Properties of numerical algorithms related to computing controllability

Absfmct- % numerical propertics of some methods for computing conbollab~arellsedinanexpositorywaytomotmafeawtdernnder-standing of numerical oomputstions. In particular, the numerical rank of a matrix, the numerical stability of algorithms, the sensitivity of prublem, andthesdingofproblemsaredlscussed.Anmuericdiystable~ ia glven for computing cmdhbility, but it is pointed out W a meaoure of the distance of the given system from the nearest uncontrollable system would be more usefi~I, and this appears to be an open computational problem. I