matrix multiplication using verilog

I'm a bit rusty, but won't 'ra' always be a 4x4 matrix of all ones or all zeros depending on the state of 'a' at the rising edge of clk? And likewise for 'rb'? So the output will always be a 4x4 matrix of zeros since in all cases 'sum' resolves to 0 since the matrix length is even?

((((0 xor 0*0) xor 0*0) xor 0*0) xor 0*0)=0

((((0 xor 1*0) xor 1*0) xor 1*0) xor 1*0)=0

((((0 xor 0*1) xor 0*1) xor 0*1) xor 0*1)=0

((((0 xor 1*1) xor 1*1) xor 1*1) xor 1*1)=0

Maybe try an odd matrix dimension and see if you get a different result.