The next possibility is dividing B and C into column blocks,
and computing C block by block. Recall that we use the notation
to mean the submatrix in rows i through j and columns
k through l. We partition
where each 
is 
,
and similarly for C. Our column block algorithm is then
Assuming 
, so that fast
memory can accommodate 
, 
and one column of A
simultaneously, our memory reference count is as follows:
for reading and writing each block
of C once, 
for reading each block of B once, and 
for
reading A N times. This yields 
, so that M needs to
grow with n to keep q large.
