Mips function array

Question

I am a attempting to create a function that arranges the of numbers in a square grid, where the numbers in each row, each column, and the numbers in the forward and backward main diagonals, all add up to the same number. And while I am relatively new to mips here is my latest attempt:

square:  lw $t0,$zero #i = 0
     lw $t2,1 # k = 1
     div $t1,$a1,2 # j = n/2
     mul $t3,$a1,$a1 #  n*n

while:  ble $t2,$t3,else1 # k <= n*n
    bgt $t0,-1,else2 #
    bgt $t1,-1,else2 #
    ble $t1,$a1,else3 #
    ble $t0,$a1,else4 #
    bne $,$,else5#a[i,j] == 0

else1:  #a[i,j] = k
    addi $t0,$t0,-1 #
    addi $t1,$t1,1 #
    addi $t2,$t2,1 #

else2:  lw $t0,1 #
    addi $t1,$a1,-1 #

else3:  lw $t1,$zero #


else4:  addi $t0,$a1,-1 #

else5:  addi $t0,$t0,2 #
    addi $t1,$t1,-1 #

end:    jr $ra

in addition this is the structure of the registers:

$a0 = base address of array (matrix), a

$a1 = n, size of matrix (number of rows and columns)

$t0 = i

$t1 = j

$t2 = k

$t3 = n*n

$t4 = arraya index - in steps

$t5 = array value

The trouble I am having is the creation of a[i,j] how is it done? here is a look at the algorithm:

 i = 0, k = 1 and j = n/2
 while (k <= n*n)
   if (i > -1 and j > -1 and j < n and i < n and a[i,j] == 0)
     a[i,j] = k
     i = i - 1, j = j +1 and k = k + 1
   else if (i < 0 and j == n) move out of upper right square
     i = 1 and j = n - 1
   else if (j == n)           move out of right side of square
     j = 0
   else if (i < 0)            move above top row
     i = n - 1
   else                       move to an already filled square
     i = i + 2 and j = j - 1
   end if - else
 end while loop

Answer 1

You can store a 2D array contiguously, with address computation: a[i, j] stored at base address + i + j * n.

For the sake of optimization, row/column traversals are made with +/-1 or +/-n increments.

Alternatively, you can allocate different areas for the rows and provide a table of row starts.