Macro Placement#

The macro placement module in OpenROAD (mpl) is based on TritonMacroPlacer, an open-source ParquetFP-based macro cell placer. The macro placer places macros/blocks honoring halos, channels and cell row “snapping”. Run global_placement before macro placement.

Approximately \(\Bigl\lceil [{\frac{numMacros}{3}}]^{1.5} \Bigr\rceil\) quadrisections of the initial placed mixed-size layout are explored and packed using ParquetFP-based annealing. The best resulting floorplan according to a heuristic evaluation function is kept.

Commands#

Note

  • Parameters in square brackets [-param param] are optional.

  • Parameters without square brackets -param2 param2 are required.

Macro Placement#

macro_placement 
    [-halo {halo_x halo_y}]
    [-channel {channel_x channel_y}]
    [-fence_region {lx ly ux uy}]
    [-snap_layer snap_layer_number]
    [-style corner_wax_wl|corner_min_wl]

Options#

Switch Name

Description

-halo

Horizontal and vertical halo around macros (microns).

-channel

Horizontal and vertical channel width between macros (microns).

-fence_region

Restrict macro placements to a region (microns). Defaults to the core area.

-snap_layer_number

Snap macro origins to this routing layer track.

-style

Placement style, to choose either corner_max_wl or corner_min_wl. The default value is corner_max_wl.

For placement style, corner_max_wl means that choosing the partitions that maximise the wirelength of connections between the macros to force them to the corners. Vice versa for corner_min_wl.

Macros will be placed with \(max(halo * 2, channel)\) spacing between macros, and between macros and the fence/die boundary. If no solutions are found, try reducing the channel/halo.

Useful developer functions#

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

macro_placement_debug

Macro placement debugging. Note that GUI must be present for this command, otherwise a segfault will occur.

Example scripts#

Example scripts demonstrating how to run TritonMacroPlace on a sample design of east_west as follows:

./test/east_west.tcl
./test/east_west1.tcl
./test/east_west2.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.

License#

BSD 3-Clause License. See LICENSE file.