import torch

from vllm_ascend.utils import enable_custom_op

enable_custom_op()

DEFAULT_ATOL = 1e-3
DEFAULT_RTOL = 1e-3


def bgmv_shrink_cpu_impl(x: torch.Tensor, w: torch.Tensor,
                         indices: torch.Tensor, y: torch.tensor,
                         scaling: float) -> torch.Tensor:
    W = w[indices, :, :].transpose(-1, -2).to(torch.float32)
    z = torch.bmm(x.unsqueeze(1).to(torch.float32), W).squeeze()
    y[:, :] += z * scaling
    return y


@torch.inference_mode()
def test_bgmv_shrink() -> None:
    B = 1
    x = torch.randn([B, 128], dtype=torch.float16)
    w = torch.randn([64, 16, 128], dtype=torch.float16)
    indices = torch.zeros([B], dtype=torch.int64)
    y = torch.zeros([B, 16])

    x_npu = x.npu()
    w_npu = w.npu()
    indices_npu = indices.npu()
    y_npu = y.npu()

    y = bgmv_shrink_cpu_impl(x, w, indices, y, 0.5)
    torch.ops._C.bgmv_shrink(x_npu, w_npu, indices_npu, y_npu, 0.5)

    # Compare the results.
    torch.testing.assert_close(y_npu.cpu(),
                               y,
                               atol=DEFAULT_ATOL,
                               rtol=DEFAULT_RTOL)