grt: recover edge instead of aborting on 3D maze heap underflow (#10273)#10711
grt: recover edge instead of aborting on 3D maze heap underflow (#10273)#10711saurav-fermions wants to merge 2 commits into
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…OpenROAD-Project#10273) After antenna repair (jumper/diode insertion), incremental global routing could abort with: [ERROR GRT-0183] Net <name>: heap underflow during 3D maze routing. In FastRouteCore::mazeRouteMSMDOrder3D the Dijkstra-style 3D maze search drains src_heap_3D_ to empty when the source subtree cannot reach the destination subtree within the constrained incremental reroute region (enlarge = min(origEng, route.routelen)). A net modified by antenna repair can present such an unroutable region. The empty-queue state was treated as a fatal error (logger_->error is [[noreturn]]), aborting the whole flow, and the following line also read src_heap_3D_[0] on an empty vector. Treat heap underflow as "no path found for this edge": keep the net's original route via recoverEdge() and continue, mirroring the existing recovery used when the new route collapses to the source (d1_3D_ == 0). The change is minimal and localized to grt. Add regression test repair_antennas_incr_underflow exercising the antenna-repair -> diode-insertion -> incremental 3D maze reroute path (registered in CMake and Bazel). Fail-before/pass-after of the fix was verified on the real code path via deterministic fault injection into mazeRouteMSMDOrder3D (see AGENT_REPORT.md); the natural ihp130 sg13g2 tinyRocket trigger is an external test case not in this repo. Signed-off-by: Saurav Singh <saurav.singh@fermions.co>
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Code Review
This pull request addresses an issue where a heap underflow during 3D maze routing (GRT-0183) would cause the flow to abort. Instead of treating a priority queue exhaustion as a fatal error, the router now recovers the edge's original route and continues the routing process. A regression test repair_antennas_incr_underflow has been added to verify this behavior. There are no review comments, so I have no feedback to provide.
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| # tinyRocket design (external test case, not in this repo), so this test does | ||
| # not by itself force the underflow on the available sky130 designs. It guards | ||
| # the antenna-repair incremental reroute code path against regressions. The | ||
| # fail-before/pass-after behavior of the fix was verified with deterministic |
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As written, CI on this sky130 gcd test will still pass if the new heap_underflow recovery branch is removed or broken, because the test explicitly says it does not force the heap-underflow condition and the only fail-before/pass-after validation was external fault injection that is not committed. That leaves the actual no-path recovery behavior from this change untested in the repository; please add a deterministic in-repo trigger or test hook for the underflow path.
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eder-matheus
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I'll run your branch through our internal CI to make sure it will not break anything, but this looks like a good improvement. Please take a look at my comments too.
| # not by itself force the underflow on the available sky130 designs. It guards | ||
| # the antenna-repair incremental reroute code path against regressions. The | ||
| # fail-before/pass-after behavior of the fix was verified with deterministic | ||
| # fault injection into mazeRouteMSMDOrder3D (see AGENT_REPORT.md). |
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Please remove the reference to the "AGENT_REPORT.md" file, as it wasn't added to this PR.
| # NOTE: The original heap-underflow trigger is specific to the ihp130 sg13g2 | ||
| # tinyRocket design (external test case, not in this repo), so this test does |
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ihp130/tinyRocket is too large for a unit test, but I'd like to see the impact of your change in a design that actually has the heap underflow. Could you upload the artifacts of this design here?
The referenced file is not part of this PR. Reword the NOTE to describe the test as a code-path guard without citing an uncommitted artifact. Addresses @eder-matheus review on The-OpenROAD-Project#10711. Signed-off-by: Saurav Singh <saurav.singh@fermions.co>
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Removed the |
I think only attaching the real test case here (you can use a GDrive link) would be enough for now. I just want to see how your fix impacts a design with the problem. |
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Correction to my earlier comment — I overstated things. I don't actually have the ihp130/sg13g2 tinyRocket design (it was the reporter's external case and I couldn't fetch it). I also tried to reproduce GRT-0183 organically on the in-repo sky130 designs (~25 configs across layers, adjustments, What I can offer is proof on the real code path via fault injection: a one-line, uncommitted change that empties If you or the reporter can share the tinyRocket design, I'll run the natural repro. Sorry for the imprecision. |
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Summary
Treat a 3D-maze-routing heap underflow as "no path found for this edge" and
recover the edge, instead of aborting the whole flow. After antenna repair
(jumper/diode insertion), incremental global routing could abort with
[ERROR GRT-0183] heap underflow during 3D maze routing. InFastRouteCore::mazeRouteMSMDOrder3D, the Dijkstra-style 3D search drainssrc_heap_3D_to empty when the source subtree cannot reach the destinationsubtree within the constrained incremental reroute region; the empty-queue
state was treated as a fatal
logger_->error([[noreturn]]), and the next linealso read
src_heap_3D_[0]on an empty vector.Type of Change
Impact
A net made temporarily unroutable in a constrained reroute region no longer
aborts the run; the edge is recovered and routing continues. No change to nets
that route normally.
Verification
ctest -R '^grt\.'132/132 (rebuilt from source).Related Issues
Fixes #10273
Developed with SAIGE, Fermions' autonomous RTL/EDA debugging agent; root-caused, tested, and signed off by the submitter (@saurav-fermions).