Array Padding: Example

COMMON // A(1024,1024),

B(1024,1024),

C(1024,1024)

DO J=1,1024

DO I=1,1024

A(I,J) = A(I,J)+B(I,J)*C(I,J)

ENDDO ENDDO

Addr[C(1,1)] = Addr[B(1,1)] + 1024*1024*4

position in the cache: C(1,1) = B(1,1) since (1024*1024*4) mod 32KB = 0

COMMON // A(1024,1024),pad1(129)

B(1024,1024),pad2(129)

C(1024,1024)

DO J=1,1024

DO I=1,1024

A(I,J) = A(I,J)+B(I,J)*C(I,J)

ENDDO ENDDO

Addr[C(1,1)] = Addr[B(1,1)] + 1024*1024*4+129*4

position in the cache: C(1,1) = B(129,1) mod 32KB

Padding will cause cache lines

to be placed in different

cache locations

Compiler will try to do padding

automatically

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