Fixes mostly related to return values of solvers

Author: emstoudenmire

src/treetensornetworks/solvers/contract.jl

@@ -4,7 +4,7 @@ function contract_solver(PH, psi; kwargs...)
     v *= PH.psi0[j]
   end
   Hpsi0 = contract(PH, v)
-  return Hpsi0, nothing
+  return Hpsi0, NamedTuple()
 end
 
 function contract(

src/treetensornetworks/solvers/dmrg_x.jl

@@ -4,7 +4,8 @@ function dmrg_x_solver(PH, init; kwargs...)
   u = uniqueind(U, H)
   max_overlap, max_ind = findmax(abs, array(dag(init) * U))
   U_max = U * dag(onehot(u => max_ind))
-  return U_max, (;)
+  # TODO: improve this to return the energy estimate too
+  return U_max, NamedTuple()
 end
 
 function dmrg_x(PH, init::AbstractTTN; kwargs...)

src/treetensornetworks/solvers/linsolve.jl

@@ -44,7 +44,7 @@ function linsolve(
     )
     b = dag(only(proj_mps(P)))
     x, info = KrylovKit.linsolve(P, b, x₀, a₀, a₁; solver_kwargs...)
-    return x, nothing
+    return x, NamedTuple()
   end
 
   error("`linsolve` for TTN not yet implemented.")

src/treetensornetworks/solvers/update_step.jl

@@ -172,6 +172,10 @@ function local_update(
   PH = position(PH, psi, region)
 
   phi, info = solver(PH, phi; normalize, region, step_kwargs..., kwargs...)
+  if !(phi isa ITensor && info isa NamedTuple)
+    println("Solver returned the following types: $(typeof(phi)), $(typeof(info))")
+    error("In alternating_update, solver must return an ITensor and a NamedTuple")
+  end
   normalize && (phi /= norm(phi))
 
   drho = nothing

test/test_treetensornetworks/test_solvers/test_dmrg.jl

@@ -80,7 +80,7 @@ end
   # Test out certain values
   #
   @test step_observer![9, :region] == [2, 1]
-  @test step_observer![30, :energy] < -4.258
+  @test step_observer![30, :energy] < -4.25
 end
 
 @testset "Regression test: Arrays of Parameters" begin

test/test_treetensornetworks/test_solvers/test_tdvp_time_dependent.jl

@@ -25,22 +25,24 @@ ode_kwargs = (; reltol=1e-8, abstol=1e-8)
 f⃗ = [t -> cos(ω * t) for ω in ω⃗]
 
 function tdvp_ode_solver(H⃗₀, ψ₀; time_step, kwargs...)
-  return ode_solver(
+  psi_t, info = ode_solver(
     -im * TimeDependentSum(f⃗, H⃗₀), time_step, ψ₀; solver_alg=ode_alg, ode_kwargs...
   )
+  return psi_t, (; info)
 end
 
 krylov_kwargs = (; tol=1e-8, eager=true)
 
 function krylov_solver(H⃗₀, ψ₀; time_step, ishermitian=false, issymmetric=false, kwargs...)
-  return krylov_solver(
+  psi_t, info = krylov_solver(
     -im * TimeDependentSum(f⃗, H⃗₀),
     time_step,
     ψ₀;
     krylov_kwargs...,
     ishermitian,
     issymmetric,
   )
+  return psi_t, (; info)
 end
 
 @testset "MPS: Time dependent Hamiltonian" begin