How should I compute for Q and b value with sparse matrix?

[VivianZ99]

Can I directly follow the provided equation as shown in the picture? (with matrices such as A, M already converted to sparse matrix)

Or should I compute the value for each i j? If so, how should I compute those values?

[abhimadan]

Take a look at this page, which describes how Eigen's sparse matrices work.

[VivianZ99]

Dose it mean I can use the matrix products and basic operations listed in that page?

[alecjacobson]

yes, you may use matrix products etc.