Incremental placement algorithm for standard-cell layout

To satisfy timing constraints or complete clock net routing, it is sometimes necessary to make local modifications to circuits after placement. Redoing the time-consuming process of placement after each of these changes is no longer affordable. In this paper, we present a new algorithm W-ECOP to effect incremental changes on a standard cell layout automatically. This algorithm deals with cell inserting and cell moving based on rows instead of on cells as most placement algorithms usually do. Our method tries to minimize the adjustment on the initial placement and optimize the wirelength. Testing of W-ECOP on a group of practical test cases shows our algorithm can successfully accomplish incremental placement, with good quality and high speed