From 73680b6e0ba7419427f4ff50f471c073ed94763e Mon Sep 17 00:00:00 2001
From: Joey <joeytindall94@googlemail.com>
Date: Wed, 20 Mar 2024 10:30:30 +0000
Subject: [PATCH] Derivative -> Environment

---
 src/ITensorNetworks.jl                  |  2 +-
 src/caches/beliefpropagationcache.jl    |  2 --
 src/{derivative.jl => environment.jl}   | 15 +++++++++------
 src/formnetworks/abstractformnetwork.jl | 12 ++++++------
 test/test_forms.jl                      |  8 ++++----
 5 files changed, 20 insertions(+), 19 deletions(-)
 rename src/{derivative.jl => environment.jl} (74%)

diff --git a/src/ITensorNetworks.jl b/src/ITensorNetworks.jl
index 9e81a3e6..536db27c 100644
--- a/src/ITensorNetworks.jl
+++ b/src/ITensorNetworks.jl
@@ -129,7 +129,7 @@ include(joinpath("treetensornetworks", "solvers", "contract.jl"))
 include(joinpath("treetensornetworks", "solvers", "linsolve.jl"))
 include(joinpath("treetensornetworks", "solvers", "tree_sweeping.jl"))
 include("apply.jl")
-include("derivative.jl")
+include("environment.jl")
 
 include("exports.jl")
 
diff --git a/src/caches/beliefpropagationcache.jl b/src/caches/beliefpropagationcache.jl
index ab6204b5..92f761c2 100644
--- a/src/caches/beliefpropagationcache.jl
+++ b/src/caches/beliefpropagationcache.jl
@@ -11,8 +11,6 @@ end
   return default_bp_maxiter(undirected_graph(underlying_graph(g)))
 end
 default_partitioning(ψ::AbstractITensorNetwork) = group(v -> v, vertices(ψ))
-#We could probably do something cleverer here based on graph partitioning algorithms: https://en.wikipedia.org/wiki/Graph_partition.
-default_partitioning(f::AbstractFormNetwork) = group(v -> state_vertex(f, v), vertices(f))
 default_cache_update_kwargs(cache) = (; maxiter=20, tol=1e-5)
 
 function message_diff(message_a::Vector{ITensor}, message_b::Vector{ITensor})
diff --git a/src/derivative.jl b/src/environment.jl
similarity index 74%
rename from src/derivative.jl
rename to src/environment.jl
index 4acbd1a8..7d1c2ef1 100644
--- a/src/derivative.jl
+++ b/src/environment.jl
@@ -1,12 +1,15 @@
-default_derivative_algorithm() = "exact"
+default_environment_algorithm() = "exact"
 
-function derivative(
-  ψ::AbstractITensorNetwork, vertices::Vector; alg=default_derivative_algorithm(), kwargs...
+function environment(
+  ψ::AbstractITensorNetwork,
+  vertices::Vector;
+  alg=default_environment_algorithm(),
+  kwargs...,
 )
-  return derivative(Algorithm(alg), ψ, vertices; kwargs...)
+  return environment(Algorithm(alg), ψ, vertices; kwargs...)
 end
 
-function derivative(
+function environment(
   ::Algorithm"exact",
   ψ::AbstractITensorNetwork,
   vertices::Vector;
@@ -18,7 +21,7 @@ function derivative(
   return ITensor[contract(ψ_reduced; sequence, kwargs...)]
 end
 
-function derivative(
+function environment(
   ::Algorithm"bp",
   ψ::AbstractITensorNetwork,
   verts::Vector;
diff --git a/src/formnetworks/abstractformnetwork.jl b/src/formnetworks/abstractformnetwork.jl
index 66b395ad..07a2a0fd 100644
--- a/src/formnetworks/abstractformnetwork.jl
+++ b/src/formnetworks/abstractformnetwork.jl
@@ -57,22 +57,22 @@ function operator_network(f::AbstractFormNetwork)
   )
 end
 
-function derivative(
+function environment(
   f::AbstractFormNetwork,
   state_vertices::Vector;
-  alg=default_derivative_algorithm(),
+  alg=default_environment_algorithm(),
   kwargs...,
 )
-  tn_vertices = derivative_vertices(f, state_vertices)
+  tn_vertices = environment_vertices(f, state_vertices)
   if alg == "bp"
     partitions = group(v -> state_vertex(f, v), vertices(f))
-    return derivative(tensornetwork(f), tn_vertices; alg, partitions, kwargs...)
+    return environment(tensornetwork(f), tn_vertices; alg, partitions, kwargs...)
   else
-    return derivative(tensornetwork(f), tn_vertices; alg, kwargs...)
+    return environment(tensornetwork(f), tn_vertices; alg, kwargs...)
   end
 end
 
-function derivative_vertices(f::AbstractFormNetwork, state_vertices::Vector; kwargs...)
+function environment_vertices(f::AbstractFormNetwork, state_vertices::Vector; kwargs...)
   return setdiff(
     vertices(f), vcat(bra_vertices(f, state_vertices), ket_vertices(f, state_vertices))
   )
diff --git a/test/test_forms.jl b/test/test_forms.jl
index 63686336..0bfa2d02 100644
--- a/test/test_forms.jl
+++ b/test/test_forms.jl
@@ -12,7 +12,7 @@ using ITensorNetworks:
   bra_network,
   ket_network,
   operator_network,
-  derivative,
+  environment,
   BeliefPropagationCache
 using Test
 using Random
@@ -52,16 +52,16 @@ using SplitApplyCombine
   @test underlying_graph(ket_network(qf)) == underlying_graph(ψket)
   @test underlying_graph(operator_network(qf)) == underlying_graph(A)
 
-  ∂qf_∂v = only(derivative(qf, [v]))
+  ∂qf_∂v = only(environment(qf, [v]))
   @test (∂qf_∂v) * (qf[ket_vertex(qf, v)] * qf[bra_vertex(qf, v)]) ≈ contract(qf)
 
-  ∂qf_∂v_bp = derivative(qf, [v]; alg="bp", update_cache=false)
+  ∂qf_∂v_bp = environment(qf, [v]; alg="bp", update_cache=false)
   ∂qf_∂v_bp = contract(∂qf_∂v_bp)
   ∂qf_∂v_bp /= norm(∂qf_∂v_bp)
   ∂qf_∂v /= norm(∂qf_∂v)
   @test ∂qf_∂v_bp != ∂qf_∂v
 
-  ∂qf_∂v_bp = derivative(qf, [v]; alg="bp", update_cache=true)
+  ∂qf_∂v_bp = environment(qf, [v]; alg="bp", update_cache=true)
   ∂qf_∂v_bp = contract(∂qf_∂v_bp)
   ∂qf_∂v_bp /= norm(∂qf_∂v_bp)
   @test ∂qf_∂v_bp ≈ ∂qf_∂v