meaning of data flow

1. data flow A data flow architecture or language performs a computation when all the operands are available. Data flow is one kind of data driven architecture, the other is demand driven. It is a technique for specifying parallel computation at a fine-grain level, usually in the form of two-dimensional graphs in which instructions that are available for concurrent execution are written alongside each other while those that must be executed in sequence are written one under the other. Data dependencies between instructions are indicated by directed arcs. Instructions do not reference memory since the data dependence arcs allow data to be transmitted directly from the producing instruction to the consuming one. Data flow schemes differ chiefly in the way that they handle re-entrant code. Static schemes disallow it, dynamic schemes use either "code copying" or "tagging" at every point of reentry. An example of a data flow architecture is MITs VAL machine. data flow analysis A process to discover the dependencies between different data items manipulated by a program. The order of execution in a data driven language is determined solely by the data dependencies. For example, given the equations 1. X = A + B 2. B = 2 + 2 3. A = 3 + 4 a data-flow analysis would find that 2 and 3 must be evaluated before 1. Since there are no data dependencies between 2 and 3, they may be evaluated in any order, including in parallel. This technique is implemented in hardware in some pipelined processors with multiple functional units. It allows instructions to be executed as soon as their inputs are available, independent of the original program order.

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data flow | data flow diagram |

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