Warning
This version of the documentation is NOT an official release. You are looking at ‘latest’, which is in active and ongoing development. You can change versions on the bottom left of the screen.
Recording backend mpi - Send data with MPI¶
Description¶
Availability
This stimulation backend is only available if NEST was compiled with support for MPI.
The mpi recording backend sends collected data to a remote process using MPI.
The name of the MPI port to send data to 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 included in the port_file (see below)Run
begin: Send at each beginning of the run (true, 1, CXX_BOOL, 0, 0)Run
end : Receive at each ending of the run (true, 1, CXX_BOOL, 0, 0)Run
end : Send shape of the data of the run (shape, 1,INT, 0, 0)Run
end : Send data of the data of the run (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 sent is an array consisting of (id device, id node, time is ms).