From 01643fe834f7f9a8388d5639ae82a9f85288cd3a Mon Sep 17 00:00:00 2001
From: Alec Edgington <54802828+cqc-alec@users.noreply.github.com>
Date: Wed, 27 Nov 2024 16:09:01 +0000
Subject: [PATCH] Only update index map when needed (#1697)

---
 pytket/conanfile.py                                         | 2 +-
 tket/conanfile.py                                           | 2 +-
 tket/include/tket/Transformations/CliffordReductionPass.hpp | 3 +++
 tket/src/Transformations/CliffordReductionPass.cpp          | 3 ++-
 4 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/pytket/conanfile.py b/pytket/conanfile.py
index 9bdd4157ce..cc9ab6c313 100644
--- a/pytket/conanfile.py
+++ b/pytket/conanfile.py
@@ -38,7 +38,7 @@ def requirements(self):
         self.requires("pybind11_json/0.2.14")
         self.requires("symengine/0.13.0")
         self.requires("tkassert/0.3.4@tket/stable")
-        self.requires("tket/1.3.50@tket/stable")
+        self.requires("tket/1.3.51@tket/stable")
         self.requires("tklog/0.3.3@tket/stable")
         self.requires("tkrng/0.3.3@tket/stable")
         self.requires("tktokenswap/0.3.9@tket/stable")
diff --git a/tket/conanfile.py b/tket/conanfile.py
index da3643e863..8e330a0a69 100644
--- a/tket/conanfile.py
+++ b/tket/conanfile.py
@@ -23,7 +23,7 @@
 
 class TketConan(ConanFile):
     name = "tket"
-    version = "1.3.50"
+    version = "1.3.51"
     package_type = "library"
     license = "Apache 2"
     homepage = "https://github.com/CQCL/tket"
diff --git a/tket/include/tket/Transformations/CliffordReductionPass.hpp b/tket/include/tket/Transformations/CliffordReductionPass.hpp
index 71fc6c3dd5..eeb27545f6 100644
--- a/tket/include/tket/Transformations/CliffordReductionPass.hpp
+++ b/tket/include/tket/Transformations/CliffordReductionPass.hpp
@@ -112,6 +112,9 @@ class CliffordReductionPass {
   /** The circuit under transformation */
   Circuit &circ;
 
+  /** Topological-order-respecting map from circuit vertices to integers */
+  IndexMap im;
+
   /** Table of potential transports of 2qb interactions through the circuit */
   interaction_table_t itable;
 
diff --git a/tket/src/Transformations/CliffordReductionPass.cpp b/tket/src/Transformations/CliffordReductionPass.cpp
index 8efd3b2ec9..65934205b9 100644
--- a/tket/src/Transformations/CliffordReductionPass.cpp
+++ b/tket/src/Transformations/CliffordReductionPass.cpp
@@ -234,7 +234,6 @@ std::optional<InteractionMatch> CliffordReductionPass::search_back_for_match(
   point[0] = rip0;
   point[1] = rip1;
   std::map<Edge, RevInteractionPoint> point_lookup;
-  IndexMap im = circ.index_map();
 
   // interactions met when commuting back; point lists are in causal order of
   // circuit:
@@ -350,6 +349,7 @@ void CliffordReductionPass::process_new_interaction(const Vertex &inter) {
           break;
         }
       }
+      im = circ.index_map();
       success = true;
     } else {
       std::vector<std::optional<Edge>> outs = circ.get_linear_out_edges(v);
@@ -645,6 +645,7 @@ CliffordReductionPass::valid_insertion_point(
 
 CliffordReductionPass::CliffordReductionPass(Circuit &c, bool swaps)
     : circ(c),
+      im(c.index_map()),
       itable(),
       v_to_depth(),
       success(false),