dfdx 0.9.0

Ergonomic auto differentiation in Rust, with pytorch like apis.
Documentation 
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use crate::prelude::*;

/// The main tensor trait. A tensor consists of mainly 1. an array, 2. a device, 3. a unique id.
pub trait Tensor:
    HasArrayType + HasArrayData + HasDevice + CanUpdateWithGradients + HasUniqueId + IntoPhantom
{
    /// The [Tape] this tensor owns.
    type Tape: Tape;

    /// This tensor but with [NoneTape].
    type NoTape: 'static
        + Tensor<Array = Self::Array, Dtype = Self::Dtype, Tape = NoneTape, NoTape = Self::NoTape>
        // NOTE: we only want to be able to create NoneTape tensors
        + TensorCreator
        // NOTE: Adding this restriction means we can put the tape from Self into the Self::NoTape
        + PutTape<Self::Tape, Output = Self>
        + Clone;

    /// This tensor but with [OwnedTape]
    type OwnedTape: 'static
        + Tensor<
            Array = Self::Array,
            Dtype = Self::Dtype,
            Tape = OwnedTape,
            OwnedTape = Self::OwnedTape,
        >;

    /// Removes whatever Tape this tensor has and returns itself without a tape.
    fn split_tape(self) -> (Self::NoTape, Self::Tape);

    /// Clones the data & [UniqueId] of this tensor and returns something with [NoneTape].
    fn duplicate(&self) -> Self::NoTape;
}

macro_rules! tensor_impl {
    ($struct:ident, [$($Vs:tt),*]) => {
impl<$(const $Vs: usize, )* H: Tape> Tensor for $struct<$($Vs, )* H> {
    type Tape = H;
    type NoTape = $struct<$($Vs, )* NoneTape>;
    type OwnedTape = $struct<$($Vs, )* OwnedTape>;

    fn split_tape(self) -> (Self::NoTape, Self::Tape) {
        (
            Self::NoTape { id: self.id, data: self.data, tape: Default::default() },
            self.tape,
        )
    }

    fn duplicate(&self) -> Self::NoTape {
        Self::NoTape {
            id: self.id,
            data: self.data.clone(),
            tape: Default::default(),
        }
    }
}

impl<$(const $Vs: usize, )* H: Clone> Clone for $struct<$($Vs, )* H> {
    /// Clones the underlying data and tape. **Creates a new [UniqueId].**
    fn clone(&self) -> Self {
        Self {
            id: unique_id(),
            data: self.data.clone(),
            tape: self.tape.clone(),
        }
    }
}
    };
}

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_ids_with_duplicate() {
        let t1: Tensor1D<32> = TensorCreator::zeros();
        let t2: Tensor1D<32, NoneTape> = t1.duplicate();
        assert_eq!(t1.id, t2.id);
    }

    #[test]
    fn test_ids_with_clone() {
        let t1: Tensor1D<32> = TensorCreator::zeros();
        let t2: Tensor1D<32, NoneTape> = t1.clone();
        assert_ne!(t1.id, t2.id);
    }

    #[test]
    fn test_ids_with_split_and_put() {
        let t1: Tensor1D<32> = TensorCreator::zeros();
        let t1_id = t1.id;
        let (t2, tape) = t1.split_tape();
        assert_eq!(t2.id, t1_id);
        let t3 = t2.put_tape(tape);
        assert_eq!(t3.id, t1_id);
    }
}