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"""External function interface to cuBLASlt libraries."""
import tvm
from tvm import te


def matmul(lhs, rhs, transa=False, transb=False, n=0, m=0, dtype=None):
    """Create an extern op that compute matrix mult of A and rhs with cuBLAS

    Parameters
    ----------
    lhs : Tensor
        The left matrix operand
    rhs : Tensor
        The right matrix operand
    transa : bool
        Whether transpose lhs
    transb : bool
        Whether transpose rhs

    Returns
    -------
    C : Tensor
        The result tensor.
    """
    if n == 0:
        n = lhs.shape[1] if transa else lhs.shape[0]
    if m == 0:
        m = rhs.shape[0] if transb else rhs.shape[1]
    dtype = dtype if dtype is not None else lhs.dtype
    return te.extern(
        (n, m), [lhs, rhs],
        lambda ins, outs: tvm.tir.call_packed(
            "tvm.contrib.cublaslt.matmul",
            ins[0], ins[1], outs[0], transa, transb), dtype=dtype, name="C")
