Jezz: An effective legalization algorithm for minimum displacement

In this paper, we present a new method for circuit legalization called Jezz, which is, on average, 42.7% better than the classic legalization algorithm Tetris in terms of overall cell displacement, and 2.4% better than Abacus, a legalization algorithm that uses a quadratic function to compute the minimum cost for moving a cell, different from Jezz, that uses a linear function. The legalization step aligns cells to sites within the circuit rows and removes any overlapping among them while trying to minimize the total displacement of cells. Jezz can perform both full and incremental legalization, indicating the impact caused by inserting a cell in a row. It intrinsically handles cell-to-site alignment and has blockage support. A cache system is used to allow fast lookup during incremental legalization, allowing Jezz to support detailed placement algorithms. Although Jezz can be 20× slower than Tetris, the full legalization of a circuit with 200k cells takes less than a second, which makes Jezz suitable even for large scale designs, as a full legalization is run just a few times during the design flow.