From 59cbf791a180d2c529aee6faa7930e8d04560652 Mon Sep 17 00:00:00 2001
From: Benedikt Kloss <bene.kloss@gmail.com>
Date: Fri, 2 Feb 2024 06:57:21 -0500
Subject: [PATCH] Fix DMRG variational apply test and type signature in type
 definition.

---
 src/treetensornetworks/projttns/projouterprodttn.jl        | 4 +++-
 src/treetensornetworks/projttns/projttnsum.jl              | 6 +++---
 test/test_treetensornetworks/test_solvers/test_contract.jl | 4 ++++
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/treetensornetworks/projttns/projouterprodttn.jl b/src/treetensornetworks/projttns/projouterprodttn.jl
index 3052e0bd..27f532e6 100644
--- a/src/treetensornetworks/projttns/projouterprodttn.jl
+++ b/src/treetensornetworks/projttns/projouterprodttn.jl
@@ -106,6 +106,8 @@ function contract_ket(P::ProjOuterProdTTN, v::ITensor)
   return v
 end
 
+# ToDo: debug this, not yet working
+# probably 
 function contract(P::ProjOuterProdTTN, x::ITensor)
-  return conj(contract_ket(P, x)) * contract_ket(P, ITensor(true))
+  return conj(contract_ket(P, dag(x))) * contract_ket(P, ITensor(true))
 end
diff --git a/src/treetensornetworks/projttns/projttnsum.jl b/src/treetensornetworks/projttns/projttnsum.jl
index cd1cdf72..31eed8f5 100644
--- a/src/treetensornetworks/projttns/projttnsum.jl
+++ b/src/treetensornetworks/projttns/projttnsum.jl
@@ -2,9 +2,9 @@
 ProjTTNSum
 """
 struct ProjTTNSum{V} <: AbstractProjTTN{V}
-  terms::Vector{AbstractProjTTN{V}}
-  function ProjTTNSum(terms::Vector{<:AbstractProjTTN})
-    return new{eltype(terms)}(terms)
+  terms::Vector{T} where {T<:AbstractProjTTN{V}}
+  function ProjTTNSum(terms::Vector{T}) where {V,T<:AbstractProjTTN{V}}
+    return new{V}(terms)
   end
 end
 
diff --git a/test/test_treetensornetworks/test_solvers/test_contract.jl b/test/test_treetensornetworks/test_solvers/test_contract.jl
index 46eadf11..4be8a574 100644
--- a/test/test_treetensornetworks/test_solvers/test_contract.jl
+++ b/test/test_treetensornetworks/test_solvers/test_contract.jl
@@ -24,6 +24,10 @@ using Test
   # Test basic usage with default parameters
   Hpsi = apply(H, psi; alg="fit", init=psi, nsweeps=1)
   @test inner(psi, Hpsi) ≈ inner(psi', H, psi) atol = 1E-5
+  # Test variational compression via DMRG
+  Hfit = ProjOuterProdTTN(psi', H)
+  Hpsi_via_dmrg = dmrg(Hfit, psi; updater_kwargs=(; which_eigval=:LR,), nsweeps=1)
+  @test abs(inner(Hpsi_via_dmrg, Hpsi / norm(Hpsi))) ≈ 1 atol = 1E-4
 
   # Test basic usage for use with multiple ProjOuterProdTTN with default parameters
   # BLAS.axpy-like test