...
Create the directories and the links (using the ${base_dir} from above) :
mkdir -p ${work_space}/${base_dir}/build
mkdir -p ${work_space}/${base_dir}/work
ln -s ${work_space}/${base_dir}/build
ln -s ${work_space}/${base_dir}/work
...
f) Compile and create executable
make -j4 workmaingemdm
The key '-j4' makes the command use 4 cores in parallel. But you can also run it on one core only with:
make workmaingemdm
4) Modify source code
a) You can find the GEM routines under .../gem/src/*/*, for example :
...