Remove bond s normalization in FET

Author: Yue-Zhengyuan

src/algorithms/truncation/fullenv_truncation.jl

@@ -230,8 +230,6 @@ function fullenv_truncate(
     # initialize u, s, vh with truncated or untruncated SVD
     u, s, vh = svd_trunc(b0; trunc = (alg.trunc_init ? alg.trunc : notrunc()))
     b1 = similar(b0)
-    # normalize `s` (bond matrices can always be normalized)
-    s /= norm(s, Inf)
     s0 = deepcopy(s)
     Δfid, Δs, fid, fid0 = NaN, NaN, 0.0, 0.0
     for iter in 1:(alg.maxiter)
@@ -245,7 +243,6 @@ function fullenv_truncate(
         r, info_r = linsolve(Base.Fix1(*, B), p, r, 0, 1)
         @tensor b1[-1; -2] = u[-1; 1] * r[1 -2]
         u, s, vh = svd_trunc(b1; trunc = alg.trunc)
-        s /= norm(s, Inf)
         # update `- l ←  =  - u ← s ←`
         @tensor l[-1 -2] := u[-1; 1] * s[1; -2]
         @tensor p[-1 -2] := conj(vh[-2; 2]) * benv[-1 2; 3 4] * b0[3; 4]
@@ -257,9 +254,9 @@ function fullenv_truncate(
         @tensor b1[-1; -2] = l[-1 1] * vh[1; -2]
         fid = fidelity(benv, b0, b1)
         u, s, vh = svd_trunc!(b1; trunc = alg.trunc)
-        s /= norm(s, Inf)
         # determine convergence
-        Δs = (space(s) == space(s0)) ? _singular_value_distance((s, s0)) : NaN
+        Δs = (space(s) == space(s0)) ? 
+            _singular_value_distance((normalize(s, Inf), normalize(s0, Inf))) : NaN
         Δfid = fid - fid0
         s0 = deepcopy(s)
         fid0 = fid

test/bondenv/bond_truncate.jl

@@ -7,7 +7,7 @@ using LinearAlgebra
 using KrylovKit
 
 Random.seed!(0)
-maxiter = 500
+maxiter = 600
 check_interval = 20
 trunc = truncerror(; atol = 1.0e-10) & truncrank(8)
 Vext = Vect[FermionParity](0 => 100, 1 => 100)
@@ -39,5 +39,5 @@ for Vbondl in (Vint, Vint'), Vbondr in (Vint, Vint')
         @test info.fid ≈ PEPSKit.fidelity(benv, PEPSKit._combine_ab(a1, b1), a2b2)
         @test info.fid > fid0
     end
-    @test isapprox(normalize(ss["ALS"], Inf), ss["FET"], atol = 1.0e-3)
+    @test isapprox(ss["ALS"], ss["FET"], atol = 1.0e-3)
 end