fix(rccl): disable Rome model matching for gfx1250

projects/rccl/src/init.cc

@@ -1626,7 +1626,14 @@ static ncclResult_t initTransportsRank(struct ncclComm* comm, struct ncclComm* p
     }
   }
 
-  comm->topo->skipPresetTopoMatching = !uniformRanksPerHost(comm, nranks);
+  {
+    bool nonUniformRanks = !uniformRanksPerHost(comm, nranks);
+    bool isGfx1250 = comm->topo->nodes[GPU].count > 0 && IsArchMatch(comm->topo->nodes[GPU].nodes[0].gpu.gcn, "gfx1250");
+    comm->topo->skipPresetTopoMatching = nonUniformRanks || isGfx1250;
+    if (comm->topo->skipPresetTopoMatching) {
+      INFO(NCCL_INIT, "Rome model matching disabled %s", isGfx1250 ? "on gfx1250" : "due to non-uniform ranks per host");
+    }
+  }
 
   timers[TIMER_INIT_GRAPHS] = clockNano();
   // Get rings and trees

projects/rccl/test/RcclWrapTests.cpp

@@ -2386,4 +2386,45 @@ TEST(RcclAllReduceDdaDecision, SymEligible_YieldsToSymmetricKernel)
                                                 /*symEligible=*/true, /*ceAllReduceAllowed=*/true));
 }
 
+// ---------------------------------------------------------------------------
+// Tests for skipPresetTopoMatching: gfx1250 skips Rome model matching.
+// Runs on real GPU, initializes a communicator, and checks internal state.
+// ---------------------------------------------------------------------------
+
+TEST(SkipPresetTopoMatching, Gfx1250_SkipsRomeModelMatching)
+{
+    RUN_ISOLATED_TEST("Gfx1250_SkipsRomeModelMatching", []()
+    {
+        int numDevices = 0;
+        ASSERT_EQ(hipGetDeviceCount(&numDevices), hipSuccess);
+        if (numDevices < 1) {
+            GTEST_SKIP() << "No devices available.";
+        }
+
+        // Check if this is gfx1250
+        hipDeviceProp_t prop{};
+        ASSERT_EQ(hipGetDeviceProperties(&prop, 0), hipSuccess);
+        bool isGfx1250 = (strncmp(prop.gcnArchName, "gfx1250", 7) == 0);
+        if (!isGfx1250) {
+            GTEST_SKIP() << "Test only applicable on gfx1250 hardware.";
+        }
+
+        ncclComm_t commHandle{};
+        ncclUniqueId id{};
+        ASSERT_EQ(ncclGetUniqueId(&id), ncclSuccess);
+        ASSERT_EQ(hipSetDevice(0), hipSuccess);
+        ASSERT_EQ(ncclCommInitRank(&commHandle, 1, id, 0), ncclSuccess);
+
+        // Cast to internal struct to access topo
+        ncclComm* comm = commHandle;
+
+        // gfx1250 should skip preset topo matching
+        EXPECT_TRUE(comm->topo->skipPresetTopoMatching);
+        // Rome model index should be NONE (no preset matched)
+        EXPECT_EQ(comm->topo->romeTopoModelIdx, RCCL_ROME_TOPO_PRESET_MODEL_IDX_NONE);
+
+        ASSERT_EQ(ncclCommDestroy(commHandle), ncclSuccess);
+    });
+}
+
 } // namespace RcclUnitTesting