“The Matrix Resurrections,” a Warner Bros. release, is rated PG-13 by the Motion Picture Association of America for violence and some language. Running time: 148 minutes.

Today's languages were each designed with different goals in mind. Matlab was built for matrix calculations, and it's great at linear algebra. The R language is meant for statistics.

We analyze two popular semidefinite programming relaxations for quadratically constrained quadratic programs with matrix variables. These relaxations are based on vector lifting and on matrix lifting; ...