Practical Problems in VLSI Physical Design L-RST Algorithm (1/16)
L-Shaped RST Routing Perform L-RST using node b as the root
First step: build a separable MST Prim with w(i,j) = (D(i,j), −|y(i) − y(j)|, − max{x(i), x(j)})
Practical Problems in VLSI Physical Design L-RST Algorithm (2/16)
First Iteration
Practical Problems in VLSI Physical Design L-RST Algorithm (3/16)
Separable MST Construction
Practical Problems in VLSI Physical Design L-RST Algorithm (4/16)
Separable MST Construction (cont)
Practical Problems in VLSI Physical Design L-RST Algorithm (5/16)
Constructing a Rooted Tree Node b is the root node
Based on the separable MST (initial wirelength = 32) Bottom-up traversal is performed on this tree during L-RST
routing
Practical Problems in VLSI Physical Design L-RST Algorithm (6/16)
Partial L-RST for Node C
Practical Problems in VLSI Physical Design L-RST Algorithm (7/16)
Partial L-RST for Node E
Practical Problems in VLSI Physical Design L-RST Algorithm (8/16)
Partial L-RST for Node G
Practical Problems in VLSI Physical Design L-RST Algorithm (9/16)
Partial L-RST for Node D
Practical Problems in VLSI Physical Design L-RST Algorithm (10/16)
Partial L-RST for Node D (cont)
Practical Problems in VLSI Physical Design L-RST Algorithm (11/16)
Partial L-RST for Node F
best case
Practical Problems in VLSI Physical Design L-RST Algorithm (12/16)
Partial L-RST for Node F (cont)
best case
Practical Problems in VLSI Physical Design L-RST Algorithm (13/16)
Processing the Root Node
best case
Practical Problems in VLSI Physical Design L-RST Algorithm (14/16)
Top-down Traversal In order to obtain the final tree
upper upper
lower lower upper
lower lower/upper upper
Practical Problems in VLSI Physical Design L-RST Algorithm (15/16)
Final Tree Wirelength reduction
Initial wirelength − total overlap = 32 − 4 = 28
Practical Problems in VLSI Physical Design L-RST Algorithm (16/16)
Stable Under Rerouting Steiner points are marked X
Wirelength does not reduce after rerouting
