Issue

This Content is from Stack Overflow. Question asked by Kilkik

We consider the following code on Matlab with N an integer.

diag = 3*speye(N,N);           % diagonal
subd=-sparse(2:N,1:N-1,1,N,N);
A=diag+subd+2*subd';
C=full(A);

If I am not wrong, sparse format keeps only non-zero entries, so it needs less memory. I noticed that when N=2,…,6, the size of A is bigger than the size of C even if A is in sparse format. Can someone explain why ?

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