test_add.py

import pytest
import torch
from torch.autograd import Variable
from torch_scatter import scatter_add_, scatter_add

from .utils import tensor_strs, Tensor


@pytest.mark.parametrize('str', tensor_strs)
def test_scatter_add(str):
    input = [[2, 0, 1, 4, 3], [0, 2, 1, 3, 4]]
    index = [[4, 5, 4, 2, 3], [0, 0, 2, 2, 1]]
    input = Tensor(str, input)
    index = torch.LongTensor(index)
    output = input.new(2, 6).fill_(0)
    expected_output = [[0, 0, 4, 3, 3, 0], [2, 4, 4, 0, 0, 0]]

    scatter_add_(output, index, input, dim=1)
    assert output.tolist() == expected_output

    output = scatter_add(index, input, dim=1)
    assert output.tolist() == expected_output

    output = Variable(output).fill_(0)
    index = Variable(index)
    input = Variable(input, requires_grad=True)
    scatter_add_(output, index, input, dim=1)

    grad_output = [[0, 1, 2, 3, 4, 5], [0, 1, 2, 3, 4, 5]]
    grad_output = Tensor(str, grad_output)

    output.backward(grad_output)
    assert index.data.tolist() == input.grad.data.tolist()