Data dependency

Data dependency (data dependency ) describes the situation in computer science, that data is used by an instruction, are also used by a previous instruction.

A distinction is made between the following types of data dependencies:

  • True data dependency (true dependence, read- after-write ) is when a statement read-accesses the result of a preceding statement. example: a = b c
  • D = a 1
  • Counter- dependence ( anti- dependence, write -after- read) is when a statement writes a value (over), is used to read in the foregoing statement on the. example: a = b c
  • B = d 1
  • Output dependence (output dependence, write -after- write) is when both instructions write to the same variable. example: a = b c
  • A = d e

If - as in conventional programs - but a statement after the other runs, represent data dependencies not a problem For processors with pipelining that perform multiple instructions in parallel, they can lead to data conflicts.

Hazard (computer architecture) John L. Hennessy David Patterson (computer scientist)
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