Concurrent Processing 2 Final

• the core specification
• mpi doesn't work without it

• an extension to the core spec
• don't need it, but is useful

• Parallel I/O
• C++ binding
• one-sided communications
• dynamic process management

concurrent file access by parallel processes

• remote memory access
• put, get

• allows a process to spawn other processes
• disabled on sharcnet
• available on MPICH2

• not widely implemented
• uses non-blocking collective interfaces

• combined I/O
• separate I/O
• parallel I/O

master slave approach

data-parallel approach

semantically, data parallel approach

• only master deals with file i/o directly
• master passes input data to the slaves
• slaves pass output data back to the master

• only 1 set of input and output files to deal with
• easy port from serial to parallel code
• no issues if nodes use different file systems

performance

each process reads-from or writes-to a separate file

performance

• lots of separate files to manage
• aggregation of results must be handled later

feature of mpi-2 that enables multiple processes of a parallel program to access data from a common file

• #include <mpi.h>
• mpi.lib
• cxx.lib

• treats file like a memory buffer (binary)
• writing is like sending a message
• reading is like receiving a message