FastRoute¶
FastRoute is an open-source global router originally derived from Iowa State University’s FastRoute4.1.
Commands¶
global_route [-guide_file out_file]
[-verbose verbose]
[-congestion_iterations iterations]
[-grid_origin {x y}]
[-allow_congestion]
Options description:
guide_file: Set the output guides file name (e.g., -guide_fileroute.guide)verbose: Set verbosity of reporting: 0 for less verbosity, 1 for medium verbosity, 2 for full verbosity (e.g., -verbose1)congestion_iterations: Set the number of iterations made to remove the overflow of the routing (e.g.,-congestion_iterations 50)grid_origin: Set the (x, y) origin of the routing grid in DBU. For example,-grid_origin {1 1}corresponds to the die (0, 0) + 1 DBU in each x-, y- direction.allow_congestion: Allow global routing results to be generated with remaining congestion
set_routing_layers [-signal min-max]
[-clock min-max]
The set_routing_layers command sets the minimum and maximum routing
layers for signal nets, with the -signal option, and the minimum and
maximum routing layers for clock nets, with the -clock option.
Example: set_routing_layers -signal Metal2-Metal10 -clock Metal6-Metal9
set_macro_extension extension
The set_macro_extension command sets the number of GCells added to the
blockages boundaries from macros. A GCell is typically defined in terms of
Mx routing tracks. The default GCell size is 15 M3 pitches.
Example: set_macro_extension 2
set_global_routing_layer_adjustment layer adjustment
The set_global_routing_layer_adjustment command sets routing resource
adjustments in the routing layers of the design. Such adjustments reduce the number of
routing tracks that the global router assumes to exist. This promotes the spreading of routing
and reduces peak congestion, to reduce challenges for detailed routing.
You can set adjustment for a
specific layer, e.g., set_global_routing_layer_adjustment Metal4 0.5 reduces
the routing resources of routing layer Metal4 by 50%. You can also set adjustment
for all layers at once using *, e.g., set_global_routing_layer_adjustment * 0.3 reduces the routing resources of all routing layers by 30%. And, you can
also set resource adjustment for a layer range, e.g.: set_global_routing_layer_adjustment Metal4-Metal8 0.3 reduces the routing resources of routing layers Metal4,
Metal5, Metal6, Metal7 and Metal8 by 30%.
set_routing_alpha [-net net_name] alpha
By default the global router uses heuristic rectilinear Steiner minimum
trees (RSMTs) as an initial basis to construct route guides. An RSMT
tries to minimize the total wirelength needed to connect a given set
of pins. The Prim-Dijkstra heuristic is an alternative net topology
algorithm that supports a trade-off between total wirelength and maximum
path depth from the net driver to its loads. The set_routing_alpha
command enables the Prim/Dijkstra algorithm and sets the alpha parameter
used to trade-off wirelength and path depth. Alpha is between 0.0
and 1.0. When alpha is 0.0 the net topology minimizes total wirelength
(i.e. capacitance). When alpha is 1.0 it minimizes longest path between
the driver and loads (i.e., maximum resistance). Typical values are
0.4-0.8. For more information about PDRev, check the paper
[here](in https://vlsicad.ucsd.edu/Publications/Journals/j18.pdf).
You can call it multiple times for different nets.
Example: set_routing_alpha -net clk 0.3 sets the alpha value of 0.3 for net clk.
set_global_routing_region_adjustment {lower_left_x lower_left_y upper_right_x upper_right_y}
-layer layer -adjustment adjustment
The set_global_routing_region_adjustment command sets routing resource
adjustments in a specific region of the design. The region is defined as
a rectangle in a routing layer.
Example: set_global_routing_region_adjustment {1.5 2 20 30.5} -layer Metal4 -adjustment 0.7
set_global_routing_random [-seed seed]
[-capacities_perturbation_percentage percent]
[-perturbation_amount value]
The set_global_routing_random command enables randomization of global routing
results. The randomized global routing shuffles the order of the nets and randomly
subtracts or adds to the capacities of a random set of edges. The -seed
option sets the random seed and is required to enable the randomization mode. The
-capacities_perturbation_percentage option sets the percentage of edges
whose capacities are perturbed. By default, the edge capacities are perturbed by
adding or subtracting 1 (track) from the original capacity. The -perturbation_amount
option sets the perturbation value of the edge capacities. This option
will only have meaning and effect when -capacities_perturbation_percentage is used.
The random seed must be different from 0 to enable randomization of the global routing.
Example: set_global_routing_random -seed 42 -capacities_perturbation_percentage 50 -perturbation_amount 2
repair_antennas diodeCellName/diodePinName [-iterations iterations]
The repair_antenna command evaluates the global routing results to find
antenna violations, and repairs the violations by inserting diodes. The
input for this command is the diode cell and its pin names, and a prescribed
number of
iterations. By default, the command runs only one iteration to repair
antennas. It uses the antennachecker tool to identify any nets with antenna
violations and, for each such net, the exact number of diodes necessary to fix the
antenna violation.
Example: repair_antenna sky130_fd_sc_hs__diode_2/DIODE
write_guides file_name
The write_guides generates the guide file from the routing results.
Example: write_guides route.guide.
To estimate RC parasitics based on global route results, use the -global_routing
option of the estimate_parasitics command.
estimate_parasitics -global_routing
Example scripts¶
Regression tests¶
Limitations¶
FAQs¶
Check out GitHub discussion about this tool.
External references¶
The algorithm base is from FastRoute4.1, and the database comes from OpenDB
FastRoute 4.1 documentation. The FastRoute4.1 version was received from mailto:yuexu@iastate.edu on June 15, 2019, with the BSD-3 open source license as given in the FastRoute website.
Min Pan, Yue Xu, Yanheng Zhang and Chris Chu. “FastRoute: An Efficient and High-Quality Global Router. VLSI Design, Article ID 608362, 2012.” Available here.
P-D paper is C. J. Alpert, T. C. Hu, J. H. Huang, A. B. Kahng and D. Karger, “Prim-Dijkstra Tradeoffs for Improved Performance-Driven Global Routing”, IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems 14(7) (1995), pp. 890-896. Available here.
License¶
BSD 3-Clause License. See LICENSE file.