APPROACH TO POLYCELL PLACEMENT FOR LSI.

A placement technique is presented that is devoted to polycell layout of LSI and involves two steps: partitioning a circuit into blocks and placing the cells in them. The main algorithms used are: approximation method for assignment problem, Kernighan-Lin's method and branch-bound method. Improvements for these algorithms are proposed: 1. For solving assignment three selective functions are defined and among which F//2 is with prediction; 2. The objective functions and the interchange form of the Kernighan-Lin's method are tailored to meet the special requirements of geometric parameters in partitioning. In addition, the branch-bound method is used in iterative process, these making it possible to reduce the search time in many situations. The schematic diagram is given. The program is written in Fortran-4 language and has been implemented on PDP-11/34 computer.