Congestion Aware Placement

[behzadmehmood-rs]

Embedding code for congestion aware placement for VPR.

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Types of changes

• Bug fix (change which fixes an issue)
• New feature (change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

[soheilshahrouz]

A similar PR (#2384) was submitted a year ago. If this PR supersedes #2384, please close the old one.

[behzadmehmood-rs]

A similar PR (#2384) was submitted a year ago. If this PR supersedes #2384, please close the old one.

Yes, it supersedes PR (#2384).

[vaughnbetz]

I suggest looking at the comments in the earlier PR and addressing them -- #2384
Some of those comments are pretty important; for example there are hard-coded limits on data structures that would lead to crashes on grids of size > 400 x 400, and I think those issues are still in this PR.

[vaughnbetz]

Needs comments on what these are, what the overall congestion modeling approach is.
The approach seems to be very similar to a placement cost function that I wrote in my PhD and called NON_LINEAR_CONGESTION. At the time I measured that code it had little gain in routability for architectures with all channels the same width (in various chip regions) and the CPU time was high. Not sure if the trade-off is different with this code, but adding QoR data on some larger circuits would be important to check.

[vaughnbetz]

Also, hard-coding 400 is not good.

[behzadmehmood-rs]

I suggest looking at the comments in the earlier PR and addressing them -- #2384 Some of those comments are pretty important; for example there are hard-coded limits on data structures that would lead to crashes on grids of size > 400 x 400, and I think those issues are still in this PR.

I will address those.