Form reduced matrix A that contains only rows that are active at the
solution.
Ared = vstack[Alow, Aupp]
Active constraints are guessed from the primal and dual solution returned by
the ADMM.
@param work Workspace
@return Number of rows in Ared, negative if error
Form reduced matrix A that contains only rows that are active at the solution. Ared = vstack[Alow, Aupp] Active constraints are guessed from the primal and dual solution returned by the ADMM. @param work Workspace @return Number of rows in Ared, negative if error