MATRIX MULTIPLICATION IN VAX-11

A multidimensional matrix is stored in row order. So a two dimensional N x N matrix will be stored in contiguous memory location where elements are in order:

(0,0), (0,1), …. (0,N-1), (1,0), (1,1), …. (1,N-1), ….. (N-1,0), (N-1,1), …. (N-1, N-1)

For I=0 to N-1 do

begin

for j:=0 to N-1 do

begin

C(I,J):=0

for k:= 0 to N-1 do

C(I,J):=C(I,J) + A(I,k)*B(k,J);

end

end

Assembly Code: R6 : N, R0 : I, R2 : J, R4 : K

R1 : address of C element

R3 : address of A element, value of A

R5 : address of B element

MOVL N, R6

DECL R6

CLRL R0

LOOPI: CLRL R2

LOOPJ: INDEX R2, #0, R6, N, #0, R1

INDEX R0, #0, R6, #1, R1, R1

CLRW C[R1]

CLRL R4

LOOPK: INDEX R4, #0, R6, N, #0, R3

INDEX R0, #0, R6, #1, R3, R3

MOVW A[R3], R3

INDEX R2, #0, R6, N, #0, R5

INDEX R4, #0, R6, #1, R5, R5

MULW2 B[R5]. R3

ADDW2 R3, C[R1]

AOBLSS N, R4, LOOPK

AOBLSS N, R2, LOOPJ

AOBLSS N, R0, LOOPI