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# Build and make symbolic links for SO files
NVSHMEM_DIR=/path/to/installed/nvshmem python setup.py build
# You may modify the specific SO names according to your own platform
ln -s build/lib.linux-x86_64-cpython-38/deep_ep_cpp.cpython-38-x86_64-linux-gnu.so

# Run test cases
# NOTES: you may modify the `init_dist` function in `tests/utils.py`
# according to your own cluster settings, and launch into multiple nodes 
python tests/test_intranode.py
python tests/test_internode.py
python tests/test_low_latency.py

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NVSHMEM_DIR=/path/to/installed/nvshmem python setup.py install

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import torch
import torch.distributed as dist
from typing import List, Tuple, Optional, Union

from deep_ep import Buffer, EventOverlap

# Communication buffer (will allocate at runtime)
_buffer: Optional[Buffer] = None

# Set the number of SMs to use
# NOTES: this is a static variable
Buffer.set_num_sms(24)


# You may call this function at the framework initialization
def get_buffer(group: dist.ProcessGroup, hidden_bytes: int) -> Buffer:
    global _buffer
    
    # NOTES: you may also replace `get_*_config` with your auto-tuned results via all the tests
    num_nvl_bytes, num_rdma_bytes = 0, 0
    for config in (Buffer.get_dispatch_config(group.size()), Buffer.get_combine_config(group.size())):
        num_nvl_bytes = max(config.get_nvl_buffer_size_hint(hidden_bytes, group.size()), num_nvl_bytes)
        num_rdma_bytes = max(config.get_rdma_buffer_size_hint(hidden_bytes, group.size()), num_rdma_bytes)

    # Allocate a buffer if not existed or not enough buffer size
    if _buffer is None or _buffer.group != group or _buffer.num_nvl_bytes < num_nvl_bytes or _buffer.num_rdma_bytes < num_rdma_bytes:
        _buffer = Buffer(group, num_nvl_bytes, num_rdma_bytes)
    return _buffer


def get_hidden_bytes(x: torch.Tensor) -> int:
    t = x[0] if isinstance(x, tuple) else x
    return t.size(1) * max(t.element_size(), 2)


def dispatch_forward(x: Union[torch.Tensor, Tuple[torch.Tensor, torch.Tensor]],
                     topk_idx: torch.Tensor, topk_weights: torch.Tensor,
                     num_experts: int, previous_event: Optional[EventOverlap] = None) -> \
        Tuple[Union[torch.Tensor, Tuple[torch.Tensor, torch.Tensor]], torch.Tensor, torch.Tensor, List, Tuple, EventOverlap]:
    # NOTES: an optional `previous_event` means a CUDA event captured that you want to make it as a dependency 
    # of the dispatch kernel, it may be useful with communication-computation overlap. For more information, please
    # refer to the docs of `Buffer.dispatch`
    global _buffer

    # Calculate layout before actual dispatch
    num_tokens_per_rank, num_tokens_per_rdma_rank, num_tokens_per_expert, is_token_in_rank, previous_event = \
        _buffer.get_dispatch_layout(topk_idx, num_experts,
                                    previous_event=previous_event, async_finish=True,
                                    allocate_on_comm_stream=previous_event is not None)
    # Do MoE dispatch
    # NOTES: the CPU will wait for GPU's signal to arrive, so this is not compatible with CUDA graph
    # Unless you specify `num_worst_tokens`, but this flag is for intranode only
    # For more advanced usages, please refer to the docs of the `dispatch` function
    recv_x, recv_topk_idx, recv_topk_weights, num_recv_tokens_per_expert_list, handle, event = \
        _buffer.dispatch(x, topk_idx=topk_idx, topk_weights=topk_weights,
                         num_tokens_per_rank=num_tokens_per_rank, num_tokens_per_rdma_rank=num_tokens_per_rdma_rank,
                         is_token_in_rank=is_token_in_rank, num_tokens_per_expert=num_tokens_per_expert,
                         previous_event=previous_event, async_finish=True,
                         allocate_on_comm_stream=True)
    # For event management, please refer to the docs of the `EventOverlap` class
    return recv_x, recv_topk_idx, recv_topk_weights, num_recv_tokens_per_expert_list, handle, event


def dispatch_backward(grad_recv_x: torch.Tensor, grad_recv_topk_weights: torch.Tensor, handle: Tuple) -> \
        Tuple[torch.Tensor, torch.Tensor, EventOverlap]:
    global _buffer

    # The backward process of MoE dispatch is actually a combine
    # For more advanced usages, please refer to the docs of the `combine` function
    combined_grad_x, combined_grad_recv_topk_weights, event = \
        _buffer.combine(grad_recv_x, handle, topk_weights=grad_recv_topk_weights, async_finish=True)

    # For event management, please refer to the docs of the `EventOverlap` class
    return combined_grad_x, combined_grad_recv_topk_weights, event


def combine_forward(x: torch.Tensor, handle: Tuple, previous_event: Optional[EventOverlap] = None) -> \
        Tuple[torch.Tensor, EventOverlap]:
    global _buffer

    # Do MoE combine
    # For more advanced usages, please refer to the docs of the `combine` function
    combined_x, _, event = _buffer.combine(x, handle, async_finish=True, previous_event=previous_event,
                                           allocate_on_comm_stream=previous_event is not None)

    # For event management, please refer to the docs of the `EventOverlap` class
    return combined_x, event


def combine_backward(grad_combined_x: Union[torch.Tensor, Tuple[torch.Tensor, torch.Tensor]],
                     handle: Tuple, previous_event: Optional[EventOverlap] = None) -> \
        Tuple[Union[torch.Tensor, Tuple[torch.Tensor, torch.Tensor]], EventOverlap]:
    global _buffer

    # The backward process of MoE combine is actually a dispatch
    # For more advanced usages, please refer to the docs of the `dispatch` function
    grad_x, _, _, _, _, event = _buffer.dispatch(grad_combined_x, handle=handle, async_finish=True,
                                                 previous_event=previous_event,
                                                 allocate_on_comm_stream=previous_event is not None)

    # For event management, please refer to the docs of the `EventOverlap` class
    return grad_x, event

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import torch
import torch.distributed as dist
from typing import Tuple, Optional

from deep_ep import Buffer

# Communication buffer (will allocate at runtime)
# NOTES: there is no SM control API for the low-latency kernels
_buffer: Optional[Buffer] = None


# You may call this function at the framework initialization
def get_buffer(group: dist.ProcessGroup, num_max_dispatch_tokens_per_rank: int, hidden: int, num_experts: int) -> Buffer:
    # NOTES: the low-latency mode will consume much more space than the normal mode
    # So we recommend that `num_max_dispatch_tokens_per_rank` (the actual batch size in the decoding engine) should be less than 256
    global _buffer
    num_rdma_bytes = Buffer.get_low_latency_rdma_size_hint(num_max_dispatch_tokens_per_rank, hidden, group.size(), num_experts)

    # Allocate a buffer if not existed or not enough buffer size
    if _buffer is None or _buffer.group != group or not _buffer.low_latency_mode or _buffer.num_rdma_bytes < num_rdma_bytes:
        # NOTES: for the best performance, the QP number **must** be equal to the number of the local experts
        assert num_experts % group.size() == 0
        _buffer = Buffer(group, 0, num_rdma_bytes, low_latency_mode=True, num_qps_per_rank=num_experts // group.size())
    return _buffer


def low_latency_dispatch(hidden_states: torch.Tensor, topk_idx: torch.Tensor, num_max_dispatch_tokens_per_rank: int, num_experts: int):
    global _buffer

    # Do MoE dispatch, compatible with CUDA graph (but you may restore some buffer status once you replay)
    recv_hidden_states, recv_expert_count, handle, event, hook = \
        _buffer.low_latency_dispatch(hidden_states, topk_idx, num_max_dispatch_tokens_per_rank, num_experts,
                                     async_finish=False, return_recv_hook=True)

    # NOTES: the actual tensor will not be received only if you call `hook()`,
    # it is useful for double-batch overlapping, but **without any SM occupation**
    # If you don't want to overlap, please set `return_recv_hook=False`
    # Later, you can use our GEMM library to do the computation with this specific format
    return recv_hidden_states, recv_expert_count, handle, event, hook


def low_latency_combine(hidden_states: torch.Tensor,
                        topk_idx: torch.Tensor, topk_weights: torch.Tensor, handle: Tuple):
    global _buffer

    # Do MoE combine, compatible with CUDA graph (but you may restore some buffer status once you replay)
    combined_hidden_states, event_overlap, hook = \
        _buffer.low_latency_combine(hidden_states, topk_idx, topk_weights, handle,
                                    async_finish=False, return_recv_hook=True)

    # NOTES: the same behavior as described in the dispatch kernel
    return combined_hidden_states, event_overlap, hook

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@misc{deepep2025,
      title={DeepEP: an efficient expert-parallel communication library},
      author={Chenggang Zhao and Shangyan Zhou and Liyue Zhang and Chengqi Deng and Zhean Xu and Yuxuan Liu and Kuai Yu and Jiashi Li and Liang Zhao},
      year={2025},
      publisher = {GitHub},
      howpublished = {\url{https://github.com/deepseek-ai/DeepEP}},
}