So as we know the approximation of the inverse of the hessian matrix using the BFGS method is calculated with the following formulas :
$$q_{k+1} = (I-p_k s_k (y_k)^T)q_k(I- p_k y_k (s_k)^T) + p_k s_k (s_k)^T$$ $$p_k = 1/y_k(y_k)^T$$ $$s_k = x_{k+1} - x_{k}$$ $$y_k = \nabla f(x_{k+1}) - \nabla f(x_k)$$ Where $x$ is the input, $k = 1,2,3 ... $ the iteration number, $I$ identity matrix and $q_0 = I$ too.
Given $x_0 = 60x80$ matrix, calculating the above given BFGS equations won't work because of the matrix multiplication (with $I,q_0 = 80x80$ matrices)
what am i doing wrong ?