# Homework Solution: Do these subroutines multiply Ax by rows or columns? Start with B(I) = 0: DO 10 I = 1, N DO 10 J = 1, N DO 10 J = 1, N Do… Do these subroutines multiply Ax by rows or columns? Start with B(I) = 0: DO 10 I = 1, N DO 10 J = 1, N DO 10 J = 1, N Do 10 I = 1, N B(I) = B(I) + A(I, J) * X(J) B(I) = B(I) +A (I, J) X (J) The outputs Bx = Ax are the same. The second code is slightly more efficient in FORTRAN and much more efficient on a vector machine (the first changes single entries B(I), the second can update whole vectors).

A(I, J) * X(J) That means I = 1 to N then J=1 to N Do these subroutines enlarge Ax by rows or columns? Start with B(I) = 0: DO 10 I = 1, N DO 10 J = 1, N DO 10 J = 1, N Do 10 I = 1, N B(I) = B(I) + A(I, J) * X(J) B(I) = B(I) +A (I, J) X (J) The outputs Bx = Ax are the similar. The remedy regulation is partially further prolific in FORTRAN and abundantly further prolific on a vector deed (the earliest changes only entries B(I), the remedy can update entire vectors).