Optimally bracing grid frameworks with holes

We consider the bracing problem of a square grid framework possibly with holes and present an efficient algorithm for making the framework infinitesimally rigid by augmenting it with the minimum number of diagonal braces. This number of braces matches the lower bound given by Gáspár, Radics and Recski . Our contribution extends the famous result on bracing the rectangular grid framework by Bolker and Crapo .