BoxRouter: A New Global Router Based on Box Expansion and Progressive ILP Minsik Cho and David Z' Pa

1
BoxRouter A New Global Router Based on Box
Expansion and Progressive ILPMinsik Cho and
David Z. PanECE Dept. Univ. of Texas at
AustinDAC 2006, July 24-28
2
Introduction

• Global Routing plans approximate route of each
  net to reduce complexity of detailed router
• Goal Optimize wire density during global routing
• Improve manufacturability
• Potential to feedback interconnect information

3
Steps

• PreRouting captures congested areas
• BoxRouting starts in most congested area and
  expands box to cover entire chip
• Progressive integer linear programming (ILP)
  technique to route wires in box
• Maze routing algorithm for rest of wires
• PostRouting reroutes wires without rip-up
• Parameter controls trade-off between length and
  routability

4
BoxRouter

• Route as many wires inside box as possible with
  ILP
• Maze routing algorithm if ILP fails

5
Algorithm
6
Steps
2) Box around congested area
3) ILP routing between G-cells
1) PreRouting Identify congested area
6) Repeat
4) Maze routing
5) Expand box
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PostRouting

• Start from congested area
• Reroute wires to reduce length (if possible)
• Reroute surrounding wires
• Repeat
• Parameter controls cost function
• Wirelength vs. routability

8
Experimental Results

• Larger box expansion can improve results at a
  cost of runtime
• Compared to Labyrinth
• Reduce wirelength by 14.3
• Reduce overflow by 91.7
• Compared to Fengshui
• Reduce overflow by 79
• Compared to multicommodity flow-based router
• 15.7x faster
• 4.2 shorter wirelength