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Stimulation backend mpi - Receive stimulation parameters via MPI¶
Availability
This stimulation backend is only available if NEST was compiled with support for MPI.
The mpi stimulation backend collects data from MPI channels and updates stimulation devices just before each run. This is useful for co-simulation or for receiving stimuli from external software.
The name of the MPI port to receive data on is read from a file for each device configured to use this backend. The file needs to be named according to the following pattern:
{data_path}/{data_prefix}{label}/{node_id}.txt
The data_path
and data_prefix
are global kernel properties,
while label is a property of the device in question and node_id
its node ID. This path can only be set outside of a Run
context
(i.e. after Prepare()
has been called, but Cleanup()
has
not).
Communication Protocol¶
The following protocol is used to exchange information between both MPI processes. The protocol is described using the following format for the MPI messages: (value, number, type, source/destination, tag)
Prepare
: Connection of MPI port include in one file (see below)Run
begin : Send start run (true, 1, CXX_BOOL, 0, 0)Run
begin : Send the id of the device to update (node_id, 1, INT, 0, 0)Run
begin : Receive shape of the data (shape, 1, INT, 0, 0)Run
begin : Receive the data for updating the device (data, shape, DOUBLE, 0, 0)Run
end : Send at each ending of the run (true, 1, CXX_BOOL, 0, 1)Cleanup
: Send at this en of the simulation (true, 1, CXX_BOOL, 0, 2)
Data format¶
The format of the data depends on the exact type of stimulation device.