1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88

use crate::prelude::*;

/// Negates all values in `t`.
///
/// # Examples
///
/// ```rust
/// # use dfdx::prelude::*;
/// let a: Tensor1D<3> = Tensor1D::new([-2.0, 0.0, 5.0]);
/// let r = -a; // or negate(a);
/// assert_eq!(r.data(), &[2.0, 0.0, -5.0]);
/// ```
pub fn negate<T: Tensor<Dtype = f32>>(t: T) -> T {
    let result = T::NoTape::new_boxed(T::Device::map(t.data(), |v| -v));
    let (mut t, mut tape) = t.split_tape();
    let _result = result.phantom();
    tape.add_backward_op(move |grads| {
        T::Device::zip_map_assign(t.mut_data(), grads.ref_gradient(&_result), &mut |l, r| {
            *l = -r
        });
        T::Device::add_assign(grads.mut_gradient(&t), t.data());
    });
    result.put_tape(tape)
}

macro_rules! tensor_impl {
    ($typename:ident, [$($Vs:tt),*]) => {
impl<$(const $Vs: usize, )* H: Tape> std::ops::Neg for $typename<$($Vs, )* H>
{
    type Output = Self;
    /// Calls [negate()] on `self`.
    fn neg(self) -> Self::Output {
        negate(self)
    }
}
    };
}

tensor_impl!(Tensor0D, []);
tensor_impl!(Tensor1D, [M]);
tensor_impl!(Tensor2D, [M, N]);
tensor_impl!(Tensor3D, [M, N, O]);
tensor_impl!(Tensor4D, [M, N, O, P]);

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_0d_neg() {
        let a = Tensor0D::new(10.0);
        let r = -(a.trace());
        assert_eq!(r.data(), &-10.0);
        let gradients = r.backward();
        assert_eq!(gradients.ref_gradient(&a), &-1.0);
    }

    #[test]
    fn test_1d_neg() {
        let a: Tensor1D<3> = Tensor1D::new([-2.0, 0.0, 5.0]);
        let r = -(a.trace());
        assert_eq!(r.data(), &[2.0, 0.0, -5.0]);
        // NOTE: .exp() so we can make sure neg is using result grad properly
        let gradients = r.exp().mean().backward();
        assert_eq!(
            gradients.ref_gradient(&a),
            &[-2.463019, -0.33333334, -0.0022459824]
        );
    }

    #[test]
    fn test_2d_neg() {
        let a: Tensor2D<2, 3> = Tensor2D::new([[-2.0, 0.0, 5.0], [1.0, 2.0, 3.0]]);
        let r = -(a.trace());
        assert_eq!(r.data(), &[[2.0, 0.0, -5.0], [-1.0, -2.0, -3.0]]);
        let gradients = r.mean().backward();
        assert_eq!(gradients.ref_gradient(&a), &[[-1.0 / 6.0; 3]; 2]);
    }

    #[test]
    fn test_3d_neg() {
        let a: Tensor3D<4, 2, 3> = Tensor3D::ones();
        let r = -(a.trace());
        assert_eq!(r.data(), &[[[-1.0; 3]; 2]; 4]);
        let gradients = r.mean().backward();
        assert_eq!(gradients.ref_gradient(&a), &[[[-1.0 / 24.0; 3]; 2]; 4]);
    }
}