High Performance Software
SHMEM (SHared MEMory)
Unlike with MPI or PVM, SHMEM libraries implement active messaging. The sending of data involves only one CPU in that the source processor simply puts that data into the memory of the destination processor. Likewise, a processor can read data from another processor's memory without interrupting the remote CPU. The remote processor is not made aware that its memory has been read or written unless the programmer implements a mechanism to accomplish this.