recording_backend_mpi – Recording backend mpi - Send data with MPI Description ~~~~~~~~~~~ .. admonition:: 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. There are two ways to set the MPI port. If both are set, option A has precedence 1. The address is supplied via the recording backends “mpi_address” status property. 2. 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) 1) Prepare : Connection of MPI port included in the port_file (see below) 2) Run begin: Send at each beginning of the run (true, 1, CXX_BOOL, 0, 0) 3) Run end : Receive at each ending of the run (true, 1, CXX_BOOL, 0, 0) 4) Run end : Send shape of the data of the run (shape, 1,INT, 0, 0) 5) Run end : Send data of the data of the run (data, shape, DOUBLE, 0, 0) 6) Run end : Send at each ending of the run (true, 1, CXX_BOOL, 0, 1) 7) 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).