Shared State

The shared_state classes are collections to store backend-specific simulator state and can be found in the backend/{multicore, gpu} directories. Functionality manipulating such items gets delegated to the implementations of the shared_state interface.

Ions

Ion state is stored as a series of arrays corresponding to NMODL variables. These arrays have entries per CV and mechanisms need to go through the node_index_ array to map the mechanism’s internal CV index to the cell group’s CV index.

Field	NMODL	Ion Property
iX_	ica	Current density
eX_	eca	Reversal potential
Xi_	cai	Internal concentration
Xo_	cao	External concentration

This table shows the mapping between NMODL – for the ca ion species – and the ion_state members. The class is responsible for resetting currents and concentrations.

Mechanisms

All mechanisms’ private data is stored in shared_state, which is also responsible for managing the lifetime and initialisation of said data. This is done to allow mechanisms to be implemented as essentially stateless bits of C-code interacting with Arbor only through shared_state. See the ABI documentation for a discussion of the details.

Further Functionality

In addition the configuration and effect of stimuli, gap junctions, and sampling, as well as the computation of per-CV time steps is handled here.