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Detailed Routing

The Detailed Routing (drt) module in OpenROAD is based on the open-source detailed router, TritonRoute. TritonRoute consists of several main building blocks, including pin access analysis, track assignment, initial detailed routing, search and repair, and a DRC engine. The initial development of the router is inspired by the ISPD-2018 initial detailed routing contest. However, the current framework differs and is built from scratch, aiming for an industrial-oriented scalable and flexible flow.

TritonRoute provides industry-standard LEF/DEF interface with support of ISPD-2018 and ISPD-2019 contest-compatible route guide format.

Commands

- Parameters in square brackets `[-param param]` are optional.
- Parameters without square brackets `-param2 param2` are required.

Detailed Route

This command performs detailed routing.

Developer arguments

-or_seed, -or_k

Distributed arguments

-distributed , -remote_host, -remote_port, -shared_volume, -cloud_size

detailed_route 
    [-output_maze filename]
    [-output_drc filename]
    [-output_cmap filename]
    [-output_guide_coverage filename]
    [-drc_report_iter_step step]
    [-db_process_node name]
    [-disable_via_gen]
    [-droute_end_iter iter]
    [-via_in_pin_bottom_layer layer]
    [-via_in_pin_top_layer layer]
    [-or_seed seed]
    [-or_k k]
    [-bottom_routing_layer layer]
    [-top_routing_layer layer]
    [-verbose level]
    [-distributed]
    [-remote_host rhost]
    [-remote_port rport]
    [-shared_volume vol]
    [-cloud_size sz]
    [-clean_patches]
    [-no_pin_access]
    [-min_access_points count]
    [-save_guide_updates]
    [-repair_pdn_vias layer]
    [-single_step_dr]

Options

Switch Name	Description
`-output_maze`	Path to output maze log file (e.g. `output_maze.log`).
`-output_drc`	Path to output DRC report file (e.g. `output_drc.rpt`).
`-output_cmap`	Path to output congestion map file (e.g. `output.cmap`).
`-output_guide_coverage`	Path to output guide coverage file (e.g. `sample_coverage.csv`).
`-drc_report_iter_step`	Report DRC on each iteration which is a multiple of this step. The default value is `0`, and the allowed values are integers `[0, MAX_INT]`.
`-db_process_node`	Specify the process node.
`-disable_via_gen`	Option to diable via generation with bottom and top routing layer. The default value is disabled.
`-droute_end_iter`	Number of detailed routing iterations. The default value is `-1`, and the allowed values are integers `[1, 64]`.
`-via_in_pin_bottom_layer`	Via-in pin bottom layer name.
`-via_in_pin_top_layer`	Via-in pin top layer name.
`-or_seed`	Refer to developer arguments here.
`-or_k`	Refer to developer arguments here.
`-bottom_routing_layer`	Bottommost routing layer name.
`-top_routing_layer`	Topmost routing layer name.
`-verbose`	Sets verbose mode if the value is greater than 1, else non-verbose mode (must be integer, or error will be triggered.)
`-distributed`	Refer to distributed arguments here.
`-clean_patches`	Clean unneeded patches during detailed routing.
`-no_pin_access`	Disables pin access for routing.
`-min_access_points`	Minimum access points for standard cell and macro cell pins.
`-save_guide_updates`	Flag to save guides updates.
`-repair_pdn_vias`	This option is used for PDKs where M1 and M2 power rails run in parallel.

Developer arguments

Some arguments that are helpful for developers are listed here.

Switch Name	Description
`-or_seed`	Random seed for the order of nets to reroute. The default value is `-1`, and the allowed values are integers `[0, MAX_INT]`.
`-or_k`	Number of swaps is given by $k * sizeof(rerouteNets)$. The default value is `0`, and the allowed values are integers `[0, MAX_INT]`.

Detailed Route Debugging

The following command and arguments are useful when debugging error messages from drt and to understand its behavior.

detailed_route_debug 
    [-pa]
    [-ta]
    [-dr]
    [-maze]
    [-net name]
    [-pin name]
    [-box x1 y1 x2 y2]
    [-iter iter]
    [-pa_markers]
    [-dump_dr]
    [-dump_dir dir]
    [-dump_last_worker]
    [-pa_edge]
    [-pa_commit]
    [-write_net_tracks]

Options

Switch Name	Description
`-pa`	Enable debug for pin access.
`-ta`	Enable debug for track assignment.
`-dr`	Enable debug for detailed routing.
`-maze`	Enable debug for maze routing.
`-net`	Enable debug for net name.
`-pin`	Enable debug for pin name.
`-box`	Set the box for debugging given by lower left/upper right coordinates.
`-worker`	Debugs routes that pass through the point `{x, y}`.
`-iter`	Specifies the number of debug iterations. The default value is `0`, and the accepted values are integers `[0, MAX_INT`.
`-pa_markers`	Enable pin access markers.
`-dump_dr`	Filename for detailed routing dump.
`-dump_dir`	Directory for detailed routing dump.
`-pa_edge`	Enable visibility of pin access edges.
`-pa_commit`	Enable visibility of pin access commits.
`-write_net_tracks`	Enable writing of net track assigments.

Check Pin Access

This function checks pin access.

pin_access
    [-db_process_node name]
    [-bottom_routing_layer layer]
    [-top_routing_layer layer]
    [-min_access_points count]
    [-verbose level]
    [-distributed]
    [-remote_host rhost]
    [-remote_port rport]
    [-shared_volume vol]
    [-cloud_size sz]

Options

Switch Name	Description
`-db_process_node`	Specify process node.
`-bottom_routing_layer`	Bottommost routing layer.
`-top_routing_layer`	Topmost routing layer.
`-min_access_points`	Minimum number of access points per pin.
`-verbose`	Sets verbose mode if the value is greater than 1, else non-verbose mode (must be integer, or error will be triggered.)
`-distributed`	Refer to distributed arguments here.

Distributed Arguments

We have compiled all distributed arguments in this section.

Additional setup is required. Please refer to this [guide](./doc/Distributed.md).

Switch Name	Description
`-distributed`	Enable distributed mode with Kubernetes and Google Cloud.
`-remote_host`	The host IP.
`-remote_port`	The value of the port to access from.
`-shared_volume`	The mount path of the nfs shared folder.
`-cloud_size`	The number of workers.

Useful Developer Commands

If you are a developer, you might find these useful. More details can be found in the source file or the swig file.

Command Name	Description
`detailed_route_set_default_via`	Set default via.
`detailed_route_set_unidirectional_layer`	Set unidirectional layer.
`step_dr`	Refer to function `detailed_route_step_drt`.
`check_drc`	Refer to function `check_drc_cmd`.

Example scripts

Example script demonstrating how to run TritonRoute on a sample design of gcd in the Nangate45 technology node.

# single machine example 
./test/gcd_nangate45.tcl

# distributed example
./test/gcd_nangate45_distributed.tcl

Regression tests

There are a set of regression tests in ./test. For more information, refer to this section.

Simply run the following script:

./test/regression

Limitations

FAQs

Check out GitHub discussion about this tool.

References

Please cite the following paper(s) for publication:

A. B. Kahng, L. Wang and B. Xu, "TritonRoute: The Open Source Detailed Router", IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems (2020), doi:10.1109/TCAD.2020.3003234. (.pdf)
A. B. Kahng, L. Wang and B. Xu, "The Tao of PAO: Anatomy of a Pin Access Oracle for Detailed Routing", Proc. ACM/IEEE Design Automation Conf., 2020, pp. 1-6. (.pdf)

Authors

TritonRoute was developed by graduate students Lutong Wang and Bangqi Xu from UC San Diego, and serves as the detailed router in the OpenROAD project.

License

BSD 3-Clause License. See LICENSE file.