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Loop Interchange

Interchange loop 4-1 and loop 5-1

5-1 DO J = 1, N
4-1   DO I = 1, N
6-1     C(I,J) = 0
      ENDDO
    ENDDO

Vector stride becomes one word!

Interchange loop 5-2 and loop 7-2

5-2 DO J = 1, N
7-2   DO K = 1, N
4-2     DO I = 1, N
8-2       C(I,J)=C(I,J)+A(I,K)*B(K,J)
        ENDDO
      ENDDO
    ENDDO

Type of vector operation is changed!