Refactor derivative names (#276)

* Remove unused file

* Remove partialpartial

* Add `site_derivative`

* Fixup docstrings

* rename MPO derivative structs

* rename JordanMPO derivative structs

* update comment

* Rename projection operators

* rename `**_proj` functions

* Add ProjectionOperator tests

* Fix proper normalization for projectionoperator expval

* Remove `∂_` functions

* Remove unused `site_derivative`

* Consistently use `CartesianIndex`

* Condense a bunch of boilerplate

* Small fixes

* Fix typo

* formatter

Author: lkdvos

src/algorithms/ED.jl

@@ -72,7 +72,7 @@ function exact_diagonalization(H::FiniteMPOHamiltonian;
     # optimize the middle site
     # Because the MPS is full rank - this is equivalent to the full Hamiltonian
     AC₀ = state.AC[middle_site]
-    H_ac = ∂∂AC(middle_site, state, H, envs)
+    H_ac = AC_hamiltonian(middle_site, state, H, state, envs)
     vals, vecs, convhist = eigsolve(H_ac, AC₀, num, which, alg)
 
     # repack eigenstates

src/algorithms/approximate/fvomps.jl

@@ -8,7 +8,7 @@ function approximate!(ψ::AbstractFiniteMPS, Oϕ, alg::DMRG2,
         for iter in 1:(alg.maxiter)
             ϵ = 0.0
             for pos in [1:(length(ψ) - 1); (length(ψ) - 2):-1:1]
-                AC2′ = ac2_proj(pos, ψ, Oϕ, envs)
+                AC2′ = AC2_projection(pos, ψ, Oϕ, envs)
                 al, c, ar, = tsvd!(AC2′; trunc=alg.trscheme)
 
                 AC2 = ψ.AC[pos] * _transpose_tail(ψ.AR[pos + 1])
@@ -45,7 +45,7 @@ function approximate!(ψ::AbstractFiniteMPS, Oϕ, alg::DMRG, envs=environments(
         for iter in 1:(alg.maxiter)
             ϵ = 0.0
             for pos in [1:(length(ψ) - 1); length(ψ):-1:2]
-                AC′ = ac_proj(pos, ψ, Oϕ, envs)
+                AC′ = AC_projection(pos, ψ, Oϕ, envs)
                 AC = ψ.AC[pos]
                 ϵ = max(ϵ, norm(AC′ - AC) / norm(AC′))
 

src/algorithms/approximate/idmrg.jl

@@ -12,7 +12,8 @@ function approximate!(ψ::MultilineMPS, toapprox::Tuple{<:MultilineMPO,<:Multili
             # left to right sweep
             for col in 1:size(ψ, 2)
                 for row in 1:size(ψ, 1)
-                    ψ.AC[row + 1, col] = ac_proj(row, col, ψ, toapprox, envs)
+                    ψ.AC[row + 1, col] = AC_projection(CartesianIndex(row, col), ψ,
+                                                       toapprox, envs)
                     normalize!(ψ.AC[row + 1, col])
                     ψ.AL[row + 1, col], ψ.C[row + 1, col] = leftorth!(ψ.AC[row + 1, col])
                 end
@@ -22,7 +23,8 @@ function approximate!(ψ::MultilineMPS, toapprox::Tuple{<:MultilineMPO,<:Multili
             # right to left sweep
             for col in size(ψ, 2):-1:1
                 for row in 1:size(ψ, 1)
-                    ψ.AC[row + 1, col] = ac_proj(row, col, ψ, toapprox, envs)
+                    ψ.AC[row + 1, col] = AC_projection(CartesianIndex(row, col),
+                                                       ψ, toapprox, envs)
                     normalize!(ψ.AC[row + 1, col])
                     ψ.C[row + 1, col - 1], temp = rightorth!(_transpose_tail(ψ.AC[row + 1,
                                                                                   col]))
@@ -71,7 +73,7 @@ function approximate!(ψ::MultilineMPS, toapprox::Tuple{<:MultilineMPO,<:Multili
             # sweep from left to right
             for col in 1:size(ψ, 2)
                 for row in 1:size(ψ, 1)
-                    AC2′ = ac2_proj(row, col, ψ, toapprox, envs)
+                    AC2′ = AC2_projection(CartesianIndex(row, col), ψ, toapprox, envs)
                     al, c, ar, = tsvd!(AC2′; trunc=alg.trscheme, alg=alg.alg_svd)
                     normalize!(c)
 
@@ -88,9 +90,9 @@ function approximate!(ψ::MultilineMPS, toapprox::Tuple{<:MultilineMPO,<:Multili
             # sweep from right to left
             for col in (size(ψ, 2) - 1):-1:0
                 for row in 1:size(ψ, 1)
-                    # TODO: also write this as ac2_proj?
+                    # TODO: also write this as AC2_projection?
                     AC2 = ϕ.AL[row, col] * _transpose_tail(ϕ.AC[row, col + 1])
-                    AC2′ = ∂∂AC2(row, col, ψ, O, envs) * AC2
+                    AC2′ = AC2_hamiltonian(CartesianIndex(row, col), ψ, O, ϕ, envs) * AC2
                     al, c, ar, = tsvd!(AC2′; trunc=alg.trscheme, alg=alg.alg_svd)
                     normalize!(c)
 

src/algorithms/approximate/vomps.jl

@@ -55,8 +55,6 @@ function Base.iterate(it::IterativeSolver{<:VOMPS}, state::VOMPSState{<:Any,<:Tu
     return (mps, envs, ϵ), it.state
 end
 
-# TODO: ac_proj and c_proj should be rewritten to also be simply ∂AC/∂C functions
-# once these have better support for different above/below mps
 function localupdate_step!(::IterativeSolver{<:VOMPS}, state::VOMPSState{<:Any,<:Tuple},
                            ::SerialScheduler)
     alg_orth = QRpos()
@@ -65,9 +63,11 @@ function localupdate_step!(::IterativeSolver{<:VOMPS}, state::VOMPSState{<:Any,<
     dst_ACs = state.mps isa Multiline ? eachcol(ACs) : ACs
 
     foreach(eachsite) do site
-        AC = circshift([ac_proj(row, site, state.mps, state.operator, state.envs)
+        AC = circshift([AC_projection(CartesianIndex(row, site), state.mps, state.operator,
+                                      state.envs)
                         for row in 1:size(state.mps, 1)], 1)
-        C = circshift([c_proj(row, site, state.mps, state.operator, state.envs)
+        C = circshift([C_projection(CartesianIndex(row, site), state.mps, state.operator,
+                                    state.envs)
                        for row in 1:size(state.mps, 1)], 1)
         dst_ACs[site] = regauge!(AC, C; alg=alg_orth)
         return nothing
@@ -87,11 +87,13 @@ function localupdate_step!(::IterativeSolver{<:VOMPS}, state::VOMPSState{<:Any,<
         local AC, C
         @sync begin
             Threads.@spawn begin
-                AC = circshift([ac_proj(row, site, state.mps, state.operator, state.envs)
+                AC = circshift([AC_projection(CartesianIndex(row, site), state.mps,
+                                              state.operator, state.envs)
                                 for row in 1:size(state.mps, 1)], 1)
             end
             Threads.@spawn begin
-                C = circshift([c_proj(row, site, state.mps, state.operator, state.envs)
+                C = circshift([C_projection(CartesianIndex(row, site), state.mps,
+                                            state.operator, state.envs)
                                for row in 1:size(state.mps, 1)], 1)
             end
         end

src/algorithms/changebonds/optimalexpand.jl

@@ -25,7 +25,7 @@ function changebonds(ψ::InfiniteMPS, H::InfiniteMPOHamiltonian, alg::OptimalExp
     for i in 1:length(ψ)
         # determine optimal expansion spaces around bond i
         AC2 = _transpose_front(ψ.AC[i]) * _transpose_tail(ψ.AR[i + 1])
-        AC2 = ∂∂AC2(i, ψ, H, envs) * AC2
+        AC2 = AC2_hamiltonian(i, ψ, H, ψ, envs) * AC2
 
         # Use the nullspaces and SVD decomposition to determine the optimal expansion space
         VL = leftnull(ψ.AL[i])
@@ -51,7 +51,7 @@ function changebonds(ψ::MultilineMPS, H, alg::OptimalExpand, envs=environments(
     # determine optimal expansion spaces around bond i
     for i in 1:size(ψ, 1), j in 1:size(ψ, 2)
         AC2 = _transpose_front(ψ.AC[i - 1, j]) * _transpose_tail(ψ.AR[i - 1, j + 1])
-        AC2 = ∂∂AC2(i - 1, j, ψ, H, envs) * AC2
+        AC2 = AC2_hamiltonian(CartesianIndex(i - 1, j), ψ, H, ψ, envs) * AC2
 
         # Use the nullspaces and SVD decomposition to determine the optimal expansion space
         VL = leftnull(ψ.AL[i, j])
@@ -80,7 +80,7 @@ function changebonds!(ψ::AbstractFiniteMPS, H, alg::OptimalExpand, envs=environ
 
     for i in 1:(length(ψ) - 1)
         AC2 = _transpose_front(ψ.AC[i]) * _transpose_tail(ψ.AR[i + 1])
-        AC2 = ∂∂AC2(i, ψ, H, envs) * AC2
+        AC2 = AC2_hamiltonian(i, ψ, H, ψ, envs) * AC2
 
         #Calculate nullspaces for left and right
         NL = leftnull(ψ.AC[i])

src/algorithms/changebonds/vumpssvd.jl

@@ -52,11 +52,11 @@ function changebonds_n(state::InfiniteMPS, H, alg::VUMPSSvdCut, envs=environment
     for loc in 1:length(state)
         @plansor AC2[-1 -2; -3 -4] := state.AC[loc][-1 -2; 1] * state.AR[loc + 1][1 -4; -3]
 
-        h_ac2 = ∂∂AC2(loc, state, H, envs)
-        _, nAC2 = fixedpoint(h_ac2, AC2, :SR, alg.alg_eigsolve)
+        Hac2 = AC2_hamiltonian(loc, state, H, state, envs)
+        _, nAC2 = fixedpoint(Hac2, AC2, :SR, alg.alg_eigsolve)
 
-        h_c = ∂∂C(loc + 1, state, H, envs)
-        _, nC2 = fixedpoint(h_c, state.C[loc + 1], :SR, alg.alg_eigsolve)
+        Hc = C_hamiltonian(loc + 1, state, H, state, envs)
+        _, nC2 = fixedpoint(Hc, state.C[loc + 1], :SR, alg.alg_eigsolve)
 
         #svd ac2, get new AL1 and S,V ---> AC
         AL1, S, V, eps = tsvd!(nAC2; trunc=alg.trscheme, alg=alg.alg_svd)