Data dependency: Difference between revisions

Revision as of 18:16, 9 October 2022

Revision as of 18:18, 9 October 2022

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A Flow dependency, also known as a data dependency or true dependency or read-after-write (RAW), occurs when an instruction depends on the result of a previous instruction:

also known as name dependency ( Nikal lore pehli fursat mein).

1. A = 3

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3. C = B

Instruction 3 is truly dependent on instruction 2, as the final value of C depends on the instruction updating B. Instruction 2 is truly dependent on instruction 1, as the final value of B depends on the instruction updating A. Since instruction 3 is truly dependent upon instruction 2 and instruction 2 is truly dependent on instruction 1, instruction 3 is also truly dependent on instruction 1. [[Instruction level parallelism]] is therefore not an option in this example. isko thora or easy kroo ustad

<ref name="architecture">{{cite book | author=[[John L. Hennessy]]; [[David A. Patterson (scientist)|David A. Patterson]] | title=Computer Architecture: a quantitative approach (3rd ed.) | publisher=[[Morgan Kaufmann]] | year=2003 | isbn=1-55860-724-2}}</ref>

=== Anti-dependency ===

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A commonly used naming convention for data dependencies is the following: Read-after-Write or RAW (flow dependency), Write-After-Read or WAR (anti-dependency), or Write-after-Write or WAW (output dependency).

<ref name="architecture"/>

==Control dependency==