Shared memory¶

Shared memory is memory that can be accessed by several programs at the same time, enabling them to communicate quickly and avoid redundant copies. Shared memory generally refers to a block of RAM accessible by several cores in a multi-core system. Computers with large amounts of shared memory and many cores per node are well suited for threaded programs, using OpenMP or similar.

Computer clusters built up of many off-the-shelf computers usually have smaller amounts of shared memory and fewer cores per node than custom-built single supercomputers. This means they are more suited for programs using MPI than OpenMP. However, the number of cores per node is going up and many-core chips are now common. This means that OpenMP programs as well as programs combining MPI and OpenMP are often advantageous. §