get_rank_size

Description

Obtains the number of ranks (that is, the number of devices) in a group.

Prototype

def get_rank_size(group="hccl_world_group")

Parameters

Parameter	Input/Output	Description
group	Input	A string containing a maximum of 128 bytes, including the end character. User-defined group name. If this parameter is not set, the global hccl_world_group is passed by default.

Parameter

Input/Output

Description

group

Input

A string containing a maximum of 128 bytes, including the end character.

User-defined group name.

If this parameter is not set, the global hccl_world_group is passed by default.

Returns

Number of ranks in a group, which is of the int type.

Constraints

This API must be called after the initialization of collective communication is complete.
The caller rank must be within the range defined by the group argument passed to this API call. Otherwise, the API call fails.

After the create_group call, call this API to obtain the number of ranks in the current group.
If hccl_world_group is passed, the number of ranks in hccl_world_group is returned.

Applicability

Atlas Training Series Product

Example

The following is only a code snippet and cannot be executed. For details about how to call the HCCL Python APIs to perform collective communication, see Sample Code.

from npu_bridge.npu_init import *
create_group("myGroup", 4, [0, 1, 2, 3])  
rankSize = get_rank_size("myGroup")

Parent topic: hccl.manage.api