Proximity effect correction by dose modulation is widely practiced in electron-beam lithography. Optical proximity control is also possible using a combination of shape adjustment and phase control. Assigning "the right" dose (or fill factor and phase for optics) is a well known mathematical inverse problem. Linear programming, by definition, is the appropriate method for determining dose. In the past, the technique was too slow for full-scale implementation in mask making. Here, the authors discuss how recent developments in computer speed and architecture have improved the prospects for full-scale implementation. In addition, the authors discuss some numerical techniques, analogous to gridding and relaxation, that make linear programming more attractive in mask making. (c) 2007 American Vacuum Society.