Data dependancy in advance computer architecture
Data dependacy:-
The ordering relationship between statement as shown by data dependace. Following are the 5 types of data dependancy/dependance.
(1). Flow dependance (denoted by S1->S2):-
A statement S2 is flow dependant on statement S1. If an execution path is exist from S1 to S2 & if atleast one output of S1 is used as input to S2.
(2). Anti dependance (denoted by S1-|->S2):-
A statement S2 in Anti dependance on statement S1. If S2 follows S1 in program order & if output of S2 overlaps the input S1.
(3). Output dependance(denoted by
S1•->S2):-
Two statements are output dependance if they produces the same output variable.
(4). Input output dependance (I/O->):-
Read & write are I/O statement. Input output dependance occur when same file is referenced by both I/O statement.
(5). Unknown dependance:-
The dependance relationship between two statements can not be determined in the following situations:-
(a). The subscript of a variable is it self subscribed (indirect addressing).
(b). The subscript does not contain the loop index variable.
(c). The subscript is non linear in the loop index variable .
The ordering relationship between statement as shown by data dependace. Following are the 5 types of data dependancy/dependance.
(1). Flow dependance (denoted by S1->S2):-
A statement S2 is flow dependant on statement S1. If an execution path is exist from S1 to S2 & if atleast one output of S1 is used as input to S2.
(2). Anti dependance (denoted by S1-|->S2):-
A statement S2 in Anti dependance on statement S1. If S2 follows S1 in program order & if output of S2 overlaps the input S1.
(3). Output dependance(denoted by
S1•->S2):-
Two statements are output dependance if they produces the same output variable.
(4). Input output dependance (I/O->):-
Read & write are I/O statement. Input output dependance occur when same file is referenced by both I/O statement.
(5). Unknown dependance:-
The dependance relationship between two statements can not be determined in the following situations:-
(a). The subscript of a variable is it self subscribed (indirect addressing).
(b). The subscript does not contain the loop index variable.
(c). The subscript is non linear in the loop index variable .
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