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Refactor mixed_canonize! #14

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Feb 22, 2024
Merged

Refactor mixed_canonize! #14

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758b6b1
Rename `mode` kwarg to `method`
mofeing Feb 21, 2024
deebc3d
Refactor `mixed_canonize!`
mofeing Feb 21, 2024
754ca92
Move `isleftcanonical`,`isrightcanonical` to source
mofeing Feb 22, 2024
9a20417
Refactor `canonize_site!`
mofeing Feb 22, 2024
c764361
Fix `canonize_site!`
mofeing Feb 22, 2024
11e5aad
Refactor `isleftcanonical`,`isrightcanonical`
mofeing Feb 22, 2024
cf0ac4c
Export `truncate!`, `isleftcanonical`, `isrightcanonical`
mofeing Feb 22, 2024
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78 changes: 52 additions & 26 deletions src/Ansatz/Chain.jl
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Expand Up @@ -147,24 +147,24 @@ end
canonize_site(tn::Chain, args...; kwargs...) = canonize_site!(deepcopy(tn), args...; kwargs...)
canonize_site!(tn::Chain, args...; kwargs...) = canonize_site!(boundary(tn), tn, args...; kwargs...)

# NOTE: in mode == :svd the spectral weights are stored in a vector connected to the now virtual hyperindex!
function canonize_site!(::Open, tn::Chain, site::Site; direction::Symbol, mode = :qr)
# NOTE: in method == :svd the spectral weights are stored in a vector connected to the now virtual hyperindex!
function canonize_site!(::Open, tn::Chain, site::Site; direction::Symbol, method = :qr)
left_inds = Symbol[]
right_inds = Symbol[]

virtualind = if direction === :left
site == Site(nsites(tn)) && throw(ArgumentError("Cannot left-canonize right-most tensor"))
push!(right_inds, rightindex(tn, site))
site == Site(1) && throw(ArgumentError("Cannot right-canonize left-most tensor"))
push!(right_inds, leftindex(tn, site))

site == Site(1) || push!(left_inds, leftindex(tn, site))
site == Site(nsites(tn)) || push!(left_inds, rightindex(tn, site))
push!(left_inds, Quantum(tn)[site])

only(right_inds)
elseif direction === :right
site == Site(1) && throw(ArgumentError("Cannot right-canonize left-most tensor"))
push!(right_inds, leftindex(tn, site))
site == Site(nsites(tn)) && throw(ArgumentError("Cannot left-canonize right-most tensor"))
push!(right_inds, rightindex(tn, site))

site == Site(nsites(tn)) || push!(left_inds, rightindex(tn, site))
site == Site(1) || push!(left_inds, leftindex(tn, site))
push!(left_inds, Quantum(tn)[site])

only(right_inds)
Expand All @@ -173,12 +173,12 @@ function canonize_site!(::Open, tn::Chain, site::Site; direction::Symbol, mode =
end

tmpind = gensym(:tmp)
if mode == :qr
qr!(TensorNetwork(tn); left_inds, right_inds, virtualind = tmpind)
elseif mode == :svd
if method === :svd
svd!(TensorNetwork(tn); left_inds, right_inds, virtualind = tmpind)
elseif method === :qr
qr!(TensorNetwork(tn); left_inds, right_inds, virtualind = tmpind)
else
throw(ArgumentError("Unknown mode=:$mode"))
throw(ArgumentError("Unknown factorization method=:$method"))
end

contract!(TensorNetwork(tn), virtualind)
Expand All @@ -187,6 +187,40 @@ function canonize_site!(::Open, tn::Chain, site::Site; direction::Symbol, mode =
return tn
end

function isleftcanonical(qtn::Chain, site; atol::Real = 1e-12)
right_ind = rightindex(qtn, site)

# we are at right-most site, which cannot be left-canonical
if isnothing(right_ind)
return false
end

# TODO is replace(conj(A)...) copying too much?
tensor = select(qtn, :tensor, site)
contracted = contract(tensor, replace(conj(tensor), right_ind => :new_ind_name))
n = size(tensor, right_ind)
identity_matrix = Matrix(I, n, n)

return isapprox(contracted, identity_matrix; atol)
end

function isrightcanonical(qtn::Chain, site; atol::Real = 1e-12)
left_ind = leftindex(qtn, site)

# we are at left-most site, which cannot be right-canonical
if isnothing(left_ind)
return false
end

#TODO is replace(conj(A)...) copying too much?
tensor = select(qtn, :tensor, site)
contracted = contract(tensor, replace(conj(tensor), left_ind => :new_ind_name))
n = size(tensor, left_ind)
identity_matrix = Matrix(I, n, n)

return isapprox(contracted, identity_matrix; atol)
end

mixed_canonize(tn::Chain, args...; kwargs...) = mixed_canonize!(deepcopy(tn), args...; kwargs...)
mixed_canonize!(tn::Chain, args...; kwargs...) = mixed_canonize!(boundary(tn), tn, args...; kwargs...)

Expand All @@ -198,22 +232,14 @@ for i < center the tensors are left-canonical and for i > center the tensors are
and in the center there is a matrix with singular values.
"""
function mixed_canonize!(::Open, tn::Chain, center::Site) # TODO: center could be a range of sites
N = length(sites(tn))

# Left-to-right QR sweep -> get left-canonical tensors
for i in 1:N-1
canonize_site!(tn, Site(i); direction = :left, mode = :qr)
# left-to-right QR sweep (left-canonical tensors)
for i in 1:center.id-1
canonize_site!(tn, Site(i); direction = :right, method = :qr)
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end

# Right-to-left QR sweep -> get right-canonical tensors for i > center
for i in N:-1:1
if i > center.id
canonize_site!(tn, Site(i); direction = :right, mode = :qr)
elseif i == center.id
canonize_site!(tn, Site(i); direction = :left, mode = :svd)
else
canonize_site!(tn, Site(i); direction = :left, mode = :qr)
end
# right-to-left QR sweep (right-canonical tensors)
for i in nsites(tn):-1:center.id+1
canonize_site!(tn, Site(i); direction = :left, method = :qr)
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end

return tn
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4 changes: 2 additions & 2 deletions src/Qrochet.jl
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Expand Up @@ -17,8 +17,8 @@ export Product
include("Ansatz/Chain.jl")
export Chain
export MPS, pMPS, MPO, pMPO
export leftindex, rightindex, canonize_site, canonize_site!
export mixed_canonize, mixed_canonize!
export leftindex, rightindex, canonize_site, canonize_site!, truncate!
export mixed_canonize, mixed_canonize!, isleftcanonical, isrightcanonical

# reexports from Tenet
using Tenet
Expand Down
88 changes: 37 additions & 51 deletions test/Ansatz/Chain_test.jl
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Expand Up @@ -54,69 +54,55 @@
@testset "Canonization" begin
using Tenet

function is_left_canonical(qtn, s::Site)
label_r = rightindex(qtn, s)
A = select(qtn, :tensor, s)
try
contracted = contract(A, replace(conj(A), label_r => :new_ind_name))
return isapprox(contracted, Matrix{Float64}(I, size(A, label_r), size(A, label_r)), atol = 1e-12)
catch
return false
end
end

function is_right_canonical(qtn, s::Site)
label_l = leftindex(qtn, s)
A = select(qtn, :tensor, s)
try
contracted = contract(A, replace(conj(A), label_l => :new_ind_name))
return isapprox(contracted, Matrix{Float64}(I, size(A, label_l), size(A, label_l)), atol = 1e-12)
catch
return false
end
end

@testset "canonize_site" begin
qtn = Chain(State(), Open(), [rand(4, 4), rand(4, 4, 4), rand(4, 4)])

@test_throws ArgumentError canonize_site!(qtn, Site(1); direction = :right)
@test_throws ArgumentError canonize_site!(qtn, Site(3); direction = :left)

for mode in [:qr, :svd]
for i in 1:length(sites(qtn))
if i != 1
canonized = canonize_site(qtn, Site(i); direction = :right, mode = mode)
@test is_right_canonical(canonized, Site(i))
@test isapprox(
contract(transform(TensorNetwork(canonized), Tenet.HyperindConverter())),
contract(TensorNetwork(qtn)),
)
elseif i != length(sites(qtn))
canonized = canonize_site(qtn, Site(i); direction = :left, mode = mode)
@test is_left_canonical(canonized, Site(i))
@test isapprox(
contract(transform(TensorNetwork(canonized), Tenet.HyperindConverter())),
contract(TensorNetwork(qtn)),
)
end
end
@test_throws ArgumentError canonize_site!(qtn, Site(1); direction = :left)
@test_throws ArgumentError canonize_site!(qtn, Site(3); direction = :right)

for method in [:qr, :svd]
canonized = canonize_site(qtn, site"1"; direction = :right, method = method)
@test isleftcanonical(canonized, site"1")
@test isapprox(
contract(transform(TensorNetwork(canonized), Tenet.HyperindConverter())),
contract(TensorNetwork(qtn)),
)

canonized = canonize_site(qtn, site"2"; direction = :right, method = method)
@test isleftcanonical(canonized, site"2")
@test isapprox(
contract(transform(TensorNetwork(canonized), Tenet.HyperindConverter())),
contract(TensorNetwork(qtn)),
)

canonized = canonize_site(qtn, site"2"; direction = :left, method = method)
@test isrightcanonical(canonized, site"2")
@test isapprox(
contract(transform(TensorNetwork(canonized), Tenet.HyperindConverter())),
contract(TensorNetwork(qtn)),
)

canonized = canonize_site(qtn, site"3"; direction = :left, method = method)
@test isrightcanonical(canonized, site"3")
@test isapprox(
contract(transform(TensorNetwork(canonized), Tenet.HyperindConverter())),
contract(TensorNetwork(qtn)),
)
end

# Ensure that svd creates a new tensor
@test length(tensors(canonize_site(qtn, Site(2); direction = :right, mode = :svd))) == 4
@test length(tensors(canonize_site(qtn, Site(2); direction = :left, method = :svd))) == 4
end

@testset "mixed_canonize" begin
qtn = Chain(State(), Open(), [rand(4, 4), rand(4, 4, 4), rand(4, 4, 4), rand(4, 4, 4), rand(4, 4)])
canonized = mixed_canonize(qtn, Site(3))

@test is_left_canonical(canonized, Site(1))
@test is_left_canonical(canonized, Site(2))
@test is_left_canonical(canonized, Site(3))
@test is_right_canonical(canonized, Site(4))
@test is_right_canonical(canonized, Site(5))

@test length(tensors(canonized)) == 6 # 5 tensors + 1 singular value matrix
@test isleftcanonical(canonized, Site(1))
@test isleftcanonical(canonized, Site(2))
@test !isleftcanonical(canonized, Site(3)) && !isrightcanonical(canonized, Site(3))
@test isrightcanonical(canonized, Site(4))
@test isrightcanonical(canonized, Site(5))

@test isapprox(
contract(transform(TensorNetwork(canonized), Tenet.HyperindConverter())),
Expand Down
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