SPMD

In computing, SPMD (single program, multiple data) is a technique employed to achieve parallelism; it is a subcategory of MIMD. Tasks are split up and run simultaneously on multiple processors with different input in order to obtain results faster. SPMD is the most common style of parallel programming. It is also a prerequisite for research concepts such as active messages and distributed shared memory.

In SPMD, multiple autonomous processors simultaneously execute the same program at independent points, rather than in the lockstep that SIMD imposes on different data. With SPMD, tasks can be executed on general purpose CPUs; SIMD requires vector processors to manipulate data streams. Note that the two are not mutually exclusive.

SPMD usually refers to message passing programming on distributed memory computer architectures. A distributed memory computer consists of a collection of independent computers, called nodes. Each node starts its own program and communicates with other nodes by sending and receiving messages, calling send/receive routines for that purpose. Barrier synchronization may also be implemented by messages. The messages can be sent by a number of communication mechanisms, such as TCP/IP over Ethernet, or specialized high-speed interconnects such as Myrinet and Supercomputer Interconnect. Serial sections of the program are implemented by identical computation on all nodes rather than computing the result on one node and sending it to the others.

Nowadays, the programmer is isolated from the details of the message passing by standard interfaces, such as PVM and MPI.

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