Power 8 machine torch.remainder RuntimeError: the derivative for 'other' is not implemented

I have a customized autograd mod function

import torch
from torch.autograd import Function, Variable

class ModFunction(Function):
    # Note that both forward and backward are @staticmethods
    def forward(ctx, x, y):
        ctx.save_for_backward(x, y)
        output = torch.remainder(x, y)
        return output
    def backward(ctx, grad_output):
        x, y = ctx.saved_variables
        grad_x = grad_output.clone()
        grad_y = (torch.mean(grad_output*( -1 * (x / y).floor()), dim = 0))
        return grad_x, grad_y

when i run it on Power 8 machine. torch.remainder throw RuntimeError: the derivative for ‘other’ is not implemented. Please help! Thanks!