Trim direct ITensorMPS imports from tests, quarantine MPO cross-check (#332)

mtfishman · claude · web-flow · commit 31bb35429d22 · 2026-04-24T23:20:09.000Z
## Summary

Pull the remaining direct `ITensorMPS` imports out of the test files
that can trivially live without them, and quarantine the ones that
genuinely need the `ITensorMPS.MPO` construction as a reference oracle.

**Test changes:**
- `test/solvers/test_applyexp.jl`, `test/solvers/test_eigsolve.jl`:
switch `using ITensorMPS: OpSum` → `using ITensors.Ops: OpSum`. `OpSum`
lives in `ITensors.Ops`; `ITensorMPS` just re-exports it, so there was
no reason for these tests to depend on ITensorMPS for it.
- `test/test_opsum_to_ttn.jl`: trim to keep only the "Multiple onsite
terms" regression test — the one testset that does not need
`ITensorMPS.MPO(os, sites)` as a reference. Drop the `using ITensorMPS:
ITensorMPS` line.
- `test/test_opsum_to_ttn_mpo_cross_check.jl` (new): houses the four
testsets that compare `ttn(H, is)` against `prod(ITensorMPS.MPO(H,
sites))` — "OpSum to TTN", "OpSum to TTN QN", "OpSum to TTN Fermions",
"OpSum to TTN QN missing". These are verbatim from the old file (plus
their `to_matrix` helper). Quarantining them into a single file makes
the remaining ITensorMPS test-time dependency easy to track and delete
once there are internal equivalents for those correctness checks.

**No `src/` changes.** `ITensorMPS` was never a dependency of the
package itself (only of `test/`); this PR just reduces the test-time
surface that pulls it in.

**Version**

Patch-bump to `0.18.1` (test-only diff, substantive per the standard
`VersionCheck` classification).

Co-authored-by: Claude Opus 4.7 (1M context) &lt;noreply@anthropic.com&gt;
diff --git a/Project.toml b/Project.toml
@@ -1,6 +1,6 @@
 name = "ITensorNetworks"
 uuid = "2919e153-833c-4bdc-8836-1ea460a35fc7"
-version = "0.18.0"
+version = "0.18.1"
 authors = ["Matthew Fishman <mfishman@flatironinstitute.org>, Joseph Tindall <jtindall@flatironinstitute.org> and contributors"]
 
 [workspace]
diff --git a/test/solvers/test_applyexp.jl b/test/solvers/test_applyexp.jl
@@ -1,8 +1,8 @@
 using Graphs: add_edge!, add_vertex!, vertices
-using ITensorMPS: OpSum
 using ITensorNetworks:
     ITensorNetworks, applyexp, dmrg, maxlinkdim, siteinds, time_evolve, ttn
 using ITensors
+using ITensors.Ops: OpSum
 using NamedGraphs.NamedGraphGenerators: named_path_graph
 using NamedGraphs: NamedGraph
 using TensorOperations: TensorOperations
diff --git a/test/solvers/test_eigsolve.jl b/test/solvers/test_eigsolve.jl
@@ -1,7 +1,7 @@
 using Graphs: dst, edges, src, vertices
-using ITensorMPS: OpSum
 using ITensorNetworks: SweepIterator, dmrg, siteinds, ttn
 using ITensors
+using ITensors.Ops: OpSum
 using Suppressor: @capture_out
 using TensorOperations: TensorOperations
 using Test: @test, @testset
diff --git a/test/test_opsum_to_ttn.jl b/test/test_opsum_to_ttn.jl
@@ -1,81 +1,11 @@
 @eval module $(gensym())
-using DataGraphs: vertex_data
-using Dictionaries: Dictionary, getindices
-using Graphs: add_edge!, add_vertex!, rem_edge!, rem_vertex!, vertices
-using ITensorMPS: ITensorMPS
-using ITensorNetworks.ITensorsExtensions: replace_vertices
-using ITensorNetworks.ModelHamiltonians: ModelHamiltonians
+using Graphs: vertices
 using ITensorNetworks: ITensorNetworks, OpSum, siteinds, ttn
-using ITensors.NDTensors: matrix
-using ITensors: ITensors, @disable_warn_order, ITensor, Index, combinedind, combiner,
-    contract, dag, inds, removeqns
-using KrylovKit: eigsolve
-using LinearAlgebra: eigvals, norm
-using NamedGraphs.GraphsExtensions: leaf_vertices, post_order_dfs_vertices
-using NamedGraphs.NamedGraphGenerators: named_comb_tree, named_grid
-using Test: @test, @test_broken, @testset
-
-function to_matrix(t::ITensor)
-    c = combiner(inds(t; plev = 0))
-    tc = (t * c) * dag(c')
-    cind = combinedind(c)
-    return matrix(tc, cind', cind)
-end
+using ITensors: ITensors
+using NamedGraphs.NamedGraphGenerators: named_grid
+using Test: @test, @testset
 
 @testset "OpSum to TTN converter" begin
-    @testset "OpSum to TTN" begin
-        # small comb tree
-        auto_fermion_enabled = ITensors.using_auto_fermion()
-        tooth_lengths = fill(2, 3)
-        c = named_comb_tree(tooth_lengths)
-
-        is = siteinds("S=1/2", c)
-
-        # linearized version
-        linear_order = [4, 1, 2, 5, 3, 6]
-        vmap = Dictionary(collect(vertices(is))[linear_order], eachindex(linear_order))
-        sites = only.(collect(vertex_data(is)))[linear_order]
-
-        # test with next-to-nearest-neighbor Ising Hamiltonian
-        J1 = -1
-        J2 = 2
-        h = 0.5
-        H = ModelHamiltonians.ising(c; J1 = J1, J2 = J2, h = h)
-        # add combination of longer range interactions
-        Hlr = copy(H)
-        Hlr += 5, "Z", (1, 2), "Z", (2, 2), "Z", (3, 2)
-        Hlr += -4, "Z", (1, 1), "Z", (2, 2), "Z", (3, 1)
-        Hlr += 2.0, "Z", (2, 2), "Z", (3, 2)
-        Hlr += -1.0, "Z", (1, 2), "Z", (3, 1)
-
-        # root_vertex = (1, 2)
-        # println(leaf_vertices(is))
-
-        @testset "Svd approach" for root_vertex in leaf_vertices(is)
-            # get TTN Hamiltonian directly
-            Hsvd = ttn(H, is; root_vertex, cutoff = 1.0e-10)
-            # get corresponding MPO Hamiltonian
-            Hline = ITensorMPS.MPO(replace_vertices(v -> vmap[v], H), sites)
-            # compare resulting dense Hamiltonians
-            @disable_warn_order begin
-                Tttno = prod(Hline)
-                Tmpo = contract(Hsvd)
-            end
-            @test Tttno ≈ Tmpo rtol = 1.0e-6
-
-            Hsvd_lr = ttn(Hlr, is; root_vertex, cutoff = 1.0e-10)
-            Hline_lr = ITensorMPS.MPO(replace_vertices(v -> vmap[v], Hlr), sites)
-            @disable_warn_order begin
-                Tttno_lr = prod(Hline_lr)
-                Tmpo_lr = contract(Hsvd_lr)
-            end
-            @test Tttno_lr ≈ Tmpo_lr rtol = 1.0e-6
-        end
-        if auto_fermion_enabled
-            ITensors.enable_auto_fermion()
-        end
-    end
-
     @testset "Multiple onsite terms (regression test for issue #62)" begin
         auto_fermion_enabled = ITensors.using_auto_fermion()
         if !auto_fermion_enabled
@@ -98,169 +28,5 @@ end
             ITensors.enable_auto_fermion()
         end
     end
-
-    @testset "OpSum to TTN QN" begin
-        # small comb tree
-        tooth_lengths = fill(2, 3)
-        c = named_comb_tree(tooth_lengths)
-        is = siteinds("S=1/2", c; conserve_qns = true)
-        is_noqns = copy(is)
-        for v in vertices(is)
-            is_noqns[v] = removeqns(is_noqns[v])
-        end
-
-        # linearized version
-        linear_order = [4, 1, 2, 5, 3, 6]
-        vmap = Dictionary(collect(vertices(is))[linear_order], eachindex(linear_order))
-        sites = only.(collect(vertex_data(is)))[linear_order]
-
-        # test with next-to-nearest-neighbor Ising Hamiltonian
-        J1 = -1
-        J2 = 2
-        h = 0.5
-        H = ModelHamiltonians.heisenberg(c; J1 = J1, J2 = J2, h = h)
-        # add combination of longer range interactions
-        Hlr = copy(H)
-        Hlr += 5, "Z", (1, 2), "Z", (2, 2) #, "Z", (3,2)
-        Hlr += -4, "Z", (1, 1), "Z", (2, 2)
-        Hlr += 2.0, "Z", (2, 2), "Z", (3, 2)
-        Hlr += -1.0, "Z", (1, 2), "Z", (3, 1)
-
-        # root_vertex = (1, 2)
-        # println(leaf_vertices(is))
-
-        @testset "Svd approach" for root_vertex in leaf_vertices(is)
-            # get TTN Hamiltonian directly
-            Hsvd = ttn(H, is; root_vertex, cutoff = 1.0e-10)
-            # get corresponding MPO Hamiltonian
-            Hline = ITensorMPS.MPO(replace_vertices(v -> vmap[v], H), sites)
-            # compare resulting sparse Hamiltonians
-
-            @disable_warn_order begin
-                Tmpo = prod(Hline)
-                Tttno = contract(Hsvd)
-            end
-            @test Tttno ≈ Tmpo rtol = 1.0e-6
-
-            Hsvd_lr = ttn(Hlr, is; root_vertex, cutoff = 1.0e-10)
-            Hline_lr = ITensorMPS.MPO(replace_vertices(v -> vmap[v], Hlr), sites)
-            @disable_warn_order begin
-                Tttno_lr = prod(Hline_lr)
-                Tmpo_lr = contract(Hsvd_lr)
-            end
-            @test Tttno_lr ≈ Tmpo_lr rtol = 1.0e-6
-        end
-    end
-
-    @testset "OpSum to TTN Fermions" begin
-        # small comb tree
-        auto_fermion_enabled = ITensors.using_auto_fermion()
-        if !auto_fermion_enabled
-            ITensors.enable_auto_fermion()
-        end
-        tooth_lengths = fill(2, 3)
-        c = named_comb_tree(tooth_lengths)
-        is = siteinds("Fermion", c; conserve_nf = true)
-
-        # test with next-nearest neighbor tight-binding model
-        t = 1.0
-        tp = 0.4
-        U = 0.0
-        h = 0.5
-        H = ModelHamiltonians.tight_binding(c; t, tp, h)
-
-        # add combination of longer range interactions
-        Hlr = copy(H)
-
-        @testset "Svd approach" for root_vertex in leaf_vertices(is)
-            # get TTN Hamiltonian directly
-            Hsvd = ttn(H, is; root_vertex, cutoff = 1.0e-10)
-            # get corresponding MPO Hamiltonian
-            sites = [only(is[v]) for v in reverse(post_order_dfs_vertices(c, root_vertex))]
-            vmap = Dictionary(
-                reverse(post_order_dfs_vertices(c, root_vertex)),
-                1:length(sites)
-            )
-            Hline = ITensorMPS.MPO(replace_vertices(v -> vmap[v], H), sites)
-            @disable_warn_order begin
-                Tmpo = prod(Hline)
-                Tttno = contract(Hsvd)
-            end
-
-            # verify that the norm isn't 0 and thus the same (which would indicate a problem with the autofermion system
-            @test norm(Tmpo) > 0
-            @test norm(Tttno) > 0
-            @test norm(Tmpo) ≈ norm(Tttno) rtol = 1.0e-6
-
-            # TODO: fix comparison for fermionic tensors
-            @test_broken Tmpo ≈ Tttno
-            # In the meantime: matricize tensors and convert to dense Matrix to compare element by element
-            dTmm = to_matrix(Tmpo)
-            dTtm = to_matrix(Tttno)
-            @test any(>(1.0e-14), dTmm - dTtm)
-        end
-        if !auto_fermion_enabled
-            ITensors.disable_auto_fermion()
-        end
-    end
-
-    @testset "OpSum to TTN QN missing" begin
-        # small comb tree
-        tooth_lengths = fill(2, 3)
-        c = named_comb_tree(tooth_lengths)
-        c2 = copy(c)
-        ## add an internal vertex into the comb graph c2
-        add_vertex!(c2, (-1, 1))
-        add_edge!(c2, (-1, 1) => (2, 2))
-        add_edge!(c2, (-1, 1) => (3, 1))
-        add_edge!(c2, (-1, 1) => (2, 1))
-        rem_edge!(c2, (2, 1) => (2, 2))
-        rem_edge!(c2, (2, 1) => (3, 1))
-
-        is = siteinds("S=1/2", c; conserve_qns = true)
-        is_missing_site = siteinds("S=1/2", c2; conserve_qns = true)
-        is_missing_site[(-1, 1)] = Vector{Index}[]
-
-        # linearized version
-        linear_order = [4, 1, 2, 5, 3, 6]
-        vmap = Dictionary(collect(vertices(is))[linear_order], eachindex(linear_order))
-        sites =
-            only.(filter(d -> !isempty(d), collect(vertex_data(is_missing_site))))[linear_order]
-
-        J1 = -1
-        J2 = 2
-        h = 0.5
-        # connectivity of the Hamiltonian is that of the original comb graph
-        H = ModelHamiltonians.heisenberg(c; J1, J2, h)
-
-        # add combination of longer range interactions
-        Hlr = copy(H)
-        Hlr += 5, "Z", (1, 2), "Z", (2, 2)
-        Hlr += -4, "Z", (1, 1), "Z", (2, 2)
-        Hlr += 2.0, "Z", (2, 2), "Z", (3, 2)
-        Hlr += -1.0, "Z", (1, 2), "Z", (3, 1)
-
-        @testset "Svd approach" for root_vertex in leaf_vertices(is)
-            # get TTN Hamiltonian directly
-            Hsvd = ttn(H, is_missing_site; root_vertex, cutoff = 1.0e-10)
-            # get corresponding MPO Hamiltonian
-            Hline = ITensorMPS.MPO(replace_vertices(v -> vmap[v], H), sites)
-
-            # compare resulting sparse Hamiltonians
-            @disable_warn_order begin
-                Tmpo = prod(Hline)
-                Tttno = contract(Hsvd)
-            end
-            @test Tttno ≈ Tmpo rtol = 1.0e-6
-
-            Hsvd_lr = ttn(Hlr, is_missing_site; root_vertex, cutoff = 1.0e-10)
-            Hline_lr = ITensorMPS.MPO(replace_vertices(v -> vmap[v], Hlr), sites)
-            @disable_warn_order begin
-                Tttno_lr = prod(Hline_lr)
-                Tmpo_lr = contract(Hsvd_lr)
-            end
-            @test Tttno_lr ≈ Tmpo_lr rtol = 1.0e-6
-        end
-    end
 end
 end
diff --git a/test/test_opsum_to_ttn_mpo_cross_check.jl b/test/test_opsum_to_ttn_mpo_cross_check.jl
