Test timestep for NTU

Author: Yue-Zhengyuan

test/timeevol/timestep.jl

@@ -3,14 +3,16 @@ using Random
 using TensorKit
 using PEPSKit
 
+Nr, Nc = 2, 2
+H = real(heisenberg_XYZ(ComplexF64, Trivial, InfiniteSquare(Nr, Nc); Jx = 1, Jy = 1, Jz = 1))
+Pspace, Vspace = ℂ^2, ℂ^4
+ψ0 = InfinitePEPS(rand, Float64, Pspace, Vspace; unitcell = (Nr, Nc))
+dt, nstep = 0.1, 20
+trunc = truncerror(; atol = 1.0e-10) & truncrank(4)
+
 @testset "SimpleUpdate timestep" begin
-    Nr, Nc = 2, 2
-    H = real(heisenberg_XYZ(ComplexF64, Trivial, InfiniteSquare(Nr, Nc); Jx = 1, Jy = 1, Jz = 1))
-    Pspace, Vspace = ℂ^2, ℂ^4
-    ψ0 = InfinitePEPS(rand, Float64, Pspace, Vspace; unitcell = (Nr, Nc))
+    alg = SimpleUpdate(; trunc)
     env0 = SUWeight(ψ0)
-    alg = SimpleUpdate(; trunc = truncerror(; atol = 1.0e-10) & truncrank(4))
-    dt, nstep = 1.0e-2, 50
     # manual timestep
     evolver = TimeEvolver(ψ0, H, dt, nstep, alg, env0)
     ψ1, env1, info1 = deepcopy(ψ0), deepcopy(env0), nothing
@@ -31,3 +33,25 @@ using PEPSKit
     @test env1 == env2 == env3
     @test info1 == info2 == info3
 end
+
+@testset "NeighbourUpdate timestep" begin
+    alg = NeighbourUpdate(; opt_alg = ALSTruncation(; trunc))
+    # manual timestep
+    evolver = TimeEvolver(ψ0, H, dt, nstep, alg)
+    ψ1, info1 = deepcopy(ψ0), nothing
+    for iter in 0:(nstep - 1)
+        ψ1, info1 = timestep(evolver, ψ1)
+    end
+    # time_evolve
+    ψ2, info2 = time_evolve(ψ0, H, dt, nstep, alg)
+    # for-loop syntax
+    ## manually reset internal state of evolver
+    evolver.state = PEPSKit.NTUState(0, 0.0, ψ0)
+    ψ3, info3 = nothing, nothing, nothing
+    for state in evolver
+        ψ3, info3 = state
+    end
+    # results should be *exactly* the same
+    @test ψ1 == ψ2 == ψ3
+    @test info1 == info2 == info3
+end