Parallel computing those that use concurrency, are more difficult to write than sequential ones, because concurrency introduces several new classes of potential software bugs, of which race conditions are the most common. Communication and synchronization between the different subtasks are typically some of the greatest obstacles to getting good parallel program performance. A theoretical upper bound on the speed-up of a single program as a result of parallelization is given by Amdahl's law. Traditionally, computer software has been written for serial computation. To solve a problem, an algorithm is constructed and implemented as a serial stream of instructions. These instructions are executed
Parallel and counter parallel Parallel and counter parallel In music, a parallel chord (relative chord, German: "Parallelklang") is an auxiliary chord derived from one of the primary triads and sharing its function: subdominant parallel, dominant parallel, and tonic parallel. The term is derived from German theory and the writings of Hugo Riemann (see: Riemannian theory). For example, the major and and minor and . The parallel chord (but "not" the counter parallel chord) of a major chord will always be the minor chord whose root is a minor third "down" from the major chord's root, inversely the parallel chord of a minor chord will