Applicability

Product	Supported
Atlas 350 Accelerator Card	☓
Atlas A3 training product/Atlas A3 inference product	√
Atlas A2 training product/Atlas A2 inference product	√
Atlas 200I/500 A2 inference product	☓
Atlas inference product	☓
Atlas training product	☓

For Atlas A2 training product/Atlas A2 inference product, only the Atlas 800T A2 training server, Atlas 900 A2 PoD cluster basic unit, and Atlas 200T A2 Box16 heterogeneous subrack are supported.

Function

Starts a group call.

Multiple functions are called between HcclGroupStart and HcclGroupEnd and executed collectively as a single unit. Group call supports the following scenarios:

Single-process multi-thread NPU management: The communicator management APIs HcclCommInitClusterInfo, HcclCommInitClusterInfoConfig, HcclCommInitRootInfo, HcclCommInitRootInfoConfig and HcclCommDestroy can be called.
Grouping multiple collective communication operations
Grouping multiple point-to-point communication operations

Prototype

HcclResult HcclGroupStart()

Parameters

None.

Returns

HcclResult: HCCL_SUCCESS on success, or else failure.

Constraints

Using the group call APIs for communicator management is exclusively supported in single-node environments.
In a group call, mixing communicator management, collective communication, and point-to-point communication APIs is not allowed.
Calling the HcclBatchSendRecv API is not supported when grouping multiple point-to-point communications.
The HcclGroupStart and HcclGroupEnd APIs must be used in pairs, with HcclGroupStart preceding HcclGroupEnd.

Call Example

Example 1: Single-process multi-thread NPU management

HcclComm hccl_comms[devCount];
HcclGroupStart();
for(int i = 0; i < ndev; i++){
    //
        aclrtSetDevice(i);
        HcclCommInitRootInfo(devCount, &rootInfo, global_rank, &(hccl_comms[i]));
    }
HcclGroupEnd();

Example 2: Grouping multiple collective communication operations

HcclGroupStart();
    HCCLCHECK(HcclReduceScatter(sendBuf, recvBuf, 1, HCCL_DATA_TYPE_FP32, HCCL_REDUCE_SUM, hcclComm, stream));
    HCCLCHECK(HcclAllGather(recvBuf, sendBuf, 1, HCCL_DATA_TYPE_FP32, hcclComm, stream));
HcclGroupEnd();

Example 3: Grouping multiple point-to-point communication operations

HcclGroupStart();
for(int i = 0; i < devCount; i++){
    HCCLCHECK(HcclSend(sendBuf[i], count, HCCL_DATA_TYPE_FP32, i, hcclComm, stream));
    }
for(int i = 0; i < devCount; i++){
    HCCLCHECK(HcclRecv(recvBuf[i], count, HCCL_DATA_TYPE_FP32, i, hcclComm, stream));
    }
HcclGroupEnd();