/
VectorBundle.jl
1117 lines (950 loc) · 36.8 KB
/
VectorBundle.jl
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"""
VectorSpaceType
Abstract type for tangent spaces, cotangent spaces, their tensor products,
exterior products, etc.
Every vector space `fiber` is supposed to provide:
* a method of constructing vectors,
* basic operations: addition, subtraction, multiplication by a scalar
and negation (unary minus),
* [`zero_vector!(fiber, X, p)`](@ref) to construct zero vectors at point `p`,
* `allocate(X)` and `allocate(X, T)` for vector `X` and type `T`,
* `copyto!(X, Y)` for vectors `X` and `Y`,
* `number_eltype(v)` for vector `v`,
* [`vector_space_dimension(::VectorBundleFibers{<:typeof(fiber)}) where fiber`](@ref).
Optionally:
* inner product via `inner` (used to provide Riemannian metric on vector
bundles),
* [`flat`](@ref) and [`sharp`](@ref),
* `norm` (by default uses `inner`),
* [`project`](@ref) (for embedded vector spaces),
* [`representation_size`](@ref) (if support for [`ProductArray`](@ref) is desired),
* broadcasting for basic operations.
"""
abstract type VectorSpaceType end
struct TangentSpaceType <: VectorSpaceType end
struct CotangentSpaceType <: VectorSpaceType end
TCoTSpaceType = Union{TangentSpaceType,CotangentSpaceType}
const TangentSpace = TangentSpaceType()
const CotangentSpace = CotangentSpaceType()
"""
TensorProductType(spaces::VectorSpaceType...)
Vector space type corresponding to the tensor product of given vector space
types.
"""
struct TensorProductType{TS<:Tuple} <: VectorSpaceType
spaces::TS
end
TensorProductType(spaces::VectorSpaceType...) = TensorProductType{typeof(spaces)}(spaces)
"""
VectorBundleFibers(fiber::VectorSpaceType, M::Manifold)
Type representing a family of vector spaces (fibers) of a vector bundle over `M`
with vector spaces of type `fiber`. In contrast with `VectorBundle`, operations
on `VectorBundleFibers` expect point-like and vector-like parts to be
passed separately instead of being bundled together. It can be thought of
as a representation of vector spaces from a vector bundle but without
storing the point at which a vector space is attached (which is specified
separately in various functions).
"""
struct VectorBundleFibers{TVS<:VectorSpaceType,TM<:Manifold}
fiber::TVS
manifold::TM
end
const TangentBundleFibers{M} = VectorBundleFibers{TangentSpaceType,M} where {M<:Manifold}
TangentBundleFibers(M::Manifold) = VectorBundleFibers(TangentSpace, M)
const CotangentBundleFibers{M} =
VectorBundleFibers{CotangentSpaceType,M} where {M<:Manifold}
CotangentBundleFibers(M::Manifold) = VectorBundleFibers(CotangentSpace, M)
"""
VectorSpaceAtPoint{
𝔽,
TFiber<:VectorBundleFibers{<:VectorSpaceType,<:Manifold{𝔽}},
TX,
} <: Manifold{𝔽}
A vector space at a point `p` on the manifold.
This is modelled using [`VectorBundleFibers`](@ref) with only a vector-like part
and fixing the point-like part to be just `p`.
This vector space itself is also a `manifold`. Especially, it's flat and hence isometric
to the [`Euclidean`](@ref) manifold.
# Constructor
VectorSpaceAtPoint(fiber::VectorBundleFibers, p)
A vector space (fiber type `fiber` of a vector bundle) at point `p` from
the manifold `fiber.manifold`.
"""
struct VectorSpaceAtPoint{
𝔽,
TFiber<:VectorBundleFibers{<:VectorSpaceType,<:Manifold{𝔽}},
TX,
} <: Manifold{𝔽}
fiber::TFiber
point::TX
end
const TangentSpaceAtPoint{M} =
VectorSpaceAtPoint{𝔽,TangentBundleFibers{M}} where {𝔽,M<:Manifold{𝔽}}
"""
TangentSpaceAtPoint(M::Manifold, p)
Return an object of type [`VectorSpaceAtPoint`](@ref) representing tangent
space at `p` on the [`Manifold`](@ref) `M`.
"""
TangentSpaceAtPoint(M::Manifold, p) = VectorSpaceAtPoint(TangentBundleFibers(M), p)
"""
TangentSpace(M::Manifold, p)
Return a [`TangentSpaceAtPoint`](@ref) representing tangent space at `p` on the [`Manifold`](@ref) `M`.
"""
TangentSpace(M::Manifold, p) = VectorSpaceAtPoint(TangentBundleFibers(M), p)
const CotangentSpaceAtPoint{M} =
VectorSpaceAtPoint{𝔽,CotangentBundleFibers{M}} where {𝔽,M<:Manifold{𝔽}}
"""
CotangentSpaceAtPoint(M::Manifold, p)
Return an object of type [`VectorSpaceAtPoint`](@ref) representing cotangent
space at `p`.
"""
CotangentSpaceAtPoint(M::Manifold, p) = VectorSpaceAtPoint(CotangentBundleFibers(M), p)
"""
VectorBundleVectorTransport(
method_point::AbstractVectorTransportMethod,
method_vector::AbstractVectorTransportMethod,
)
Vector transport type on [`VectorBundle`](@ref). `method_point` is used for vector transport
of the point part and `method_vector` is used for transport of the vector part
"""
struct VectorBundleVectorTransport{
TMP<:AbstractVectorTransportMethod,
TMV<:AbstractVectorTransportMethod,
} <: AbstractVectorTransportMethod
method_point::TMP
method_vector::TMV
end
"""
VectorBundle{𝔽,TVS<:VectorSpaceType,TM<:Manifold{𝔽}} <: Manifold{𝔽}
Vector bundle on a [`Manifold`](@ref) `M` of type [`VectorSpaceType`](@ref).
# Constructor
VectorBundle(M::Manifold, type::VectorSpaceType)
"""
struct VectorBundle{
𝔽,
TVS<:VectorSpaceType,
TM<:Manifold{𝔽},
TVT<:VectorBundleVectorTransport,
} <: Manifold{𝔽}
type::TVS
manifold::TM
fiber::VectorBundleFibers{TVS,TM}
vector_transport::TVT
end
function VectorBundle(
fiber::TVS,
M::TM,
vtm::VectorBundleVectorTransport,
) where {TVS<:VectorSpaceType,TM<:Manifold{𝔽}} where {𝔽}
return VectorBundle{𝔽,TVS,TM,typeof(vtm)}(fiber, M, VectorBundleFibers(fiber, M), vtm)
end
function VectorBundle(fiber::VectorSpaceType, M::Manifold)
vtmm = vector_bundle_transport(fiber, M)
vtbm = VectorBundleVectorTransport(vtmm, vtmm)
return VectorBundle(fiber, M, vtbm)
end
const TangentBundle{𝔽,M} = VectorBundle{𝔽,TangentSpaceType,M} where {𝔽,M<:Manifold{𝔽}}
TangentBundle(M::Manifold) = VectorBundle(TangentSpace, M)
function TangentBundle(M::Manifold, vtm::VectorBundleVectorTransport)
return VectorBundle(TangentSpace, M, vtm)
end
const CotangentBundle{𝔽,M} = VectorBundle{𝔽,CotangentSpaceType,M} where {𝔽,M<:Manifold{𝔽}}
CotangentBundle(M::Manifold) = VectorBundle(CotangentSpace, M)
function CotangentBundle(M::Manifold, vtm::VectorBundleVectorTransport)
return VectorBundle(CotangentSpace, M, vtm)
end
"""
FVector(type::VectorSpaceType, data)
Decorator indicating that the vector `data` is from a fiber of a vector bundle
of type `type`.
"""
struct FVector{TType<:VectorSpaceType,TData}
type::TType
data::TData
end
const TFVector = FVector{TangentSpaceType}
const CoTFVector = FVector{CotangentSpaceType}
struct VectorBundleBasisData{BBasis<:CachedBasis,TBasis<:CachedBasis}
base_basis::BBasis
vec_basis::TBasis
end
Base.:+(X::FVector, Y::FVector) = FVector(X.type, X.data + Y.data)
Base.:-(X::FVector, Y::FVector) = FVector(X.type, X.data - Y.data)
Base.:-(X::FVector) = FVector(X.type, -X.data)
Base.:*(a::Number, X::FVector) = FVector(X.type, a * X.data)
function Base.copyto!(X::FVector, Y::FVector)
copyto!(X.data, Y.data)
return X
end
base_manifold(B::VectorBundleFibers) = base_manifold(B.manifold)
base_manifold(B::VectorSpaceAtPoint) = base_manifold(B.fiber)
base_manifold(B::VectorBundle) = base_manifold(B.manifold)
"""
bundle_projection(B::VectorBundle, x::ProductRepr)
Projection of point `p` from the bundle `M` to the base manifold.
Returns the point on the base manifold `B.manifold` at which the vector part
of `p` is attached.
"""
bundle_projection(B::VectorBundle, p) = submanifold_component(B.manifold, p, Val(1))
"""
distance(B::VectorBundleFibers, p, X, Y)
Distance between vectors `X` and `Y` from the vector space at point `p`
from the manifold `B.manifold`, that is the base manifold of `M`.
"""
distance(B::VectorBundleFibers, p, X, Y) = norm(B, p, X - Y)
@doc raw"""
distance(B::VectorBundle, p, q)
Distance between points $x$ and $y$ from the
vector bundle `B` over manifold `B.fiber` (denoted $\mathcal M$).
Notation:
* The point $p = (x_p, V_p)$ where $x_p ∈ \mathcal M$ and $V_p$ belongs to the
fiber $F=π^{-1}(\{x_p\})$ of the vector bundle $B$ where $π$ is the
canonical projection of that vector bundle $B$.
Similarly, $q = (x_q, V_q)$.
The distance is calculated as
$d_B(x, y) = \sqrt{d_M(x_p, x_q)^2 + d_F(V_p, V_{q←p})^2}$
where $d_\mathcal M$ is the distance on manifold $\mathcal M$, $d_F$ is the distance
between two vectors from the fiber $F$ and $V_{q←p}$ is the result
of parallel transport of vector $V_q$ to point $x_p$. The default
behavior of [`vector_transport_to`](@ref) is used to compute the vector
transport.
"""
function distance(B::VectorBundle, p, q)
xp, Vp = submanifold_components(B.manifold, p)
xq, Vq = submanifold_components(B.manifold, q)
dist_man = distance(B.manifold, xp, xq)
vy_x = vector_transport_to(B.manifold, xq, Vq, xp, B.vector_transport.method_point)
dist_vec = distance(B.fiber, xp, Vp, vy_x)
return sqrt(dist_man^2 + dist_vec^2)
end
"""
distance(M::TangentSpaceAtPoint, p, q)
Distance between vectors `p` and `q` from the vector space `M`. It is calculated as the norm
of their difference.
"""
function distance(M::TangentSpaceAtPoint, p, q)
return norm(M.fiber.manifold, M.point, q - p)
end
function number_eltype(::Type{FVector{TType,TData}}) where {TType<:VectorSpaceType,TData}
return number_eltype(TData)
end
number_eltype(v::FVector) = number_eltype(v.data)
function embed!(M::TangentSpaceAtPoint, q, p)
return embed!(M.fiber.manifold, q, M.point, p)
end
function embed!(M::TangentSpaceAtPoint, Y, p, X)
return embed!(M.fiber.manifold, Y, M.point, X)
end
@doc raw"""
exp(B::VectorBundle, p, X)
Exponential map of tangent vector $X$ at point $p$ from
vector bundle `B` over manifold `B.fiber` (denoted $\mathcal M$).
Notation:
* The point $p = (x_p, V_p)$ where $x_p ∈ \mathcal M$ and $V_p$ belongs to the
fiber $F=π^{-1}(\{x_p\})$ of the vector bundle $B$ where $π$ is the
canonical projection of that vector bundle $B$.
* The tangent vector $X = (V_{X,M}, V_{X,F}) ∈ T_pB$ where
$V_{X,M}$ is a tangent vector from the tangent space $T_{x_p}\mathcal M$ and
$V_{X,F}$ is a tangent vector from the tangent space $T_{V_p}F$ (isomorphic to $F$).
The exponential map is calculated as
$\exp_p(X) = (\exp_{x_p}(V_{X,M}), V_{\exp})$
where $V_{\exp}$ is the result of vector transport of $V_p + V_{X,F}$
to the point $\exp_{x_p}(V_{X,M})$.
The sum $V_p + V_{X,F}$ corresponds to the exponential map in the vector space $F$.
"""
exp(::VectorBundle, ::Any, ::Any)
@doc raw"""
exp(M::TangentSpaceAtPoint, p, X)
Exponential map of tangent vectors `X` and `p` from the tangent space `M`. It is
calculated as their sum.
"""
exp(::TangentSpaceAtPoint, ::Any, ::Any)
function exp!(B::VectorBundle, q, p, X)
xp, Xp = submanifold_components(B.manifold, p)
xq, Xq = submanifold_components(B.manifold, q)
VXM, VXF = submanifold_components(B.manifold, X)
exp!(B.manifold, xq, xp, VXM)
vector_transport_to!(B.manifold, Xq, xp, Xp + VXF, xq, B.vector_transport.method_point)
return q
end
function exp!(M::TangentSpaceAtPoint, q, p, X)
copyto!(q, p + X)
return q
end
@doc raw"""
flat(M::Manifold, p, X::FVector)
Compute the flat isomorphism (one of the musical isomorphisms) of tangent vector `X`
from the vector space of type `M` at point `p` from the underlying [`Manifold`](@ref).
The function can be used for example to transform vectors
from the tangent bundle to vectors from the cotangent bundle
$♭ : T\mathcal M → T^{*}\mathcal M$
"""
function flat(M::Manifold, p, X::FVector)
ξ = allocate_result(M, flat, X, p)
return flat!(M, ξ, p, X)
end
function flat!(M::Manifold, ξ::FVector, p, X::FVector)
return error(
"flat! not implemented for vector bundle fibers space " *
"of type $(typeof(M)), vector of type $(typeof(ξ)), point of " *
"type $(typeof(p)) and vector of type $(typeof(X)).",
)
end
@decorator_transparent_signature flat!(
M::AbstractDecoratorManifold,
ξ::CoTFVector,
p,
X::TFVector,
)
function get_basis(M::VectorBundle, p, B::AbstractBasis)
xp1 = submanifold_component(p, Val(1))
base_basis = get_basis(M.manifold, xp1, B)
vec_basis = get_basis(M.fiber, xp1, B)
return CachedBasis(B, VectorBundleBasisData(base_basis, vec_basis))
end
function get_basis(M::VectorBundle, p, B::CachedBasis)
return invoke(get_basis, Tuple{Manifold,Any,CachedBasis}, M, p, B)
end
function get_basis(M::TangentSpaceAtPoint, p, B::CachedBasis)
return invoke(get_basis, Tuple{Manifold,Any,CachedBasis}, M.fiber.manifold, M.point, B)
end
function get_basis(M::VectorBundle, p, B::DiagonalizingOrthonormalBasis)
xp1 = submanifold_component(p, Val(1))
bv1 = DiagonalizingOrthonormalBasis(submanifold_component(B.frame_direction, Val(1)))
b1 = get_basis(M.manifold, xp1, bv1)
bv2 = DiagonalizingOrthonormalBasis(submanifold_component(B.frame_direction, Val(2)))
b2 = get_basis(M.fiber, xp1, bv2)
return CachedBasis(B, VectorBundleBasisData(b1, b2))
end
for BT in [
DefaultOrthonormalBasis,
ProjectedOrthonormalBasis{:gram_schmidt,ℝ},
ProjectedOrthonormalBasis{:svd,ℝ},
]
eval(quote
@invoke_maker 3 AbstractBasis get_basis(M::VectorBundle, p, B::$BT)
end)
eval(quote
@invoke_maker 3 AbstractBasis get_basis(M::TangentSpaceAtPoint, p, B::$BT)
end)
end
function get_basis(M::TangentBundleFibers, p, B::AbstractBasis)
return get_basis(M.manifold, p, B)
end
function get_basis(M::TangentSpaceAtPoint, p, B::AbstractBasis)
return get_basis(M.fiber.manifold, M.point, B)
end
function get_coordinates!(M::VectorBundle, Y, p, X, B::AbstractBasis)
px, Vx = submanifold_components(M.manifold, p)
VXM, VXF = submanifold_components(M.manifold, X)
n = manifold_dimension(M.manifold)
get_coordinates!(M.manifold, view(Y, 1:n), px, VXM, B)
get_coordinates!(M.fiber, view(Y, (n + 1):length(Y)), px, VXF, B)
return Y
end
function get_coordinates!(
M::VectorBundle,
Y,
p,
X,
B::CachedBasis{𝔽,<:AbstractBasis{𝔽},<:VectorBundleBasisData},
) where {𝔽}
px, Vx = submanifold_components(M.manifold, p)
VXM, VXF = submanifold_components(M.manifold, X)
n = manifold_dimension(M.manifold)
get_coordinates!(M.manifold, view(Y, 1:n), px, VXM, B.data.base_basis)
get_coordinates!(M.fiber, view(Y, (n + 1):length(Y)), px, VXF, B.data.vec_basis)
return Y
end
for BT in [
DefaultBasis,
DefaultOrthogonalBasis,
DefaultOrthonormalBasis,
ProjectedOrthonormalBasis{:gram_schmidt,ℝ},
ProjectedOrthonormalBasis{:svd,ℝ},
VeeOrthogonalBasis,
]
eval(
quote
@invoke_maker 5 AbstractBasis get_coordinates!(
M::VectorBundle,
Y,
p,
X,
B::$BT,
)
end,
)
eval(
quote
@invoke_maker 5 AbstractBasis get_coordinates!(
M::TangentSpaceAtPoint,
Y,
p,
X,
B::$BT,
)
end,
)
end
function get_coordinates!(M::VectorBundle, Y, p, X, B::CachedBasis)
return error("get_coordinates! called on $M with an incorrect CachedBasis. Expected a CachedBasis with VectorBundleBasisData, given $B")
end
function get_coordinates!(M::TangentSpaceAtPoint, Y, p, X, B::CachedBasis)
return get_coordinates!(M.fiber.manifold, Y, M.point, X, B)
end
function get_coordinates!(
M::TangentBundleFibers,
Y,
p,
X,
B::ManifoldsBase.all_uncached_bases,
)
return get_coordinates!(M.manifold, Y, p, X, B)
end
function get_coordinates!(
M::TangentSpaceAtPoint,
Y,
p,
X,
B::ManifoldsBase.all_uncached_bases,
)
return get_coordinates!(M.fiber.manifold, Y, M.point, X, B)
end
function get_vector!(M::VectorBundle, Y, p, X, B::DefaultOrthonormalBasis)
n = manifold_dimension(M.manifold)
xp1 = submanifold_component(p, Val(1))
get_vector!(M.manifold, submanifold_component(Y, Val(1)), xp1, X[1:n], B)
get_vector!(M.fiber, submanifold_component(Y, Val(2)), xp1, X[(n + 1):end], B)
return Y
end
function get_vector!(
M::VectorBundle,
Y,
p,
X,
B::CachedBasis{𝔽,<:AbstractBasis{𝔽},<:VectorBundleBasisData},
) where {𝔽}
n = manifold_dimension(M.manifold)
xp1 = submanifold_component(p, Val(1))
get_vector!(
M.manifold,
submanifold_component(Y, Val(1)),
xp1,
X[1:n],
B.data.base_basis,
)
get_vector!(
M.fiber,
submanifold_component(Y, Val(2)),
xp1,
X[(n + 1):end],
B.data.vec_basis,
)
return Y
end
function get_vector!(M::TangentBundleFibers, Y, p, X, B::ManifoldsBase.all_uncached_bases)
return get_vector!(M.manifold, Y, p, X, B)
end
function get_vector!(M::TangentSpaceAtPoint, Y, p, X, B::ManifoldsBase.all_uncached_bases)
return get_vector!(M.fiber.manifold, Y, M.point, X, B)
end
for BT in [
DefaultBasis,
DefaultOrthogonalBasis,
DefaultOrthonormalBasis,
ProjectedOrthonormalBasis{:gram_schmidt,ℝ},
ProjectedOrthonormalBasis{:svd,ℝ},
VeeOrthogonalBasis,
]
eval(
quote
@invoke_maker 5 AbstractBasis get_vector!(
M::TangentSpaceAtPoint,
Y,
p,
X,
B::$BT,
)
end,
)
end
function get_vector!(M::TangentSpaceAtPoint, Y, p, X, B::CachedBasis)
return get_vector!(M.fiber.manifold, Y, M.point, X, B)
end
function get_vectors(
M::VectorBundle,
p,
B::CachedBasis{𝔽,<:AbstractBasis{𝔽},<:VectorBundleBasisData},
) where {𝔽}
xp1 = submanifold_component(p, Val(1))
zero_m = zero_tangent_vector(M.manifold, xp1)
zero_f = zero_vector(M.fiber, xp1)
vs = typeof(ProductRepr(zero_m, zero_f))[]
for bv in get_vectors(M.manifold, xp1, B.data.base_basis)
push!(vs, ProductRepr(bv, zero_f))
end
for bv in get_vectors(M.fiber, xp1, B.data.vec_basis)
push!(vs, ProductRepr(zero_m, bv))
end
return vs
end
function get_vectors(M::VectorBundleFibers, p, B::CachedBasis)
return get_vectors(M.manifold, p, B)
end
function get_vectors(M::TangentSpaceAtPoint, p, B::CachedBasis)
return get_vectors(M.fiber.manifold, M.point, B)
end
Base.@propagate_inbounds Base.getindex(x::FVector, i) = getindex(x.data, i)
"""
getindex(p::ProductRepr, M::VectorBundle, s::Symbol)
p[M::VectorBundle, s]
Access the element(s) at index `s` of a point `p` on a [`VectorBundle`](@ref) `M` by
using the symbols `:point` and `:vector` for the base and vector component, respectively.
"""
@inline function Base.getindex(p::ProductRepr, M::VectorBundle, s::Symbol)
(s === :point) && return submanifold_component(M, p, Val(1))
(s === :vector) && return submanifold_component(M, p, Val(2))
return throw(DomainError(s, "unknown component $s on $M."))
end
@doc raw"""
injectivity_radius(M::TangentSpaceAtPoint)
Return the injectivity radius on the [`TangentSpaceAtPoint`](@ref) `M`, which is $∞$.
"""
injectivity_radius(::TangentSpaceAtPoint) = Inf
"""
inner(B::VectorBundleFibers, p, X, Y)
Inner product of vectors `X` and `Y` from the vector space of type `B.fiber`
at point `p` from manifold `B.manifold`.
"""
function inner(B::VectorBundleFibers, p, X, Y)
return error(
"inner not defined for vector space family of type $(typeof(B)), " *
"point of type $(typeof(p)) and " *
"vectors of types $(typeof(X)) and $(typeof(Y)).",
)
end
inner(B::VectorBundleFibers{<:TangentSpaceType}, p, X, Y) = inner(B.manifold, p, X, Y)
function inner(B::VectorBundleFibers{<:CotangentSpaceType}, p, X, Y)
return inner(
B.manifold,
p,
sharp(B.manifold, p, FVector(CotangentSpace, X)).data,
sharp(B.manifold, p, FVector(CotangentSpace, Y)).data,
)
end
@doc raw"""
inner(B::VectorBundle, p, X, Y)
Inner product of tangent vectors `X` and `Y` at point `p` from the
vector bundle `B` over manifold `B.fiber` (denoted $\mathcal M$).
Notation:
* The point $p = (x_p, V_p)$ where $x_p ∈ \mathcal M$ and $V_p$ belongs to the
fiber $F=π^{-1}(\{x_p\})$ of the vector bundle $B$ where $π$ is the
canonical projection of that vector bundle $B$.
* The tangent vector $v = (V_{X,M}, V_{X,F}) ∈ T_{x}B$ where
$V_{X,M}$ is a tangent vector from the tangent space $T_{x_p}\mathcal M$ and
$V_{X,F}$ is a tangent vector from the tangent space $T_{V_p}F$ (isomorphic to $F$).
Similarly for the other tangent vector $w = (V_{Y,M}, V_{Y,F}) ∈ T_{x}B$.
The inner product is calculated as
$⟨X, Y⟩_p = ⟨V_{X,M}, V_{Y,M}⟩_{x_p} + ⟨V_{X,F}, V_{Y,F}⟩_{V_p}.$
"""
function inner(B::VectorBundle, p, X, Y)
px, Vx = submanifold_components(B.manifold, p)
VXM, VXF = submanifold_components(B.manifold, X)
VYM, VYF = submanifold_components(B.manifold, Y)
# for tangent bundle Vx is discarded by the method of inner for TangentSpaceAtPoint
# and px is actually used as the base point
return inner(B.manifold, px, VXM, VYM) +
inner(VectorSpaceAtPoint(B.fiber, px), Vx, VXF, VYF)
end
"""
inner(M::TangentSpaceAtPoint, p, X, Y)
Inner product of vectors `X` and `Y` from the tangent space at `M`.
"""
function inner(M::TangentSpaceAtPoint, p, X, Y)
return inner(M.fiber.manifold, M.point, X, Y)
end
function Base.isapprox(B::VectorBundle, p, q; kwargs...)
xp, Vp = submanifold_components(B.manifold, p)
xq, Vq = submanifold_components(B.manifold, q)
return isapprox(B.manifold, xp, xq; kwargs...) &&
isapprox(VectorSpaceAtPoint(B.fiber, xp), Vp, Vq; kwargs...)
end
function Base.isapprox(B::VectorBundle, p, X, Y; kwargs...)
px, Vx = submanifold_components(B.manifold, p)
VXM, VXF = submanifold_components(B.manifold, X)
VYM, VYF = submanifold_components(B.manifold, Y)
return isapprox(B.manifold, VXM, VYM; kwargs...) &&
isapprox(VectorSpaceAtPoint(B.fiber, px), VXF, VYF; kwargs...)
end
function Base.isapprox(M::TangentSpaceAtPoint, X, Y; kwargs...)
return isapprox(M.fiber.manifold, M.point, X, Y; kwargs...)
end
@doc raw"""
log(B::VectorBundle, p, q)
Logarithmic map of the point `y` at point `p` from
vector bundle `B` over manifold `B.fiber` (denoted $\mathcal M$).
Notation:
* The point $p = (x_p, V_p)$ where $x_p ∈ \mathcal M$ and $V_p$ belongs to the
fiber $F=π^{-1}(\{x_p\})$ of the vector bundle $B$ where $π$ is the
canonical projection of that vector bundle $B$.
Similarly, $q = (x_q, V_q)$.
The logarithmic map is calculated as
$\log_p q = (\log_{x_p}(x_q), V_{\log} - V_p)$
where $V_{\log}$ is the result of vector transport of $V_q$ to the point $x_p$.
The difference $V_{\log} - V_p$ corresponds to the logarithmic map in the vector space $F$.
"""
log(::VectorBundle, ::Any...)
"""
log(M::TangentSpaceAtPoint, p, q)
Logarithmic map on the tangent space manifold `M`, calculated as the difference of tangent
vectors `q` and `p` from `M`.
"""
log(::TangentSpaceAtPoint, ::Any...)
function log!(B::VectorBundle, X, p, q)
px, Vx = submanifold_components(B.manifold, p)
py, Vy = submanifold_components(B.manifold, q)
VXM, VXF = submanifold_components(B.manifold, X)
log!(B.manifold, VXM, px, py)
vector_transport_to!(B.manifold, VXF, py, Vy, px, B.vector_transport.method_vector)
copyto!(VXF, VXF - Vx)
return X
end
function log!(::TangentSpaceAtPoint, X, p, q)
copyto!(X, q - p)
return X
end
function manifold_dimension(B::VectorBundle)
return manifold_dimension(B.manifold) + vector_space_dimension(B.fiber)
end
function manifold_dimension(M::VectorSpaceAtPoint)
return vector_space_dimension(M.fiber)
end
"""
norm(B::VectorBundleFibers, p, q)
Norm of the vector `X` from the vector space of type `B.fiber`
at point `p` from manifold `B.manifold`.
"""
LinearAlgebra.norm(B::VectorBundleFibers, p, X) = sqrt(inner(B, p, X, X))
LinearAlgebra.norm(B::VectorBundleFibers{<:TangentSpaceType}, p, X) = norm(B.manifold, p, X)
LinearAlgebra.norm(M::VectorSpaceAtPoint, p, X) = norm(M.fiber.manifold, M.point, X)
@doc raw"""
project(B::VectorBundle, p)
Project the point `p` from the ambient space of the vector bundle `B`
over manifold `B.fiber` (denoted $\mathcal M$) to the vector bundle.
Notation:
* The point $p = (x_p, V_p)$ where $x_p$ belongs to the ambient space of $\mathcal M$
and $V_p$ belongs to the ambient space of the
fiber $F=π^{-1}(\{x_p\})$ of the vector bundle $B$ where $π$ is the
canonical projection of that vector bundle $B$.
The projection is calculated by projecting the point $x_p$ to the manifold $\mathcal M$
and then projecting the vector $V_p$ to the tangent space $T_{x_p}\mathcal M$.
"""
project(::VectorBundle, ::Any)
@doc raw"""
project(M::TangentSpaceAtPoint, p)
Project the point `p` from the tangent space `M`, that is project the vector `p`
tangent at `M.point`.
"""
project(::TangentSpaceAtPoint, ::Any)
function project!(B::VectorBundle, q, p)
px, pVx = submanifold_components(B.manifold, p)
qx, qVx = submanifold_components(B.manifold, q)
project!(B.manifold, qx, px)
project!(B.manifold, qVx, qx, pVx)
return q
end
function project!(M::TangentSpaceAtPoint, q, p)
return project!(M.fiber.manifold, q, M.point, p)
end
@doc raw"""
project(B::VectorBundle, p, X)
Project the element `X` of the ambient space of the tangent space $T_p B$
to the tangent space $T_p B$.
Notation:
* The point $p = (x_p, V_p)$ where $x_p ∈ \mathcal M$ and $V_p$ belongs to the
fiber $F=π^{-1}(\{x_p\})$ of the vector bundle $B$ where $π$ is the
canonical projection of that vector bundle $B$.
* The vector $x = (V_{X,M}, V_{X,F})$ where $x_p$ belongs to the ambient space of $T_{x_p}\mathcal M$
and $V_{X,F}$ belongs to the ambient space of the
fiber $F=π^{-1}(\{x_p\})$ of the vector bundle $B$ where $π$ is the
canonical projection of that vector bundle $B$.
The projection is calculated by projecting $V_{X,M}$ to tangent space $T_{x_p}\mathcal M$
and then projecting the vector $V_{X,F}$ to the fiber $F$.
"""
project(::VectorBundle, ::Any, ::Any)
@doc raw"""
project(M::TangentSpaceAtPoint, p, X)
Project the vector `X` from the tangent space `M`, that is project the vector `X`
tangent at `M.point`.
"""
project(::TangentSpaceAtPoint, ::Any, ::Any)
function project!(B::VectorBundle, Y, p, X)
px, Vx = submanifold_components(B.manifold, p)
VXM, VXF = submanifold_components(B.manifold, X)
VYM, VYF = submanifold_components(B.manifold, Y)
project!(B.manifold, VYM, px, VXM)
project!(B.manifold, VYF, px, VXF)
return Y
end
function project!(M::TangentSpaceAtPoint, Y, p, X)
return project!(M.fiber.manifold, Y, M.point, X)
end
"""
project(B::VectorBundleFibers, p, X)
Project vector `X` from the vector space of type `B.fiber` at point `p`.
"""
function project(B::VectorBundleFibers, p, X)
Y = allocate_result(B, project, p, X)
return project!(B, Y, p, X)
end
function project!(B::VectorBundleFibers{<:TangentSpaceType}, Y, p, X)
return project!(B.manifold, Y, p, X)
end
function project!(B::VectorBundleFibers, Y, p, X)
return error("project! not implemented for vector space family of type $(typeof(B)), output vector of type $(typeof(Y)) and input vector at point $(typeof(p)) with type of w $(typeof(X)).")
end
Base.@propagate_inbounds Base.setindex!(x::FVector, val, i) = setindex!(x.data, val, i)
"""
setindex!(p::ProductRepr, val, M::VectorBundle, s::Symbol)
p[M::VectorBundle, s] = val
Set the element(s) at index `s` of a point `p` on a [`VectorBundle`](@ref) `M` to `val` by
using the symbols `:point` and `:vector` for the base and vector component, respectively.
!!! note
The *content* of element of `p` is replaced, not the element itself.
"""
@inline function Base.setindex!(x::ProductRepr, val, M::VectorBundle, s::Symbol)
if s === :point
return copyto!(submanifold_component(M, x, Val(1)), val)
elseif s === :vector
return copyto!(submanifold_component(M, x, Val(2)), val)
else
throw(DomainError(s, "unknown component $s on $M."))
end
end
function representation_size(B::VectorBundleFibers{<:TCoTSpaceType})
return representation_size(B.manifold)
end
function representation_size(B::VectorBundle)
len_manifold = prod(representation_size(B.manifold))
len_vs = prod(representation_size(B.fiber))
return (len_manifold + len_vs,)
end
function representation_size(B::TangentSpaceAtPoint)
return representation_size(B.fiber.manifold)
end
@doc raw"""
sharp(M::Manifold, p, ξ::FVector)
Compute the sharp isomorphism (one of the musical isomorphisms) of vector `ξ`
from the vector space `M` at point `p` from the underlying [`Manifold`](@ref).
The function can be used for example to transform vectors
from the cotangent bundle to vectors from the tangent bundle
$♯ : T^{*}\mathcal M → T\mathcal M$
"""
function sharp(M::Manifold, p, ξ::FVector)
X = allocate_result(M, sharp, ξ, p)
return sharp!(M, X, p, ξ)
end
function sharp!(M::Manifold, X::FVector, p, ξ::FVector)
return error(
"sharp! not implemented for vector bundle fibers space " *
"of type $(typeof(M)), vector of type $(typeof(X)), point of " *
"type $(typeof(p)) and vector of type $(typeof(ξ)).",
)
end
@decorator_transparent_signature sharp!(
M::AbstractDecoratorManifold,
X::TFVector,
p,
ξ::CoTFVector,
)
Base.show(io::IO, ::TangentSpaceType) = print(io, "TangentSpace")
Base.show(io::IO, ::CotangentSpaceType) = print(io, "CotangentSpace")
function Base.show(io::IO, tpt::TensorProductType)
return print(io, "TensorProductType(", join(tpt.spaces, ", "), ")")
end
function Base.show(io::IO, fiber::VectorBundleFibers)
return print(io, "VectorBundleFibers($(fiber.fiber), $(fiber.manifold))")
end
function Base.show(io::IO, ::MIME"text/plain", vs::VectorSpaceAtPoint)
summary(io, vs)
println(io, "\nFiber:")
pre = " "
sf = sprint(show, "text/plain", vs.fiber; context = io, sizehint = 0)
sf = replace(sf, '\n' => "\n$(pre)")
println(io, pre, sf)
println(io, "Base point:")
sp = sprint(show, "text/plain", vs.point; context = io, sizehint = 0)
sp = replace(sp, '\n' => "\n$(pre)")
return print(io, pre, sp)
end
function Base.show(io::IO, ::MIME"text/plain", TpM::TangentSpaceAtPoint)
println(io, "Tangent space to the manifold $(base_manifold(TpM)) at point:")
pre = " "
sp = sprint(show, "text/plain", TpM.point; context = io, sizehint = 0)
sp = replace(sp, '\n' => "\n$(pre)")
return print(io, pre, sp)
end
Base.show(io::IO, vb::VectorBundle) = print(io, "VectorBundle($(vb.type), $(vb.manifold))")
Base.show(io::IO, vb::TangentBundle) = print(io, "TangentBundle($(vb.manifold))")
Base.show(io::IO, vb::CotangentBundle) = print(io, "CotangentBundle($(vb.manifold))")
allocate(x::FVector) = FVector(x.type, allocate(x.data))
allocate(x::FVector, ::Type{T}) where {T} = FVector(x.type, allocate(x.data, T))
"""
allocate_result(B::VectorBundleFibers, f, x...)
Allocates an array for the result of function `f` that is
an element of the vector space of type `B.fiber` on manifold `B.manifold`
and arguments `x...` for implementing the non-modifying operation
using the modifying operation.
"""
function allocate_result(B::VectorBundleFibers, f, x...)
T = allocate_result_type(B, f, x)
return allocate(x[1], T)
end
function allocate_result(M::Manifold, ::typeof(flat), w::TFVector, x)
return FVector(CotangentSpace, allocate(w.data))
end
function allocate_result(M::Manifold, ::typeof(sharp), w::CoTFVector, x)
return FVector(TangentSpace, allocate(w.data))
end
"""
allocate_result_type(B::VectorBundleFibers, f, args::NTuple{N,Any}) where N
Returns type of element of the array that will represent the result of
function `f` for representing an operation with result in the vector space `fiber`
for manifold `M` on given arguments (passed at a tuple).
"""
function allocate_result_type(::VectorBundleFibers, f, args::NTuple{N,Any}) where {N}
return typeof(mapreduce(eti -> one(number_eltype(eti)), +, args))
end
Base.size(x::FVector) = size(x.data)
function submanifold_component(M::Manifold, x::FVector, i::Val)
return submanifold_component(M, x.data, i)
end
submanifold_component(x::FVector, i::Val) = submanifold_component(x.data, i)
submanifold_components(M::Manifold, x::FVector) = submanifold_components(M, x.data)
submanifold_components(x::FVector) = submanifold_components(x.data)
"""
vector_bundle_transport(fiber::VectorSpaceType, M::Manifold)
Determine the vector tranport used for [`exp`](@ref exp(::VectorBundle, ::Any...)) and
[`log`](@ref log(::VectorBundle, ::Any...)) maps on a vector bundle with vector space type
`fiber` and manifold `M`.
"""
vector_bundle_transport(::VectorSpaceType, ::Manifold) = ParallelTransport()
"""
vector_space_dimension(B::VectorBundleFibers)
Dimension of the vector space of type `B`.
"""
function vector_space_dimension(B::VectorBundleFibers)
return error("vector_space_dimension not implemented for vector space family $(typeof(B)).")
end
function vector_space_dimension(B::VectorBundleFibers{<:TCoTSpaceType})
return manifold_dimension(B.manifold)
end
function vector_space_dimension(B::VectorBundleFibers{<:TensorProductType})
dim = 1
for space in B.fiber.spaces
dim *= vector_space_dimension(VectorBundleFibers(space, B.manifold))
end
return dim
end
function vector_transport_direction(M::VectorBundle, p, X, d)