The Significance of  Loop Interchange

• Run time in seconds obtained on an Origin 3000:

• loop order R12K@400MHz

• (8 MB cache)

• i,j,k 535.0

• j,i,k 32.0

• k,j,i 11.0

DO I=1,700

DO J=1,700

DO K=1,700

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

ENDDO ENDDO ENDDO

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