@@ -22,7 +22,8 @@ Our force-directed placer takes a clustered netlist as input and generates the l
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@@ -22,7 +22,8 @@ Our force-directed placer takes a clustered netlist as input and generates the l
In the force-directed placement, there are two types of forces between nodes: attractive force and repulsive force.
In the force-directed placement, there are two types of forces between nodes: attractive force and repulsive force.
* The attractive force is ONLY applied to the nodes connected by nets. For the two-pin net connecting pin $P1$ of macro $M1$ and $P2$ of macro $M2$, the attractive force applied to $M1$ and $M2$ is calculated as $f_x = k_a * abs(P1.x - P2.x)$ and $f_y = k_a * abs(P1.y - P2.y)$, where $k_a$ is the attractive factor. If one of pins is an IO port, $k_a$ is the attractive factor times io factor. The attractive force is along the straight line joining $P1$ and $P2$. All the multi-pin nets are decomposied into two-pin nets using the start model. \[[code](https://github.com/TILOS-AI-Institute/MacroPlacement/blob/5addfc904527d764ee67429811c868c5eeb605d4/CodeElements/FDPlacement/FD.py#L1105)\]
* The attractive force is ONLY applied to the nodes connected by nets. For the two-pin net connecting pin $P1$ of macro $M1$ and $P2$ of macro $M2$, the attractive force applied to $M1$ and $M2$ is calculated as $f_x = k_a * abs(P1.x - P2.x)$ and $f_y = k_a * abs(P1.y - P2.y)$, where $k_a$ is the attractive factor. If one of pins is an IO port, $k_a$ is the attractive factor times io factor. The attractive force is along the straight line joining $P1$ and $P2$. All the multi-pin nets are decomposied into two-pin nets using the start model. \[[code](https://github.com/TILOS-AI-Institute/MacroPlacement/blob/5addfc904527d764ee67429811c868c5eeb605d4/CodeElements/FDPlacement/FD.py#L1105)\]
* The repulsive force is ONLY applied to the nodes overlapped with each other. If two macros are not overlapped, there is no repulsive force between them. For the two macros $M1$ and $M2$ overlapped with each other, the repulsive force applied to $M1$ and $M2$ is calculated as $f_x = F * abs(M1.x - M2.x) / distance(M1, M2)$ and $f_y = F * abs(M1.y - M2.y) / distance(M1, M2)$, where $F$ is the maximum move distance specified by the users. The repulsive force is along the straight line joining $M1$ and $M2$. For the cases where multiple macros are overlapped together, we calculate the repulsive forces between each pair of macros in sequence. \[[code](https://github.com/TILOS-AI-Institute/MacroPlacement/blob/5addfc904527d764ee67429811c868c5eeb605d4/CodeElements/FDPlacement/FD.py#L1082)\]
* The repulsive force is ONLY applied to the nodes overlapped with each other. If two macros are not overlapped, there is no repulsive force between them. For the two macros $M1$ and $M2$ overlapped with each other, the repulsive force applied to $M1$ and $M2$ is calculated as $f_x = F * abs(M1.x - M2.x) / distance(M1, M2)$ and $f_y = F * abs(M1.y - M2.y) / distance(M1, M2)$, where $F$ is the maximum move distance specified by the users.
If $distance(M1, M2) = 0.0$, then $f_x = F$ and $f_y = F$. The repulsive force is along the straight line joining $M1$ and $M2$. For the cases where multiple macros are overlapped together, we calculate the repulsive forces between each pair of macros in sequence. \[[code](https://github.com/TILOS-AI-Institute/MacroPlacement/blob/5addfc904527d764ee67429811c868c5eeb605d4/CodeElements/FDPlacement/FD.py#L1082)\]
After calculating all the attractive forces and repulsive forces, all the forces are normalized as following:
After calculating all the attractive forces and repulsive forces, all the forces are normalized as following:
