It seems that the subtraction operator for tensors has an issue.

[luansh01]

In the autograd.py file, to implement tensor subtraction, a sub method is defined and set rsub = sub. When a tensor is subtracted from a scalar, it obviously results in the opposite of the expected result.

def __pow__(self, other):
        if isinstance(other, Tensor):
            return needle.ops.EWisePow()(self, other)
        else:
            return needle.ops.PowerScalar(other)(self)

def __sub__(self, other):
        if isinstance(other, Tensor):
            return needle.ops.EWiseAdd()(self, needle.ops.Negate()(other))
        else:
            return needle.ops.AddScalar(-other)(self)


    __radd__ = __add__
    __rmul__ = __mul__
    __rsub__ = __sub__
    __rmatmul__ = __matmul__