Editing Magic (software) (section)

=== Design rule checking ===
Magic features real-time [[design rule checking]], something that some costly commercial VLSI design software packages don't feature. Magic implements this by counting distance using [[Manhattan distance]], which is much faster to compute than [[Euclidean distance]]. Magic versions from 7.3 properly compute Euclidean distance when given the <code>drc euclidean on</code> command.  Euclidean distance checks are a trivial extension of the Manhattan distance checks, and require very little overhead.  On a straight-line edge, the Manhattan and Euclidean distances are the same.  Only on corners do the two distances diverge.  When checking corners, it is only necessary to keep track of the direction of search from the corner point.  Any geometry found inside the square representing the Manhattan distance from the corner undergoes an additional check to see if the same geometry lies outside the quarter-circle radius representing the Euclidean distance.  Since this additional check is applied only to geometry found in violation of the Manhattan distance rule, it is not invoked often, so the computational overhead is very small.

Magic currently runs under [[Linux]], although versions exist for [[DOS]], [[OS/2]], and other [[operating systems]]. Magic is frequently used in conjunction with [[IRSIM]]<ref>[http://opencircuitdesign.com/irsim/ IRSIM switch-level simulator]</ref> and other [[electronic circuit simulation|simulation programs]].