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Changes to work with ITensorMPOConstruction #1

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2a953b4
Changes to work with ITensorMPOConstruction
corbett5 Feb 23, 2024
dc1083f
Switched to constructing an OpIDSum.
corbett5 Feb 25, 2024
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51 changes: 38 additions & 13 deletions gen_mpo_min_julia.jl
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@@ -1,6 +1,28 @@
using LinearAlgebra
using WignerSymbols
using ITensors
using ITensorMPOConstruction


↓ = false
↑ = true

function create_op_cache_vec(sites::Vector{<:Index})::OpCacheVec
## The identity must be the first operator.
## The next six operators are the only ones that are used directly in MPO construction.
operatorNames = ["I", "Cdn", "Cup", "Cdagdn", "Cdagup", "Ndn", "Nup",
"Cup * Cdn", "Cup * Cdagdn", "Cup * Ndn",
"Cdagup * Cdn", "Cdagup * Cdagdn", "Cdagup * Ndn",
"Nup * Cdn", "Nup * Cdagdn", "Nup * Ndn"]

return [[OpInfo(ITensors.Op(name, n), sites[n]) for name in operatorNames] for n in eachindex(sites)]
end

opC(j::CartesianIndex, spin::Bool, mapping::Array{Int}) = OpID(2 + spin, mapping[wrap_around(size(mapping), j)])
opC(j::Int, spin::Bool) = OpID(2 + spin, j)

opCdag(j::CartesianIndex, spin::Bool, mapping::Array{Int}) = OpID(4 + spin, mapping[wrap_around(size(mapping), j)])
opCdag(j::Int, spin::Bool) = OpID(4 + spin, j)

function calc_int_ps(nm, ps_pot :: Vector{Float64})
## N = 2s+1, get V[i,j,k,l]
Expand Down Expand Up @@ -67,8 +89,8 @@ end

function generate_hmt_fuzzy_ising_4(nm :: Int ;
ps_pot_u = [4.75, 1.0], fld_h = 3.16)
os = OpSum()
int_el = calc_int_ps(nm, ps_pot_u)
os = OpIDSum{Float64}()
@time "calc_int_ps" int_el = calc_int_ps(nm, ps_pot_u)
for m1 in 1 : nm
for m2 in 1 : nm
for m3 in 1 : nm
Expand All @@ -77,26 +99,29 @@ function generate_hmt_fuzzy_ising_4(nm :: Int ;
continue
end
V = int_el[m1, m2, m3]
os += V * 2, "Cdagup", m1, "Cup", m4, "Cdagdn", m2, "Cdn", m3

push!(os, V * 2, opCdag(m1, ↑), opC(m4, ↑), opCdag(m2, ↓), opC(m3, ↓))
end
end
end
for m1 in 1 : nm
os += -2 * fld_h, "Sx", m1
push!(os, -fld_h, opCdag(m1, ↑), opC(m1, ↓))
push!(os, -fld_h, opCdag(m1, ↓), opC(m1, ↓))
end
return os
end

nm = 24
sites = [siteind("Electron", lz = m, conserve_sz = false, conserve_nf = true, conserve_lz = true, conserve_spin_parity = false) for m :: Int in 1 : nm]

opCacheVec = create_op_cache_vec(sites)
os = generate_hmt_fuzzy_ising_4(nm)
t0 = time()
hmt = MPO(os, sites ; cutoff = 1E-13)
t1 = time() - t0
@show t1
t0 = time()
hmt1 = MPO(os, sites ; cutoff = 1E-13)
t1 = time() - t0
@show t1
hmt = MPO_new(os, sites, opCacheVec; basisOpCacheVec=opCacheVec, tol=4e-8)

nm = 100
sites = [siteind("Electron", lz = m, conserve_sz = false, conserve_nf = true, conserve_lz = true, conserve_spin_parity = false) for m :: Int in 1 : nm]
opCacheVec = create_op_cache_vec(sites)
println("nm = $nm")
@time "Constructing opsum" os = generate_hmt_fuzzy_ising_4(nm)
@time "constructing MPO" hmt = MPO_new(os, sites, opCacheVec; basisOpCacheVec=opCacheVec, tol=4e-8)

@show maxlinkdim(hmt)