what is the primary problem in sparse inverse covariance matrix estimation? what is the primal problem in sparse covariance matrix estimation? what is the dual problem in sparse inverse covariance how is the dual problem formed what is the dual problem formulation in sparse inverse covariance matrix what is the primary problem for sparse inverse covariance? why is the primal problem a dual problem? inverse matrix of gaussian what's the dual problem what problem is the primal problem what is the primal problem with sparse inverse covariance matrix what does dual mean for inverse matrix why is the primal problem formed what is the primal problem how is dual problem formulation inverse coefficient definition inverse matrix of gaussian what is the dual problem formulation? which problem is dual problem which problem is double problem in sparse covariance matrix estimation