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# 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
This command performs macro placement.
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.
```tcl
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` | 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`. |
## Useful Developer Commands
If you are a developer, you might find these useful. More details can be found in the [source file](./src/MacroPlacer.cpp) or the [swig file](./src/MacroPlacer.i).
| 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](../../README.md#regression-tests).
Simply run the following script:
```shell
./test/regression
```
## Limitations
## FAQs
Check out [GitHub discussion](https://github.com/The-OpenROAD-Project/OpenROAD/discussions/categories/q-a?discussions_q=category%3AQ%26A+mpl) about this tool.
## License
BSD 3-Clause License. See [LICENSE](../../LICENSE) file.
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