问题描述：

运行torch.sum(torch.mul(users, pos_items), axis=1)时报错：

TypeError: sum() received an invalid combination of arguments - got (Tensor, axis=int), but expected one of:
 * (Tensor input)
 * (Tensor input, torch.dtype dtype)
      didn't match because some of the keywords were incorrect: axis
 * (Tensor input, tuple of ints dim, torch.dtype dtype, Tensor out)
 * (Tensor input, tuple of ints dim, bool keepdim, torch.dtype dtype, Tensor out)
 * (Tensor input, tuple of ints dim, bool keepdim, Tensor out)

其中，torch.mul函数的功能是两个维度相等的矩阵的对应位相乘，其中users和pos_items的大小都是：torch.Size([1024, 256])。

另外，torch.matmul是tensor的乘法，当输入是二维时和tensor.mm函数用法相同做普通的矩阵乘法，也能用作高维矩阵乘法。

解决方法

按照提示，axis关键字错误，经查，torch中用dim，或者直接把axis关键字去掉，即改成：

torch.sum(torch.mul(users, pos_items), dim=1)

或者

torch.sum(torch.mul(users, pos_items), 1)