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Building the code

Info

See also scram.

Normal build

scram b -j `nproc`

Building for debugging

Whether you prefer debugging with extra verbose messages or by using gdb, those options will help you add extra parameters to scram:

  • For enabling LogDebug messages, run export USER_CXXFLAGS="-DEDM_ML_DEBUG" before running the scram command.
  • For also defining the GPU_DEBUG flag globally (for GPU code), run export USER_CXXFLAGS="-DGPU_DEBUG -DEDM_ML_DEBUG" before running the scram command.
  • For running the code with gdb, you will need to run export USER_CXXFLAGS="-O0 -g" before building.
  • If your debug build is not working, you might need to clean your development area: 
    scram b clean

Rebuilding

If you built CMSSW, changed a file and rebuilt it, some cached object files may still be there. Usually, this should not be a problem, and you should only need to re-run scram b after changing any file.

If you want to be 100% certain that no cached files are used, run scram b clean before re-running scram b.

Multiple jobs

Note that running scram b with multiple jobs launches multiple threads on multiple source files. The compilation order will not be predictable, and the complilation messages will not be predictable.