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The key '-j4' makes the command use 4 cores in parallel. But you can also run it on one core only with:
make work
4) Modify source code
a) You can find the GEM routines under .../gem/src/*/*, for example :
Most dynamic routines are under:
.../gem/src/gemdyn/base
Most physics routines are under:
.../gem/src/rpnphy/base
Most surface routines are under:
.../gem/src/rpnphy/surface
b) Recreate the executable
Make sure you are in the 'build' directory!
Only if you add any new routines or add include files or module "use" lines to an existing routine you first need to recreate the dependencies and make files by re-executing the full cmake command under point 4d) again.
Otherwise it is enough to just re-execute:
make -j4 work
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