“…This method is the latest in a series of exact algorithm proposals for variants of MIQPs with cardinality constraints, often focusing on portfolio optimization applications, that includes, in particular, [52,295,48,60,165,164,18,88,107]. A recent survey of models and exact methods for portfolio selection tasks, including cases with cardinality constraints, is provided by [250]; another fairly broad overview of MIQP with cardinality constraints can be found in [355]. A MIQP algorithm for the special case of feature selection (or sparse regression), 0 -cons( Ax − b 2 , k, R n ), was proposed in [45], including the aforementioned ways to compute tighter big-M bounds; some statistical properties of such sparse regression problems and relations to their regularized versions are discussed in, e.g., [348,298].…”