target = torch.zeros(8, 8)
pos_indices = torch.tensor([
  (0, 0), (0, 2), (0, 4),
  (1, 4), (1, 6), (1, 1),
  (2, 3),
  (3, 7),
  (4, 3),
  (7, 6),
])
# Add indexes of the principal diagonal as positive indexes.
# This will be useful since we will use the BCELoss in PyTorch,
# which will expect a value for the elements on the principal
# diagonal as well.
pos_indices = torch.cat([pos_indices, torch.arange(8).reshape(8, 1).expand(-1, 2)], dim=0)
# Set the values in the target vector to 1.
target[pos_indices[:,0], pos_indices[:,1]] = 1