Fix route priority sort indexing

[bdice]

Summary

• Fix an out-of-bounds host read in adapted_sol_t::priority_remove_diff_routes by sorting route ids directly on routes[id].length.
• The old comparator indexed a compact route_priority vector by route id, which could corrupt the host heap and intermittently abort ROUTING_TEST.

Closes #1221. Closes #866. Closes #783.

Validation

Running many times under ASan no longer triggers the SIGABRT, though it was very hard to reproduce the previous failure before this fix.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR fixes an intermittent host heap corruption crash in the routing adapter by removing unsafe vector indexing from the sort comparator. The comparator now compares route lengths directly instead of using route IDs as indices into a temporary priority vector, eliminating out-of-bounds access when route IDs exceed the vector size.

Changes

Route Priority Sort Bounds Fix

Layer / File(s)	Summary
Sort comparator route length access cpp/src/routing/adapters/adapted_sol.cuh	The sort comparator in priority_remove_diff_routes now directly accesses routes[i].length and routes[j].length instead of indexing into a pre-allocated route_priority vector, eliminating out-of-bounds reads when route IDs ≥ vector size.

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and accurately summarizes the primary change: fixing route priority sort indexing to resolve an out-of-bounds read issue.
Linked Issues check	✅ Passed	The PR fully addresses issue #1221 by changing the comparator to compare routes[i].length and routes[j].length directly instead of indexing a compact route_priority vector, eliminating out-of-bounds access.
Out of Scope Changes check	✅ Passed	All changes are scoped to fixing the comparator in adapted_sol.cuh as required; no unrelated modifications are present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description check	✅ Passed	The description directly addresses the changeset by explaining the bug fix for out-of-bounds host read in adapted_sol_t::priority_remove_diff_routes and the specific implementation change.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[hlinsen]

Great catch, thank you @bdice

[mlubin]

Uh oh, I see a crash in routing test:
https://github.com/NVIDIA/cuopt/actions/runs/25878108924/job/76057979097?pr=1222#step:12:17602

[ RUN      ] level0_retail/retail_float_test_t.CVRPTW_Retail/18
ROUTING_TEST: /tmp/conda-bld-output/bld/rattler-build_libmps-parser/work/cpp/src/routing/local_search/local_search.cu:315: void cuopt::routing::detail::local_search_t<i_t, f_t, REQUEST>::run_best_local_search(cuopt::routing::detail::solution_t<i_t, f_t, REQUEST>&, bool, bool, bool) [with i_t = int; f_t = float; cuopt::routing::request_t REQUEST = cuopt::routing::request_t::VRP]: Assertion `(cost_after - cost_before) - move_candidates.cycles.total_cycle_cost < 1.&& "Cost mismatch after a move"' failed.

[rgsl888prabhu]

Think this is same failure as noted in the bug #1221

[bdice]

The double free or corruption (out) error is what this PR fixes.

There seems to be a separate bug in the same test:

Assertion `(cost_after - cost_before) - move_candidates.cycles.total_cycle_cost < 1.&& "Cost mismatch after a move"' failed.

Attempting to reproduce that now.