Chapter 9: Tools
9-13: Placement

Electric has a number of placement tools that can rearrange a circuit so that routing is easier. The tools can handle schematic or layout cells.

To run placement, use the Floorplan and Place Current Cell command (in menu Tools / Placement). This selects an appropriate placement algorithm to run.

For more precise control over placement, you can select a particular algorithm in the Placement Preferences (in menu File / Preferences..., "Tools" section, "Placement" tab) and then use the Place Current Cell with Preferred Algorithm command. The Placement Preferences not only lets you select the algorithm, but also lets you set parameters for controlling its operation.

Figure 9.26

The bottom of the Placement Preferences dialog has controls for all placement operations. These controls set a padding percentage around each placed cell (the default is 0: make the cells touch). You can also ask the placement system to run the Sea of Gates router after placement is done (see Section 9-6-6).

These are the possible placement algorithms:

#1Gives good results quickly (seconds). Additional time and threads does not improve results
#2Recommended for highly-symmetric cell layouts (pads, memory), but may be unstable
row/colUseful for fixed-pitch cells
Genetic#1 / #2Needs long runtime. Additional threads do not help
#1Not recommended for use
#2Has best overall results. Useful for non-fixed pitch cells.
row/colUseful for fixed-pitch cells
Bottom-up partitionUsed to break large circuits into subproblems
Bottom-up placementFast and good quality for placing random-sized nodes
Min-cutSimple placer that does not use multiple threads
Simple and RandomPlaces linearly/randomly: not recommended

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