Large Scale Placement with Explicit Cell Movement Control

Nowadays a circuit placement algorithm often faces a problem size of multi-million objects, with excessive fixed blockages. We present a new efficient quadratic placement algorithm that scales well to the large-scale circuit placement problems. Instead of adding spreading forces into the quadratic system to push cells away from congestions, we simulate the cell diffusion process and use dummy anchor cellsto guide the real cell movements. By using the concept of anchor cells, our placer has explicit control on how and where to move cells. Meanwhile, the usage of anchor cells significantly reduces the complexity of the Hessian of the quadratic system, which encapsulates the netlist conductivity. The Hessian matrix in our quadratic placer is extremely sparse, with 2-3 nonzero entries in most of rows/colums. Such a matrix is trivial to solve. From our experiments on the large-scale ISPD 2005 placement benchmarks, our placer achieved a 23x speedup on the CPU usage of the quadratic solver, and comparable wirelengths to existing state-of-art placers.