Parallel computing is a form of computation in which many instructions are carrie out simultaneously, operating on the principle that large problems can often be divided into smaller ones, which are then solved concurrently ("in parallel"). There are several different forms of parallel computing: bit-level parallelism, instruction-level parallelism, data parallelism, and task parallelism. It has been used for many years, mainly in high-performance computing, but interest in it has grown in recent years due to the physical constraints preventing frequency scaling. Parallel computing has become the dominant paradigm in computer architecture, mainly in the form of multicore processors. However, in recent years, power consumption by parallel computers has become a concern.