src/direct_product.rs

/*!
Direct products of the form $A \times B$.

TODO: This could be easily much more generic if `derive_more` could derive arithmetic
operations on references.
*/

use crate::euclidean::Euclidean;
use crate::instance::{Decomposition, DecompositionMut, Instance, InstanceMut, MyCow};
use crate::linops::AXPY;
use crate::loc::Loc;
use crate::mapping::Space;
use crate::norms::{HasDual, Norm, NormExponent, Normed, PairNorm, L2};
use crate::types::{Float, Num};
use core::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Neg, Sub, SubAssign};
use serde::{Deserialize, Serialize};
use std::clone::Clone;

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub struct Pair<A, B>(pub A, pub B);

impl<A, B> Pair<A, B> {
    pub fn new(a: A, b: B) -> Pair<A, B> {
        Pair(a, b)
    }
}

impl<A, B> From<(A, B)> for Pair<A, B> {
    #[inline]
    fn from((a, b): (A, B)) -> Pair<A, B> {
        Pair(a, b)
    }
}

impl<A, B> From<Pair<A, B>> for (A, B) {
    #[inline]
    fn from(Pair(a, b): Pair<A, B>) -> (A, B) {
        (a, b)
    }
}

// macro_rules! impl_scalarop {
//     (($a : ty, $b : ty), $field : ty, $trait : ident, $fn : ident, $refl:ident) => {
//         impl_scalarop!(@doit: $field,
//                               $trait, $fn;
//                               maybe_lifetime!($refl, &'l Pair<$a,$b>),
//                               (maybe_lifetime!($refl, &'l $a),
//                                maybe_lifetime!($refl, &'l $b));
//                               $refl);
//     };
//     (@doit: $field : ty,
//             $trait:ident, $fn:ident;
//             $self:ty, ($aself:ty, $bself:ty);
//             $refl:ident) => {
//         // Scalar as Rhs
//         impl<'l> $trait<$field>
//         for $self
//         where $aself: $trait<$field>,
//               $bself: $trait<$field> {
//             type Output = Pair<<$aself as $trait<$field>>::Output,
//                                <$bself as $trait<$field>>::Output>;
//             #[inline]
//             fn $fn(self, a : $field) -> Self::Output {
//                 Pair(maybe_ref!($refl, self.0).$fn(a),
//                      maybe_ref!($refl, self.1).$fn(a))
//             }
//         }
//     }
// }
//

macro_rules! impl_scalarop_gen {
    ($field : ty, $trait : ident, $fn : ident, $refl:ident) => {
        impl_scalarop_gen!(@doit: $field,
                              $trait, $fn;
                              maybe_lifetime!($refl, &'l Pair<A,B>),
                              (maybe_lifetime!($refl, &'l A),
                               maybe_lifetime!($refl, &'l B));
                              $refl);
    };
    (@doit: $field : ty,
            $trait:ident, $fn:ident;
            $self:ty, ($aself:ty, $bself:ty);
            $refl:ident) => {
        // Scalar as Rhs
        impl<'l, A, B> $trait<$field>
        for $self
        where $aself: $trait<$field>,
              $bself: $trait<$field> {
            type Output = Pair<<$aself as $trait<$field>>::Output,
                               <$bself as $trait<$field>>::Output>;
            #[inline]
            fn $fn(self, a : $field) -> Self::Output {
                Pair(maybe_ref!($refl, self.0).$fn(a),
                     maybe_ref!($refl, self.1).$fn(a))
            }
        }
    }
}

// Not used due to compiler overflow
#[allow(unused_macros)]
macro_rules! impl_scalarlhs_op {
    (($a : ty, $b : ty), $field : ty, $trait:ident, $fn:ident, $refr:ident) => {
        impl_scalarlhs_op!(@doit: $trait, $fn,
                                  maybe_lifetime!($refr, &'r Pair<$a,$b>),
                                  (maybe_lifetime!($refr, &'r $a),
                                   maybe_lifetime!($refr, &'r $b));
                                  $refr, $field);
    };
    (@doit: $trait:ident, $fn:ident,
            $in:ty, ($ain:ty, $bin:ty);
            $refr:ident, $field:ty) => {
        impl<'r> $trait<$in>
        for $field
        where $field : $trait<$ain>
                     + $trait<$bin> {
            type Output = Pair<<$field as $trait<$ain>>::Output,
                               <$field as $trait<$bin>>::Output>;
            #[inline]
            fn $fn(self, x : $in) -> Self::Output {
                Pair(self.$fn(maybe_ref!($refr, x.0)),
                     self.$fn(maybe_ref!($refr, x.1)))
            }
        }
    };
}

macro_rules! impl_scalar_assignop {
    (($a : ty, $b : ty), $field : ty, $trait : ident, $fn : ident) => {
        impl<'r> $trait<$field> for Pair<$a, $b>
        where
            $a: $trait<$field>,
            $b: $trait<$field>,
        {
            #[inline]
            fn $fn(&mut self, a: $field) -> () {
                self.0.$fn(a);
                self.1.$fn(a);
            }
        }
    };
}

macro_rules! impl_unary {
    ($trait:ident, $fn:ident) => {
        impl<A, B> $trait for Pair<A, B>
        where
            A: $trait,
            B: $trait,
        {
            type Output = Pair<A::Output, B::Output>;
            fn $fn(self) -> Self::Output {
                let Pair(a, b) = self;
                Pair(a.$fn(), b.$fn())
            }
        }

        impl<'a, A, B> $trait for &'a Pair<A, B>
        where
            &'a A: $trait,
            &'a B: $trait,
        {
            type Output = Pair<<&'a A as $trait>::Output, <&'a B as $trait>::Output>;
            fn $fn(self) -> Self::Output {
                let Pair(ref a, ref b) = self;
                Pair(a.$fn(), b.$fn())
            }
        }
    };
}

impl_unary!(Neg, neg);

macro_rules! impl_binary {
    ($trait:ident, $fn:ident) => {
        impl<A, B, C, D> $trait<Pair<C, D>> for Pair<A, B>
        where
            A: $trait<C>,
            B: $trait<D>,
        {
            type Output = Pair<A::Output, B::Output>;
            fn $fn(self, Pair(c, d): Pair<C, D>) -> Self::Output {
                let Pair(a, b) = self;
                Pair(a.$fn(c), b.$fn(d))
            }
        }

        impl<'a, A, B, C, D> $trait<Pair<C, D>> for &'a Pair<A, B>
        where
            &'a A: $trait<C>,
            &'a B: $trait<D>,
        {
            type Output = Pair<<&'a A as $trait<C>>::Output, <&'a B as $trait<D>>::Output>;
            fn $fn(self, Pair(c, d): Pair<C, D>) -> Self::Output {
                let Pair(ref a, ref b) = self;
                Pair(a.$fn(c), b.$fn(d))
            }
        }

        impl<'a, 'b, A, B, C, D> $trait<&'b Pair<C, D>> for &'a Pair<A, B>
        where
            &'a A: $trait<&'b C>,
            &'a B: $trait<&'b D>,
        {
            type Output = Pair<<&'a A as $trait<&'b C>>::Output, <&'a B as $trait<&'b D>>::Output>;
            fn $fn(self, Pair(ref c, ref d): &'b Pair<C, D>) -> Self::Output {
                let Pair(ref a, ref b) = self;
                Pair(a.$fn(c), b.$fn(d))
            }
        }

        impl<'b, A, B, C, D> $trait<&'b Pair<C, D>> for Pair<A, B>
        where
            A: $trait<&'b C>,
            B: $trait<&'b D>,
        {
            type Output = Pair<<A as $trait<&'b C>>::Output, <B as $trait<&'b D>>::Output>;
            fn $fn(self, Pair(ref c, ref d): &'b Pair<C, D>) -> Self::Output {
                let Pair(a, b) = self;
                Pair(a.$fn(c), b.$fn(d))
            }
        }
    };
}

macro_rules! impl_binary_mut {
    ($trait:ident, $fn:ident) => {
        impl<'a, A, B, C, D> $trait<Pair<C, D>> for Pair<A, B>
        where
            A: $trait<C>,
            B: $trait<D>,
        {
            fn $fn(&mut self, Pair(c, d): Pair<C, D>) {
                let Pair(ref mut a, ref mut b) = self;
                a.$fn(c);
                b.$fn(d);
            }
        }

        impl<'a, 'b, A, B, C, D> $trait<&'b Pair<C, D>> for Pair<A, B>
        where
            A: $trait<&'b C>,
            B: $trait<&'b D>,
        {
            fn $fn(&mut self, Pair(ref c, ref d): &'b Pair<C, D>) {
                let Pair(ref mut a, ref mut b) = self;
                a.$fn(c);
                b.$fn(d);
            }
        }
    };
}

impl_binary!(Add, add);
impl_binary!(Sub, sub);
impl_binary_mut!(AddAssign, add_assign);
impl_binary_mut!(SubAssign, sub_assign);

#[macro_export]
macro_rules! impl_pair_vectorspace_ops {
    (($a:ty, $b:ty), $field:ty) => {
        //impl_pair_vectorspace_ops!(@binary, ($a, $b), Add, add);
        //impl_pair_vectorspace_ops!(@binary, ($a, $b), Sub, sub);
        //impl_pair_vectorspace_ops!(@assign, ($a, $b), AddAssign, add_assign);
        //impl_pair_vectorspace_ops!(@assign, ($a, $b), SubAssign, sub_assign);
        // impl_pair_vectorspace_ops!(@scalar, ($a, $b), $field, Mul, mul);
        // impl_pair_vectorspace_ops!(@scalar, ($a, $b), $field, Div, div);
        // Compiler overflow
        // $(
        //     impl_pair_vectorspace_ops!(@scalar_lhs, ($a, $b), $field, $impl_scalarlhs_op, Mul, mul);
        // )*
        impl_pair_vectorspace_ops!(@scalar_assign, ($a, $b), $field, MulAssign, mul_assign);
        impl_pair_vectorspace_ops!(@scalar_assign, ($a, $b), $field, DivAssign, div_assign);
    };
    (@binary, ($a : ty, $b : ty), $trait : ident, $fn : ident) => {
        impl_binop!(($a, $b), $trait, $fn, ref, ref);
        impl_binop!(($a, $b), $trait, $fn, ref, noref);
        impl_binop!(($a, $b), $trait, $fn, noref, ref);
        impl_binop!(($a, $b), $trait, $fn, noref, noref);
    };
    (@scalar, ($a : ty, $b : ty), $field : ty, $trait : ident, $fn :ident) => {
        impl_scalarop!(($a, $b), $field, $trait, $fn, ref);
        impl_scalarop!(($a, $b), $field, $trait, $fn, noref);
    };
    (@scalar_lhs, ($a : ty, $b : ty), $field : ty, $trait : ident, $fn : ident) => {
        impl_scalarlhs_op!(($a, $b), $field, $trait, $fn, ref);
        impl_scalarlhs_op!(($a, $b), $field, $trait, $fn, noref);
    };
    (@scalar_assign, ($a : ty, $b : ty), $field : ty, $trait : ident, $fn : ident) => {
        impl_scalar_assignop!(($a, $b), $field, $trait, $fn);
    };
}

// TODO: add what we can here.
#[macro_export]
macro_rules! impl_pair_vectorspace_ops_gen {
    ($field:ty) => {
        // impl_pair_vectorspace_ops_gen!(@binary, Add, add);
        // impl_pair_vectorspace_ops_gen!(@binary, Sub, sub);
        // impl_pair_vectorspace_ops_gen!(@assign, AddAssign, add_assign);
        // impl_pair_vectorspace_ops_gen!(@assign, SubAssign, sub_assign);
        impl_pair_vectorspace_ops_gen!(@scalar, $field, Mul, mul);
        impl_pair_vectorspace_ops_gen!(@scalar, $field, Div, div);
        // impl_pair_vectorspace_ops_gen!(@scalar_assign, $field, MulAssign, mul_assign);
        // impl_pair_vectorspace_ops_gen!(@scalar_assign, $field, DivAssign, div_assign);
    };
    // (@binary, $trait : ident, $fn : ident) => {
    //     impl_binop_gen!(($a, $b), $trait, $fn, ref, ref);
    //     impl_binop_gen!(($a, $b), $trait, $fn, ref, noref);
    //     impl_binop_gen!(($a, $b), $trait, $fn, noref, ref);
    //     impl_binop_gen!(($a, $b), $trait, $fn, noref, noref);
    // };
    // (@assign, $trait : ident, $fn :ident) => {
    //     impl_assignop_gen!(($a, $b), $trait, $fn, ref);
    //     impl_assignop_gen!(($a, $b), $trait, $fn, noref);
    // };
    (@scalar, $field : ty, $trait : ident, $fn :ident) => {
        impl_scalarop_gen!($field, $trait, $fn, ref);
        impl_scalarop_gen!($field, $trait, $fn, noref);
    };
    // (@scalar_lhs, $field : ty, $trait : ident, $fn : ident) => {
    //     impl_scalarlhs_op_gen!(($a, $b), $field, $trait, $fn, ref);
    //     impl_scalarlhs_op_gen!(($a, $b), $field, $trait, $fn, noref);
    // };
    // (@scalar_assign, $field : ty, $trait : ident, $fn : ident) => {
    //     impl_scalar_assignop_gen!(($a, $b), $field, $trait, $fn);
    // };
}

impl_pair_vectorspace_ops_gen!(f32);
impl_pair_vectorspace_ops_gen!(f64);

impl_pair_vectorspace_ops!((f32, f32), f32);
impl_pair_vectorspace_ops!((f64, f64), f64);

type PairOutput<F, A, B> = Pair<<A as Euclidean<F>>::Output, <B as Euclidean<F>>::Output>;

/// We need to restrict `A` and `B` as [`Euclidean`] to have closed `Output`
/// to avoid compiler overflows that the requirement
/// ```
/// Pair<<A as Euclidean<F>>::Output, <B as Euclidean<F>>::Output> : Euclidean<F>
/// ```
/// would generate.

macro_rules! impl_euclidean {
    ($field:ty) => {
        impl<A, B> Euclidean<$field> for Pair<A, B>
        where
            A: Euclidean<$field>,
            B: Euclidean<$field>,
            PairOutput<$field, A, B>: Euclidean<$field>,
            Self: Sized
                + Mul<$field, Output = PairOutput<$field, A, B>>
                + MulAssign<$field>
                + Div<$field, Output = PairOutput<$field, A, B>>
                + DivAssign<$field>
                + Add<Self, Output = PairOutput<$field, A, B>>
                + Sub<Self, Output = PairOutput<$field, A, B>>
                + for<'b> Add<&'b Self, Output = PairOutput<$field, A, B>>
                + for<'b> Sub<&'b Self, Output = PairOutput<$field, A, B>>
                + AddAssign<Self>
                + for<'b> AddAssign<&'b Self>
                + SubAssign<Self>
                + for<'b> SubAssign<&'b Self>, //+ Neg<Output = PairOutput<$field, A, B>>,
        {
            type Output = PairOutput<$field, A, B>;

            fn dot<I: Instance<Self>>(&self, other: I) -> $field {
                let Pair(u, v) = other.decompose();
                self.0.dot(u) + self.1.dot(v)
            }

            fn norm2_squared(&self) -> $field {
                self.0.norm2_squared() + self.1.norm2_squared()
            }

            fn dist2_squared<I: Instance<Self>>(&self, other: I) -> $field {
                let Pair(u, v) = other.decompose();
                self.0.dist2_squared(u) + self.1.dist2_squared(v)
            }
        }
    };
}

impl_euclidean!(f32);
impl_euclidean!(f64);

impl<F, A, B, U, V> AXPY<F, Pair<U, V>> for Pair<A, B>
where
    U: Space,
    V: Space,
    A: AXPY<F, U>,
    B: AXPY<F, V>,
    F: Num,
    Self: MulAssign<F>,
    Pair<A, B>: MulAssign<F>,
    Pair<A::Owned, B::Owned>: AXPY<F, Pair<U, V>>,
{
    type Owned = Pair<A::Owned, B::Owned>;

    fn axpy<I: Instance<Pair<U, V>>>(&mut self, α: F, x: I, β: F) {
        let Pair(u, v) = x.decompose();
        self.0.axpy(α, u, β);
        self.1.axpy(α, v, β);
    }

    fn copy_from<I: Instance<Pair<U, V>>>(&mut self, x: I) {
        let Pair(u, v) = x.decompose();
        self.0.copy_from(u);
        self.1.copy_from(v);
    }

    fn scale_from<I: Instance<Pair<U, V>>>(&mut self, α: F, x: I) {
        let Pair(u, v) = x.decompose();
        self.0.scale_from(α, u);
        self.1.scale_from(α, v);
    }

    /// Return a similar zero as `self`.
    fn similar_origin(&self) -> Self::Owned {
        Pair(self.0.similar_origin(), self.1.similar_origin())
    }

    /// Set self to zero.
    fn set_zero(&mut self) {
        self.0.set_zero();
        self.1.set_zero();
    }
}

/// [`Decomposition`] for working with [`Pair`]s.
#[derive(Copy, Clone, Debug)]
pub struct PairDecomposition<D, Q>(D, Q);

impl<A: Space, B: Space> Space for Pair<A, B> {
    type Decomp = PairDecomposition<A::Decomp, B::Decomp>;
}

impl<A, B, D, Q> Decomposition<Pair<A, B>> for PairDecomposition<D, Q>
where
    A: Space,
    B: Space,
    D: Decomposition<A>,
    Q: Decomposition<B>,
{
    type Decomposition<'b>
        = Pair<D::Decomposition<'b>, Q::Decomposition<'b>>
    where
        Pair<A, B>: 'b;
    type Reference<'b>
        = Pair<D::Reference<'b>, Q::Reference<'b>>
    where
        Pair<A, B>: 'b;

    #[inline]
    fn lift<'b>(Pair(u, v): Self::Reference<'b>) -> Self::Decomposition<'b> {
        Pair(D::lift(u), Q::lift(v))
    }
}

impl<A, B, U, V, D, Q> Instance<Pair<A, B>, PairDecomposition<D, Q>> for Pair<U, V>
where
    A: Space,
    B: Space,
    D: Decomposition<A>,
    Q: Decomposition<B>,
    U: Instance<A, D>,
    V: Instance<B, Q>,
{
    #[inline]
    fn decompose<'b>(
        self,
    ) -> <PairDecomposition<D, Q> as Decomposition<Pair<A, B>>>::Decomposition<'b>
    where
        Self: 'b,
        Pair<A, B>: 'b,
    {
        Pair(self.0.decompose(), self.1.decompose())
    }

    #[inline]
    fn ref_instance(
        &self,
    ) -> <PairDecomposition<D, Q> as Decomposition<Pair<A, B>>>::Reference<'_> {
        Pair(self.0.ref_instance(), self.1.ref_instance())
    }

    #[inline]
    fn cow<'b>(self) -> MyCow<'b, Pair<A, B>>
    where
        Self: 'b,
    {
        MyCow::Owned(Pair(self.0.own(), self.1.own()))
    }

    #[inline]
    fn own(self) -> Pair<A, B> {
        Pair(self.0.own(), self.1.own())
    }
}

impl<'a, A, B, U, V, D, Q> Instance<Pair<A, B>, PairDecomposition<D, Q>> for &'a Pair<U, V>
where
    A: Space,
    B: Space,
    D: Decomposition<A>,
    Q: Decomposition<B>,
    U: Instance<A, D>,
    V: Instance<B, Q>,
    &'a U: Instance<A, D>,
    &'a V: Instance<B, Q>,
{
    #[inline]
    fn decompose<'b>(
        self,
    ) -> <PairDecomposition<D, Q> as Decomposition<Pair<A, B>>>::Decomposition<'b>
    where
        Self: 'b,
        Pair<A, B>: 'b,
    {
        Pair(
            D::lift(self.0.ref_instance()),
            Q::lift(self.1.ref_instance()),
        )
    }

    #[inline]
    fn ref_instance(
        &self,
    ) -> <PairDecomposition<D, Q> as Decomposition<Pair<A, B>>>::Reference<'_> {
        Pair(self.0.ref_instance(), self.1.ref_instance())
    }

    #[inline]
    fn cow<'b>(self) -> MyCow<'b, Pair<A, B>>
    where
        Self: 'b,
    {
        MyCow::Owned(self.own())
    }

    #[inline]
    fn own(self) -> Pair<A, B> {
        let Pair(ref u, ref v) = self;
        Pair(u.own(), v.own())
    }
}

impl<A, B, D, Q> DecompositionMut<Pair<A, B>> for PairDecomposition<D, Q>
where
    A: Space,
    B: Space,
    D: DecompositionMut<A>,
    Q: DecompositionMut<B>,
{
    type ReferenceMut<'b>
        = Pair<D::ReferenceMut<'b>, Q::ReferenceMut<'b>>
    where
        Pair<A, B>: 'b;
}

impl<A, B, U, V, D, Q> InstanceMut<Pair<A, B>, PairDecomposition<D, Q>> for Pair<U, V>
where
    A: Space,
    B: Space,
    D: DecompositionMut<A>,
    Q: DecompositionMut<B>,
    U: InstanceMut<A, D>,
    V: InstanceMut<B, Q>,
{
    #[inline]
    fn ref_instance_mut(
        &mut self,
    ) -> <PairDecomposition<D, Q> as DecompositionMut<Pair<A, B>>>::ReferenceMut<'_> {
        Pair(self.0.ref_instance_mut(), self.1.ref_instance_mut())
    }
}

impl<'a, A, B, U, V, D, Q> InstanceMut<Pair<A, B>, PairDecomposition<D, Q>> for &'a mut Pair<U, V>
where
    A: Space,
    B: Space,
    D: DecompositionMut<A>,
    Q: DecompositionMut<B>,
    U: InstanceMut<A, D>,
    V: InstanceMut<B, Q>,
{
    #[inline]
    fn ref_instance_mut(
        &mut self,
    ) -> <PairDecomposition<D, Q> as DecompositionMut<Pair<A, B>>>::ReferenceMut<'_> {
        Pair(self.0.ref_instance_mut(), self.1.ref_instance_mut())
    }
}

impl<F, A, B, ExpA, ExpB, ExpJ> Norm<F, PairNorm<ExpA, ExpB, ExpJ>> for Pair<A, B>
where
    F: Num,
    ExpA: NormExponent,
    ExpB: NormExponent,
    ExpJ: NormExponent,
    A: Norm<F, ExpA>,
    B: Norm<F, ExpB>,
    Loc<F, 2>: Norm<F, ExpJ>,
{
    fn norm(&self, PairNorm(expa, expb, expj): PairNorm<ExpA, ExpB, ExpJ>) -> F {
        Loc([self.0.norm(expa), self.1.norm(expb)]).norm(expj)
    }
}

impl<F: Float, A, B> Normed<F> for Pair<A, B>
where
    A: Normed<F>,
    B: Normed<F>,
{
    type NormExp = PairNorm<A::NormExp, B::NormExp, L2>;

    #[inline]
    fn norm_exponent(&self) -> Self::NormExp {
        PairNorm(self.0.norm_exponent(), self.1.norm_exponent(), L2)
    }

    #[inline]
    fn is_zero(&self) -> bool {
        self.0.is_zero() && self.1.is_zero()
    }
}

impl<F: Float, A, B> HasDual<F> for Pair<A, B>
where
    A: HasDual<F>,
    B: HasDual<F>,
{
    type DualSpace = Pair<A::DualSpace, B::DualSpace>;
}