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1. GNU Make is the de facto standard build tool for software projects developed on and for Linux environments. It relies on a makefile, by default named Makefile, which contains the rules (including the sequence of commands, environment variables, options) that tell Make how to generate an executable from a source code.
2. The configure script is often used to automate the retrieval of system and user information before the compilation and linking steps are performed. It generates a tailored Makefile starting from a general template and the collected information.
3. CMake, not to be confused with GNU Make, is a meta-build tool that uses system-independent and compiler-independent configuration files to generate specific build scripts for a range of system-specific build tools, including GNU Make.

Steps

The process of building software starts with obtaining and unpacking its source code into a directory, which from now on is referred to as $ROOT$ROOTBUILD_DIR.

1. Identify the build process. Usually, the software package provides a detailed description of the build process. Otherwise, you should look for one of the following files indicating which tools are used for the purpose.

   1. A CMakeLists.txt file in the $ROOT$ROOTBUILD_DIR directory indicates a CMake project. Go to step 3.
   2. A configure or configure.sh script in the $ROOT$ROOTBUILD_DIR directory suggests that you must execute a script to configure the build process. Go to step 2.
   3. A Makefile in the $ROOT$ROOTBUILD_DIR directory signals that the project's build process is handled through GNU Make. Go to step 4.

2. configure  scripts. A build process uses a configure script to collect information regarding the environment (operating system, compilers, libraries, etc.) you intend to build the software in. It is able to collect most of the needed information and decide on the best configuration automatically. However, there are few options that you must usually set; for instance, the --prefix option is used to specify the absolute path, the path starting from the root of the filesystem, to the installation directory. There may be options that are not required but desirable in a supercomputing environment, for example, options enabling vectorised instructions. Once the script has run, typically GNU Make must be executed next (step 4).

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   To see the list of all options and arguments, execute the configure script with the –help option,     $ ./configure --help As an example, the following line shows how to run a configure script specifying the --prefix option:     $ ./configure --prefix=/path/to/installation/dir You can also set the value of the environment variables used by the configure script, like this:     $ ./configure VAR=VALUE Expand title List of most common compiling a linking variables Variable Meaning Example CC  C compiler CC=icc  CXX  C++ compiler CXX=icpc  FC Fortran compiler FC=ifort CFLAGS  C compiler flags CFLAGS=-O2  CXXFLAGS  C++ compiler flags CXXFLAGS=-O2 FCFLAGS  Fortran compiler flags FCFLAGS=-O2 CPPFLAGS  C/C++ preprocessor flags CPPFLAGS=-I<include dir> LDDFLAGS  Linker flags LDDFLAGS=-L<library dir> LIBS Linker libraries LIBS=-l<lib name>

   Notes and best practices. Always check the output produced by a configure script. It might contain warnings that call for a modification of the configure options or the shell environment. Some configure scripts compile a test code and execute it, to set some compilation options accordingly. This may not work when compiling in nodes with different architecture from the compute nodes (like the login nodes). For instance, HPE-Cray EX login nodes on Setonix do not have GPU cards nor some of the related libraries, so configure testings may fail. This type of problems can still occur to pure CPU codes. Therefore, we recommend to run the build process on the intended compute nodes for execution (GPU or CPU). If the code is still under development or if the compilation is fast, users can use the development partitions (debug or gpu-dev in the case of Setonix). For long compilations, users should submit the compilation jobs to the "production" partitions (work or gpu in the case of Setonix).

3. Building using CMake. Similarly to configure scripts, CMake generates one or more environment-dependent build files (for Linux-based system they are Makefiles files, covered in step 4) from a high-level, environment-independent definition of the build process that is contained in the CMakeLists.txt file. Terminal 1 shows the typical sequence of commands you should use. Once completed, move to step 4.

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   Code Block language bash theme DJango title Terminal 1. Using CMake to generate build files $ cd $ROOT$ROOTBUILD_DIR $ mkdir build $ cd build $ sg <projectcode> -c 'cmake ..'

   In words,

   1. Change the working directory of the terminal to $ROOT$ROOTBUILD_DIR and create a directory named build (the name can vary, although the one suggested here is standard practice) within the same.

   2. Move Change again the terminal, this time to into the newly created folder.

   3. From the build directory, execute the command cmake passing as an argument the path to the directory containing the CMakeLists.txt file. Typically the relative path .. is used.

   Like the configure script, you can specify options to CMake. The most common one is the CMAKE_INSTALL_PREFIX option that dictates where binaries will be installed (the default location being /usr/local). The syntax for specifying an option to CMake is -DOPTION=Value. In this case, the command would look like this:

       $ cmake -DCMAKE_INSTALL_PREFIX=/path/to/installation/directory ..



4. Building using GNU Make. Conceptually, GNU Make executes commands to compile and link a program specified in the Makefile file, using a dedicated syntax that allows declaring dependencies between the building steps. To launch the build process, change the working directory of the terminal to the one containing the Makefile (that is, $ROOT$ROOTBUILD_DIR) and simply execute the make command. Next, execute the make install command to install the built executable or library.

       $ sg <projectcode> -c 'make'
    $ sg <projectcode> -c 'make install'

   The install argument to make is called target. A target represents a subset of the Makefile file that accomplishes a particular task in the larger context of the build process. In terminal 4, the first make command executes the default target, which usually builds the software without installing it. The install target installs the binaries, that is, the produced executables or libraries.
   Sometimes you must change the value of some variables defined in the Makefile file. Some variable names are standard across most Makefile files. In particular, CC, CXX and FC are used to define executable names for C, C++ and Fortran compilers, respectively, whereas CFLAGS, CXXFLAGS and FFLAGS are used for the corresponding compiling flags.

   All the compiler modules in Pawsey HPC systems define the compiler variables CC, CXX and FC, which are then ready to use by GNU Make.

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