accessing elements in sparse matrix

Dear all

I have 2 very big and very sparse matrix A and B. A and B are correlated, which means that if A(i,j) ~= 0 then B(i,j)~=0 and vice versa. In my program, after accessed A(i,j), then B(i,j) will be accessed. The reason is that 2 sparse matrix is smaller than 1 3D matrix which can't be sparse.

In my impression (only guess) that sparse matrix is essentially a linked list. In order to find A(i,j), we need to traverse all nonzero elements to find the right one. In my case, there are 2 traverse along A and B.

My question is that is it possible to find the real index of A(i,j), and then another traverse in B could be saved.

Thanks a lot in advance.