$ ./triangle
Enter the radius of the circle:  34
Area of circle with radius   34.00 is      3631.68

or writing a cmake CMakeLists.txt file

CMakeLists.txt
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cmake_minimum_required(VERSION 3.10.0)

enable_language(Fortran)

project (triangle)

add_executable(triangle triangle.f90 circle.f90)

building the application is a bit different

running cmake
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$ mkdir build
$ cd build
$ cmake ...
-- The Fortran compiler identification is GNU 13.2.1
-- Detecting Fortran compiler ABI info
-- Detecting Fortran compiler ABI info - done
-- Check for working Fortran compiler: /usr/bin/f95 - skipped
-- The C compiler identification is GNU 13.2.1
-- The CXX compiler identification is GNU 13.2.1
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done (0.6s)
-- Generating done (0.0s)
-- Build files have been written to: ./Fortran/build
$ make
[ 33%] Building Fortran object CMakeFiles/triangle.dir/circle.f90.o
[ 66%] Building Fortran object CMakeFiles/triangle.dir/triangle.f90.o
[100%] Linking Fortran executable triangle
[100%] Built target triangle
$ ./triangle
Enter the radius of the circle:  34
Area of circle with radius   34.00 is      3631.68