Auryn classes use the following global variables (as of Auryn v0.8.0) which are initialized by the auryn_init() function.

In auryn_global.h

extern System * sys;
extern Logger * logger;

Are references to the Auryn kernel (sys) and the global logger.

extern mpi::environment * mpienv;
extern mpi::communicator * mpicommunicator;

References required by Boost MPI. These variables are not declared when Auryn is compiled without MPI support.

In auryn_definitions.h:

extern double auryn_timestep; 

Defines the Auryn simulation time step in seconds has to be set/changed before auryn_init() is called. The default time step is 1e-4 (0.1ms). auryn_timestep was formally called dt in older versions.