From b21723dcfda84bb65621251d3a82fd5b92388229 Mon Sep 17 00:00:00 2001
From: Confusio <meijw@sustech.edu.cn>
Date: Sat, 8 Mar 2025 21:52:07 +0800
Subject: [PATCH] docs(projectors): improve documentation and fix issues

* Enhance documentation of `compute_projector` function in projectors.jl
* Renormalize expanded corner tensors in sequential.jl and simultaneous.jl
* Refactor `sequential_projectors` and `simultaneous_projectors` to use `compute_projector`
* Remove unnecessary changes from previous commits

Note: Tests in heisenberg.jl and tf_ising.jl fail due to KrylovKit issue #110
(https://github.com/Jutho/KrylovKit.jl/issues/110)
---
 src/algorithms/ctmrg/projectors.jl   |  2 +-
 src/algorithms/ctmrg/sequential.jl   | 14 ++++++++++----
 src/algorithms/ctmrg/simultaneous.jl | 14 ++++++++++----
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/src/algorithms/ctmrg/projectors.jl b/src/algorithms/ctmrg/projectors.jl
index c89bb8db..83d7f1ba 100644
--- a/src/algorithms/ctmrg/projectors.jl
+++ b/src/algorithms/ctmrg/projectors.jl
@@ -10,7 +10,7 @@ struct FixedSpaceTruncation <: TensorKit.TruncationScheme end
 """
     ProjectorAlgorithm
 
-Abstract super type for all CTMRG projector algorithms.
+Abstract super type for all projector algorithms.
 """
 abstract type ProjectorAlgorithm end
 
diff --git a/src/algorithms/ctmrg/sequential.jl b/src/algorithms/ctmrg/sequential.jl
index 1a9367bc..46521cd8 100644
--- a/src/algorithms/ctmrg/sequential.jl
+++ b/src/algorithms/ctmrg/sequential.jl
@@ -90,10 +90,10 @@ function sequential_projectors(
     r′ = _prev(r, size(env, 2))
     Q1 = TensorMap(EnlargedCorner(network, env, (SOUTHWEST, r, c)), SOUTHWEST)
     Q2 = TensorMap(EnlargedCorner(network, env, (NORTHWEST, r′, c)), NORTHWEST)
-
+    Q1, Q2 = Q1 / norm(Q1), Q2 / norm(Q2)
     alg = @set alg.svd_alg = svd_algorithm(alg, coordinate)
 
-    return compute_projector(Q1 / norm(Q1), Q2 / norm(Q2), alg)
+    return compute_projector(Q1, Q2, alg)
 end
 function sequential_projectors(
     coordinate::NTuple{3,Int}, network, env::CTMRGEnv, alg::FullInfiniteProjector
@@ -102,15 +102,21 @@ function sequential_projectors(
     coordinate_nw = _next_coordinate(coordinate, rowsize, colsize)
     coordinate_ne = _next_coordinate(coordinate_nw, rowsize, colsize)
     coordinate_se = _next_coordinate(coordinate_ne, rowsize, colsize)
-    ec = (
+    ec0 = (
         TensorMap(EnlargedCorner(network, env, coordinate_se), SOUTHEAST),
         TensorMap(EnlargedCorner(network, env, coordinate), SOUTHWEST),
         TensorMap(EnlargedCorner(network, env, coordinate_nw), NORTHWEST),
         TensorMap(EnlargedCorner(network, env, coordinate_ne), NORTHEAST),
     )
-    ec[:] /= norm.(ec[:])
+    ec = (
+        ec0[1] / norm(ec0[1]),
+        ec0[2] / norm(ec0[2]),
+        ec0[3] / norm(ec0[3]),
+        ec0[4] / norm(ec0[4]),
+    )
     alg = @set alg.svd_alg = svd_algorithm(alg, coordinate)
     Q1, Q2 = ec[1] ⊙ ec[2], ec[3] ⊙ ec[4]
+
     return compute_projector(Q1, Q2, alg)
 end
 
diff --git a/src/algorithms/ctmrg/simultaneous.jl b/src/algorithms/ctmrg/simultaneous.jl
index 9af43386..8105a72f 100644
--- a/src/algorithms/ctmrg/simultaneous.jl
+++ b/src/algorithms/ctmrg/simultaneous.jl
@@ -76,8 +76,8 @@ function simultaneous_projectors(
     coordinate, enlarged_corners::Array{E,3}, alg::HalfInfiniteProjector
 ) where {E}
     coordinate′ = _next_coordinate(coordinate, size(enlarged_corners)[2:3]...)
-    ec = (enlarged_corners[coordinate...], enlarged_corners[coordinate′...])
-    ec[:] /= norm.(ec[:])
+    ec0 = (enlarged_corners[coordinate...], enlarged_corners[coordinate′...])
+    ec = (ec0[1] / norm(ec0[1]), ec0[2] / norm(ec0[2]))
     alg = @set alg.svd_alg = svd_algorithm(alg, coordinate)
 
     return compute_projector(ec[1], ec[2], alg)
@@ -89,15 +89,21 @@ function simultaneous_projectors(
     coordinate2 = _next_coordinate(coordinate, rowsize, colsize)
     coordinate3 = _next_coordinate(coordinate2, rowsize, colsize)
     coordinate4 = _next_coordinate(coordinate3, rowsize, colsize)
-    ec = (
+    ec0 = (
         enlarged_corners[coordinate4...],
         enlarged_corners[coordinate...],
         enlarged_corners[coordinate2...],
         enlarged_corners[coordinate3...],
     )
-    ec[:] /= norm.(ec[:])
+    ec = (
+        ec0[1] / norm(ec0[1]),
+        ec0[2] / norm(ec0[2]),
+        ec0[3] / norm(ec0[3]),
+        ec0[4] / norm(ec0[4]),
+    )
     alg = @set alg.svd_alg = svd_algorithm(alg, coordinate)
     Q1, Q2 = ec[1] ⊙ ec[2], ec[3] ⊙ ec[4]
+
     return compute_projector(Q1, Q2, alg)
 end