Fill up a larger tensor with values and backward through it

1

I am trying to do the equivalent of tf.scatter_nd.
I have some values which I want to assign to a larger tensor and then autograd through it.
I found this issue How to achieve tf.scatter_nd in pytorch? project for copynet but it did not help me much.
I tried the following:

x = Variable(torch.zeros(5, 4), requires_grad=True)
x[idx[:, 0], idx[:, 1]] = myvalues

It complains that: a leaf Variable that requires grad has been used in an in-place operation.
I also tried it with scatter as a test and it fails as well.

x.scatter_(0, idx[:, 0], myvalues)

Is there no way in pytorch to achieve the behaviour of tf.scatter_nd?

2

I tried for fun extending autograd since it seems like this operation really doesn’t exist.
Can someone confirm me if this is correct? I tested it and it seems to correctly propagate back the gradients.

from torch.autograd import Function
class Scatter3d(Function):
    @staticmethod
    def forward(ctx, idx1, idx2, idx3, values, shape):
        # ctx is a context object that can be used to stash information
        # for backward computation
        ctx.idx1 = idx1
        ctx.idx2 = idx2
        ctx.idx3 = idx3
        outtensor = torch.zeros(shape)
        outtensor[idx1, idx2, idx3] = values
        return outtensor

    @staticmethod
    def backward(ctx, grad_output):
        # We return as many input gradients as there were arguments.
        # Gradients of non-Tensor arguments to forward must be None.
        return None, None, None, grad_output[ctx.idx1, ctx.idx2, ctx.idx3], None
3

Hello, I want to ask if your implementation of tf.scatter in pytorch is right. I want to do this operation in pytorch, but I cannot find a suitable function in pytorch.
Thank you!