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A concurrent programming language is defined as one which uses the concept of simultaneously executing processes or threads of execution as a means of structuring a program. A parallel language is able to express programs that are executable on more than one processor.
However, in multiprocessing systems many processes may run off of, or share, the same reentrant program at the same location in memory, but each process is said to own its own image of the program. Processes are often called "tasks" in embedded operating systems. The sense of "process" (or task) is "something that takes up time", as opposed to ...
Exploitation of the concept of data parallelism started in 1960s with the development of the Solomon machine. [1] The Solomon machine, also called a vector processor, was developed to expedite the performance of mathematical operations by working on a large data array (operating on multiple data in consecutive time steps).
Multiprocessing however means true parallel execution of multiple processes using more than one processor. [7] Multiprocessing doesn't necessarily mean that a single process or task uses more than one processor simultaneously; the term parallel processing is generally used to denote that scenario. [6]
Non-uniform memory access (NUMA) is a computer memory design used in multiprocessing, where the memory access time depends on the memory location relative to the processor. Under NUMA, a processor can access its own local memory faster than non-local memory (memory local to another processor or memory shared between processors). [ 1 ]
In this way, multiple processes are part-way through execution at a single instant, but only one process is being executed at that instant. [citation needed] Concurrent computations may be executed in parallel, [3] [6] for example, by assigning each process to a separate processor or processor core, or distributing a computation across a network.
Switching between threads of a single process can be faster than between two separate processes because threads share the same virtual memory maps, so a TLB flush is not necessary. [ 8 ] The time to switch between two separate processes is called the process switching latency .
Multiprocessor system with a shared memory closely connected to the processors. A symmetric multiprocessing system is a system with centralized shared memory called main memory (MM) operating under a single operating system with two or more homogeneous processors. There are two types of systems: Uniform memory-access (UMA) system; NUMA system