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allow specifying index type for CachedExtensionHomomorphism #65

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Nov 15, 2023
Merged

allow specifying index type for CachedExtensionHomomorphism #65

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02fad62
allow specifying index type for CachedExtensionHomomorphism
kalmarek Nov 13, 2023
01f4f03
derive _int_type of ActionHomomorphisms from action (which is easily …
kalmarek Nov 14, 2023
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33 changes: 26 additions & 7 deletions src/ext_homomorphisms.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -17,11 +17,14 @@ PermutationGroups.degree(hom::InducedActionHomomorphism) = length(basis(hom))

coeff_type(hom::InducedActionHomomorphism) = coeff_type(action(hom))
_int_type(::Type{<:StarAlgebras.AbstractBasis{T,I}}) where {T,I} = I
_int_type(hom::InducedActionHomomorphism) = _int_type(typeof(basis(hom)))
_int_type(basis::StarAlgebras.AbstractBasis) = _int_type(typeof(basis))
_int_type(hom::InducedActionHomomorphism) = _int_type(basis(hom))

# Exceeding typemax(UInt32) here would mean e.g. that you're trying to block-diagonalize
# an SDP constraint of size 4_294_967_295 × 4_294_967_295, which is highly unlikely ;)
_int_type(::Type{<:Action}) = UInt32
_int_type(ac::Action) = _int_type(typeof(ac))

# Exceeding typemax(UInt16) here would mean e.g. that you're trying to block-diagonalize
# an SDP constraint of size 65535×65535, which is highly unlikely ;)
_int_type(::Type{<:InducedActionHomomorphism}) = UInt16

function induce(hom::InducedActionHomomorphism, g::GroupElement)
return induce(action(hom), hom, g)
Expand All @@ -43,7 +46,7 @@ end

function ExtensionHomomorphism(action::Action, basis)
return ExtensionHomomorphism(
_int_type(ExtensionHomomorphism),
_int_type(action),
action,
basis,
)
Expand Down Expand Up @@ -78,12 +81,13 @@ StarAlgebras.basis(h::CachedExtensionHomomorphism) = basis(h.ehom)
action(h::CachedExtensionHomomorphism) = action(h.ehom)

function CachedExtensionHomomorphism(
::Type{I},
G::Group,
action::Action,
basis;
precompute = false,
)
hom = ExtensionHomomorphism(action, basis)
) where {I}
hom = ExtensionHomomorphism(I, action, basis)
S = typeof(induce(hom, one(G)))
chom = CachedExtensionHomomorphism{eltype(G),S}(hom)
@sync if precompute
Expand All @@ -96,6 +100,21 @@ function CachedExtensionHomomorphism(
return chom
end

function CachedExtensionHomomorphism(
G::Group,
action::Action,
basis;
precompute = false,
)
return CachedExtensionHomomorphism(
_int_type(action),
G,
action,
basis;
precompute = precompute,
)
end

function induce(ac::Action, chom::CachedExtensionHomomorphism, g::GroupElement)
return _induce(ac, chom, g)
end
Expand Down
11 changes: 11 additions & 0 deletions test/action_permutation.jl
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Expand Up @@ -52,12 +52,23 @@ end
action = OnLetters()
tbl = SymbolicWedderburn.CharacterTable(Rational{Int}, G)
ehom = SymbolicWedderburn.CachedExtensionHomomorphism(
Int32,
G,
action,
words;
precompute = true,
)
@test all(g ∈ keys(ehom.cache) for g in G) # we actually cached
@test typeof(SymbolicWedderburn.induce(ehom, one(G))) == Perm{Int32}

ehom = SymbolicWedderburn.CachedExtensionHomomorphism(
G,
action,
words;
precompute = true,
)
@test all(g ∈ keys(ehom.cache) for g in G) # we actually cached
@test typeof(SymbolicWedderburn.induce(ehom, one(G))) == Perm{UInt32} # the default

ψ = SymbolicWedderburn.action_character(ehom, tbl)
@test SymbolicWedderburn.constituents(ψ) == [40, 22, 18]
Expand Down
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