Fix NCCL Error 7 by removing eager_connect_single_device#320
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Fix NCCL Error 7 by removing eager_connect_single_device#320
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The QuantizedAllReduceTest and QuantizedReduceScatterTest tests were failing with "NCCL Error 7: NCCL operation in progress" because non-blocking NCCL work.wait() returns before NCCL is ready for the next operation. Adding cuda.synchronize() between iterations ensures operations are fully complete.
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In non-blocking NCCL mode (blocking=False), eager_connect_single_device starts an async communicator init that cannot be waited on through Python APIs. When the first collective is subsequently called, NCCL returns "Error 7: operation in progress" because the init hasn't completed. Remove the eager_connect call and let the communicator be lazily initialized by the first collective, which properly handles the async init inside its ncclGroupStart/ncclGroupEnd context. Also reverts the cuda.synchronize() workaround in collectives_test.py which was insufficient.
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Summary
eager_connect_single_devicefromProcessGroupNCCL._create_pgto fix "NCCL Error 7: operation in progress" failuresblocking=False),eager_connect_single_devicestarts an async communicator init that cannot be waited on through Python APIs. The first collective then fails because the init hasn't completed.ncclGroupStart/ncclGroupEndcontext.Test plan
QuantizedAllReduceTest) should pass, which have been failing since ~Dec 2025 due to a PyTorch nightly regression in non-blocking NCCL + eager_connect interaction