Unexpected gradient shape

[malu]

The following code panics with ndarray: could not broadcast array from shape: [2] to: [].

use autograd::ndarray::{Array, IxDyn};
use autograd::optimizers::adam::{Adam, AdamState};
use autograd::tensor::{Constant, Variable};
use std::sync::Arc;
use std::sync::RwLock;

fn main() {
    let v: Arc<RwLock<Array<f64, IxDyn>>> = autograph::ndarray_ext::into_shared(autograph::array_gen::zeros(&[]));
    let adam_state = AdamState::new(&[&v]);
    let adam = Adam::default();

    with(|graph| {
        let c = graph.constant(autograph::array_gen::ones(&[2]));
        let v = graph.variable(v.clone());

        let y = graph.reduce_sum_to_scalar(c * v);
        let grads = graph.grad(&[y], &[v]);

        let updates = adam.compute_updates(&[v], &grads, &adam_state, graph);
        graph.eval(&updates, &[]);
    })
}

It seems like grads[0] has shape [2], although y and v are scalars. I tried to find out why but didn't find an answer.

Is this a bug? Is there a workaround?

If c * v is replaced by c + v it doesn't panic, by the way.

Thanks in advance for any help you can provide!

[raskr]

@malu Sorry this is exactly a bug, and I made a patch in bingrad-hotfix branch. Could you test this?

[dependencies]
autograd = { git = "https://github.com/raskr/rust-autograd", branch = "bingrad-hotfix" }

[malu]

It works!

Thanks for checking this 👍

[raskr]

Good to hear that!
v1.1.0 will include this fix.