[nileshnegi]

Motivation

The Rome model-matching logic in rome_models.cc contains hardcoded topology patterns for specific AMD GPUs (MI2XX and MI3XX series). These patterns define optimized ring/tree topologies based on known GPU-to-GPU connectivity matrices.

gfx1250 has a different interconnect topology that doesn't match any existing Rome model. When the matcher attempts to find a matching model and fails, it falls back to generic search anyway, but only after wasting cycles on futile pattern comparisons. More critically, a partial or incorrect match could select a suboptimal topology.

This change proactively skips Rome model matching for gfx1250, ensuring the generic topology search algorithm is used from the start.

Technical Details

• Modified the skipPresetTopoMatching assignment in initTransportsRank() to include an architecture check
• When comm->topo->nodes[GPU].nodes[0].gpu.gcn matches "gfx1250", preset matching is skipped. Rome model parsers (parseChordalRing, parseA2a8P, parseRome4P2H, parse1H16P, parse4H4P, parseGIOTopos) are bypassed.
• Control falls through to the generic ncclTopoSearchRec() algorithm

Issue Tracking

JIRA ID: AICOMRCCL-1932

Test Plan

Added TEST(SkipPresetTopoMatching, Gfx1250_SkipsRomeModelMatching) to test/RcclWrapTests.cpp

Test Result

Submission Checklist

• Look over the contributing guidelines at https://github.com/ROCm/rocm-systems/blob/develop/CONTRIBUTING.md.

[therock-pr-bot]

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🧪 Unit Test	⚠️ Warning	Error: Source/code files changed without an accompanying unit test. Expected: add at least one test file named like test_<name>.py / test_<name>.cpp (or <name>_test.*). Current: code file(s) changed: projects/rccl/src/init.cc, projects/rccl/test/RcclWrapTests.cpp; no test file found
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[Copilot]

Pull request overview

This PR updates RCCL’s topology initialization to bypass Rome preset topology model matching on gfx1250 so the generic topology search is used immediately, and adds a unit test intended to validate the new behavior on real gfx1250 hardware.

Changes:

• Update initTransportsRank() to set comm->topo->skipPresetTopoMatching when the detected GPU arch matches gfx1250.
• Add a new isolated gtest that initializes a communicator and checks skipPresetTopoMatching / romeTopoModelIdx on gfx1250.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
projects/rccl/src/init.cc	Extends skipPresetTopoMatching logic to force skipping Rome preset matching on gfx1250.
projects/rccl/test/RcclWrapTests.cpp	Adds a new isolated runtime test for gfx1250 preset-matching skip behavior.

Suppressed comments (1)

projects/rccl/test/RcclWrapTests.cpp:2420

• After skipping on non-gfx1250, the remaining assertions can be unconditional. Also, destroy should not use NCCLCHECK here for the same reason; prefer ASSERT_EQ to ensure failures are surfaced and the test doesn't continue with invalid state.

        // Cast to internal struct to access topo
        ncclComm* comm = commHandle;

        if (isGfx1250) {
            // gfx1250 should skip preset topo matching

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