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The following exercises will help you understand how to build your own software on the ATOS HPCF or ECS.

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Before we start...

1. Ensure your environment is clean by running:

   No Format
   module reset

   
   

2. Create a directory for this tutorial and cd into it:

   No Format
   mkdir -p compiling_tutorial cd compiling_tutorial

   
   

Building simple programs

1. With your favourite editor, create three hello world programs, one in C, one in C++ and one in Fortran

   Code Block
   language cpp title hello.c collapse true
   #include <stdio.h> int main(int argc, char** argv) { printf("Hello World from a C program\n"); return 0; }

   
   

   Code Block
   language cpp title hello++.cc collapse true
   #include <iostream> int main() { std::cout << "Hello World from a C++ program!" << std::endl; }

   
   

   Code Block
   language cpp title hellof.f90 collapse true
   program hello print *, "Hello World from a Fortran Program!" end program hello

   
   

2. Compile and run each one of them with the GNU compilers (gcc, g++, gfortran)

   Expand
   title Solution
   We can build them with: No Format gcc -o hello hello.c g++ -o hello++ hello++.cc gfortran -o hellof hellof.f90 All going well, we should have now the executables that we can run No Format $ for exe in hello hello++ hellof; do ./$exe; done Hello World from a C program Hello World from a C++ program! Hello World from a Fortran Program!

   
   

3. Now, use the generic environment variables for the different compilers ($CC, $CXX, $FC) and rerun, you should see no difference to the above results.

   Expand
   title Solution
   We can rebuild them with: No Format $CC -o hello hello.c $CXX -o hello++ hello++.cc $FC -o hellof hellof.f90 We can now run them exactly in the same way: No Format $ for exe in hello hello++ hellof; do ./$exe; done Hello World from a C program Hello World from a C++ program! Hello World from a Fortran Program! Tip title Always use the environment variables for compilers We always recommend using the environment variables since it will make it easier for you to switch to a different compiler.

   
   

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