From a915cd5ca2f45628d56c7f43902f64d3ae5b45d7 Mon Sep 17 00:00:00 2001
From: DrTVockerodtMO <114994380+DrTVockerodtMO@users.noreply.github.com>
Date: Thu, 24 Sep 2026 14:40:25 +0100
Subject: [PATCH 1/9] Spawn branch


From c498e55b203d0f1b0f19a89b011d5248fbb08c64 Mon Sep 17 00:00:00 2001
From: DrTVockerodtMO <114994380+DrTVockerodtMO@users.noreply.github.com>
Date: Thu, 24 Sep 2026 14:55:20 +0100
Subject: [PATCH 2/9] Added empty Norm

---
 src/orca-jedi/CMakeLists.txt              |  2 +
 src/orca-jedi/norm/Norm.cc                | 39 ++++++++++++++++++
 src/orca-jedi/norm/Norm.h                 | 48 +++++++++++++++++++++++
 src/orca-jedi/utilities/OrcaModelTraits.h |  2 +
 4 files changed, 91 insertions(+)
 create mode 100644 src/orca-jedi/norm/Norm.cc
 create mode 100644 src/orca-jedi/norm/Norm.h

diff --git a/src/orca-jedi/CMakeLists.txt b/src/orca-jedi/CMakeLists.txt
index 39bee20a..0f60b529 100644
--- a/src/orca-jedi/CMakeLists.txt
+++ b/src/orca-jedi/CMakeLists.txt
@@ -20,6 +20,8 @@ model/ModelBiasCovariance.h
 model/ModelBias.h
 model/ModelBiasIncrement.h
 model/Model.h
+norm/Norm.h
+norm/Norm.cc
 state/State.h
 state/State.cc
 nemo_io/NemoFieldReader.h
diff --git a/src/orca-jedi/norm/Norm.cc b/src/orca-jedi/norm/Norm.cc
new file mode 100644
index 00000000..ad7c08ff
--- /dev/null
+++ b/src/orca-jedi/norm/Norm.cc
@@ -0,0 +1,39 @@
+/*
+ * (C) British Crown Copyright 2026 Met Office
+ *
+ * This software is licensed under the terms of the Apache Licence Version 2.0
+ * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
+ */
+
+#include "orca-jedi/norm/Norm.h"
+
+#include "eckit/exception/Exceptions.h"
+
+namespace orcamodel {
+
+Norm::Norm(const Geometry & resol,
+           const oops::Variables & vars,
+           const util::DateTime & validTime,
+           const eckit::Configuration & conf) {
+  throw eckit::NotImplemented(Here());
+}
+
+Norm::~Norm() {}
+
+void Norm::calculate(const State & xx) {
+  throw eckit::NotImplemented(Here());
+}
+
+void Norm::apply(Increment & dx) const {
+  throw eckit::NotImplemented(Here());
+}
+
+void Norm::applyInverse(Increment & dx) const {
+  throw eckit::NotImplemented(Here());
+}
+
+void Norm::print(std::ostream & os) const {
+  throw eckit::NotImplemented(Here());
+}
+
+}  // namespace orcamodel
diff --git a/src/orca-jedi/norm/Norm.h b/src/orca-jedi/norm/Norm.h
new file mode 100644
index 00000000..c2f9f110
--- /dev/null
+++ b/src/orca-jedi/norm/Norm.h
@@ -0,0 +1,48 @@
+/*
+ * (C) British Crown Copyright 2026 Met Office
+ *
+ * This software is licensed under the terms of the Apache Licence Version 2.0
+ * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
+ */
+
+#pragma once
+
+#include <string>
+
+#include "eckit/config/Configuration.h"
+
+#include "oops/base/Variables.h"
+#include "oops/util/DateTime.h"
+#include "oops/util/ObjectCounter.h"
+#include "oops/util/Printable.h"
+
+#include "orca-jedi/geometry/Geometry.h"
+#include "orca-jedi/increment/Increment.h"
+#include "orca-jedi/state/State.h"
+
+namespace orcamodel {
+
+class Norm : public util::Printable,
+             private util::ObjectCounter<Norm> {
+ public:
+  static const std::string classname() {return "orcamodel::Norm";}
+
+// Constructor, destructor
+  Norm(const Geometry &,
+       const oops::Variables &,
+       const util::DateTime &,
+       const eckit::Configuration &);
+  ~Norm();
+
+// Compute values for norm
+  void calculate(const State &);
+
+// Apply norm to increment
+  void apply(Increment &) const;
+  void applyInverse(Increment &) const;
+
+ private:
+  void print(std::ostream &) const override;
+};
+
+}  // namespace orcamodel
diff --git a/src/orca-jedi/utilities/OrcaModelTraits.h b/src/orca-jedi/utilities/OrcaModelTraits.h
index d9a2b33e..02f7ef5c 100644
--- a/src/orca-jedi/utilities/OrcaModelTraits.h
+++ b/src/orca-jedi/utilities/OrcaModelTraits.h
@@ -16,6 +16,7 @@
 #include "orca-jedi/model/ModelBias.h"
 #include "orca-jedi/model/ModelBiasIncrement.h"
 #include "orca-jedi/model/ModelBiasCovariance.h"
+#include "orca-jedi/norm/Norm.h"
 #include "orca-jedi/state/State.h"
 #include "orca-jedi/utilities/ModelData.h"
 #include "orca-jedi/variablechanges/VariableChange.h"
@@ -38,6 +39,7 @@ struct OrcaModelTraits {
   typedef orcamodel::ModelBiasIncrement        ModelAuxIncrement;
   typedef orcamodel::ModelBiasCovariance       ModelAuxCovariance;
   typedef orcamodel::Model                     Model;
+  typedef orcamodel::Norm                      Norm;
   typedef orcamodel::State                     State;
   typedef orcamodel::LinearModel               LinearModel;
   typedef orcamodel::VariableChange            VariableChange;

From 3c22e4bf41f4917c3796b6d487e260bf0dd84f4e Mon Sep 17 00:00:00 2001
From: DrTVockerodtMO <114994380+DrTVockerodtMO@users.noreply.github.com>
Date: Wed, 30 Sep 2026 13:46:10 +0100
Subject: [PATCH 3/9] Simplified interface

---
 src/orca-jedi/norm/Norm.cc | 4 +---
 src/orca-jedi/norm/Norm.h  | 6 +-----
 2 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/src/orca-jedi/norm/Norm.cc b/src/orca-jedi/norm/Norm.cc
index ad7c08ff..2d6607f1 100644
--- a/src/orca-jedi/norm/Norm.cc
+++ b/src/orca-jedi/norm/Norm.cc
@@ -11,9 +11,7 @@
 
 namespace orcamodel {
 
-Norm::Norm(const Geometry & resol,
-           const oops::Variables & vars,
-           const util::DateTime & validTime,
+Norm::Norm(const oops::Variables & vars,
            const eckit::Configuration & conf) {
   throw eckit::NotImplemented(Here());
 }
diff --git a/src/orca-jedi/norm/Norm.h b/src/orca-jedi/norm/Norm.h
index c2f9f110..e16fbe6b 100644
--- a/src/orca-jedi/norm/Norm.h
+++ b/src/orca-jedi/norm/Norm.h
@@ -12,11 +12,9 @@
 #include "eckit/config/Configuration.h"
 
 #include "oops/base/Variables.h"
-#include "oops/util/DateTime.h"
 #include "oops/util/ObjectCounter.h"
 #include "oops/util/Printable.h"
 
-#include "orca-jedi/geometry/Geometry.h"
 #include "orca-jedi/increment/Increment.h"
 #include "orca-jedi/state/State.h"
 
@@ -28,9 +26,7 @@ class Norm : public util::Printable,
   static const std::string classname() {return "orcamodel::Norm";}
 
 // Constructor, destructor
-  Norm(const Geometry &,
-       const oops::Variables &,
-       const util::DateTime &,
+  Norm(const oops::Variables &,
        const eckit::Configuration &);
   ~Norm();
 

From 0aadc6642b08ef20a7da579ad89dd5cc5bff980c Mon Sep 17 00:00:00 2001
From: DrTVockerodtMO <114994380+DrTVockerodtMO@users.noreply.github.com>
Date: Wed, 7 Oct 2026 14:29:54 +0100
Subject: [PATCH 4/9] Used default destructor

---
 src/orca-jedi/norm/Norm.cc | 2 --
 src/orca-jedi/norm/Norm.h  | 2 +-
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/orca-jedi/norm/Norm.cc b/src/orca-jedi/norm/Norm.cc
index 2d6607f1..f5174347 100644
--- a/src/orca-jedi/norm/Norm.cc
+++ b/src/orca-jedi/norm/Norm.cc
@@ -16,8 +16,6 @@ Norm::Norm(const oops::Variables & vars,
   throw eckit::NotImplemented(Here());
 }
 
-Norm::~Norm() {}
-
 void Norm::calculate(const State & xx) {
   throw eckit::NotImplemented(Here());
 }
diff --git a/src/orca-jedi/norm/Norm.h b/src/orca-jedi/norm/Norm.h
index e16fbe6b..3eb76a56 100644
--- a/src/orca-jedi/norm/Norm.h
+++ b/src/orca-jedi/norm/Norm.h
@@ -28,7 +28,7 @@ class Norm : public util::Printable,
 // Constructor, destructor
   Norm(const oops::Variables &,
        const eckit::Configuration &);
-  ~Norm();
+  ~Norm() = default;
 
 // Compute values for norm
   void calculate(const State &);

From ceafc90f509af3fc9bca6934218aeb2f7dc07deb Mon Sep 17 00:00:00 2001
From: DrTVockerodtMO <114994380+DrTVockerodtMO@users.noreply.github.com>
Date: Fri, 9 Oct 2026 09:28:26 +0100
Subject: [PATCH 5/9] Removed unused variable names

---
 src/orca-jedi/norm/Norm.cc | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/orca-jedi/norm/Norm.cc b/src/orca-jedi/norm/Norm.cc
index f5174347..9aa81633 100644
--- a/src/orca-jedi/norm/Norm.cc
+++ b/src/orca-jedi/norm/Norm.cc
@@ -11,24 +11,24 @@
 
 namespace orcamodel {
 
-Norm::Norm(const oops::Variables & vars,
-           const eckit::Configuration & conf) {
+Norm::Norm(const oops::Variables &,
+           const eckit::Configuration &) {
   throw eckit::NotImplemented(Here());
 }
 
-void Norm::calculate(const State & xx) {
+void Norm::calculate(const State &) {
   throw eckit::NotImplemented(Here());
 }
 
-void Norm::apply(Increment & dx) const {
+void Norm::apply(Increment &) const {
   throw eckit::NotImplemented(Here());
 }
 
-void Norm::applyInverse(Increment & dx) const {
+void Norm::applyInverse(Increment &) const {
   throw eckit::NotImplemented(Here());
 }
 
-void Norm::print(std::ostream & os) const {
+void Norm::print(std::ostream &) const {
   throw eckit::NotImplemented(Here());
 }
 

From 8cbfb2e4864e8e6da6402e26d0b976fcc75784f8 Mon Sep 17 00:00:00 2001
From: DrTVockerodtMO <114994380+DrTVockerodtMO@users.noreply.github.com>
Date: Fri, 16 Oct 2026 08:50:51 +0100
Subject: [PATCH 6/9] Moved state to constructor

---
 src/orca-jedi/norm/Norm.cc | 7 ++-----
 src/orca-jedi/norm/Norm.h  | 6 ++----
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/src/orca-jedi/norm/Norm.cc b/src/orca-jedi/norm/Norm.cc
index 9aa81633..d3e6c7b3 100644
--- a/src/orca-jedi/norm/Norm.cc
+++ b/src/orca-jedi/norm/Norm.cc
@@ -12,11 +12,8 @@
 namespace orcamodel {
 
 Norm::Norm(const oops::Variables &,
-           const eckit::Configuration &) {
-  throw eckit::NotImplemented(Here());
-}
-
-void Norm::calculate(const State &) {
+           const eckit::Configuration &,
+           const State &) {
   throw eckit::NotImplemented(Here());
 }
 
diff --git a/src/orca-jedi/norm/Norm.h b/src/orca-jedi/norm/Norm.h
index 3eb76a56..0cb0b045 100644
--- a/src/orca-jedi/norm/Norm.h
+++ b/src/orca-jedi/norm/Norm.h
@@ -27,12 +27,10 @@ class Norm : public util::Printable,
 
 // Constructor, destructor
   Norm(const oops::Variables &,
-       const eckit::Configuration &);
+       const eckit::Configuration &,
+       const State &);
   ~Norm() = default;
 
-// Compute values for norm
-  void calculate(const State &);
-
 // Apply norm to increment
   void apply(Increment &) const;
   void applyInverse(Increment &) const;

From 8a2fea1775eadfd19476f6fa4486f9d16a9cd583 Mon Sep 17 00:00:00 2001
From: DrTVockerodtMO <114994380+DrTVockerodtMO@users.noreply.github.com>
Date: Wed, 28 Oct 2026 08:18:34 +0000
Subject: [PATCH 7/9] Update interface

---
 src/orca-jedi/norm/Norm.cc | 4 ++++
 src/orca-jedi/norm/Norm.h  | 1 +
 2 files changed, 5 insertions(+)

diff --git a/src/orca-jedi/norm/Norm.cc b/src/orca-jedi/norm/Norm.cc
index d3e6c7b3..72f16887 100644
--- a/src/orca-jedi/norm/Norm.cc
+++ b/src/orca-jedi/norm/Norm.cc
@@ -25,6 +25,10 @@ void Norm::applyInverse(Increment &) const {
   throw eckit::NotImplemented(Here());
 }
 
+const double Norm::computeNorm(Increment &) const {
+  throw eckit::NotImplemented(Here());
+}
+
 void Norm::print(std::ostream &) const {
   throw eckit::NotImplemented(Here());
 }
diff --git a/src/orca-jedi/norm/Norm.h b/src/orca-jedi/norm/Norm.h
index 0cb0b045..b9b6430f 100644
--- a/src/orca-jedi/norm/Norm.h
+++ b/src/orca-jedi/norm/Norm.h
@@ -34,6 +34,7 @@ class Norm : public util::Printable,
 // Apply norm to increment
   void apply(Increment &) const;
   void applyInverse(Increment &) const;
+  const double computeNorm(Increment &) const;
 
  private:
   void print(std::ostream &) const override;

From f8660c8afb377d28ea091d4b8bfa7dcc886f6f66 Mon Sep 17 00:00:00 2001
From: DrTVockerodtMO <114994380+DrTVockerodtMO@users.noreply.github.com>
Date: Wed, 28 Oct 2026 08:24:33 +0000
Subject: [PATCH 8/9] Should be const

---
 src/orca-jedi/norm/Norm.cc | 2 +-
 src/orca-jedi/norm/Norm.h  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/orca-jedi/norm/Norm.cc b/src/orca-jedi/norm/Norm.cc
index 72f16887..13f61f85 100644
--- a/src/orca-jedi/norm/Norm.cc
+++ b/src/orca-jedi/norm/Norm.cc
@@ -25,7 +25,7 @@ void Norm::applyInverse(Increment &) const {
   throw eckit::NotImplemented(Here());
 }
 
-const double Norm::computeNorm(Increment &) const {
+const double Norm::computeNorm(const Increment &) const {
   throw eckit::NotImplemented(Here());
 }
 
diff --git a/src/orca-jedi/norm/Norm.h b/src/orca-jedi/norm/Norm.h
index b9b6430f..3e96ff7e 100644
--- a/src/orca-jedi/norm/Norm.h
+++ b/src/orca-jedi/norm/Norm.h
@@ -34,7 +34,7 @@ class Norm : public util::Printable,
 // Apply norm to increment
   void apply(Increment &) const;
   void applyInverse(Increment &) const;
-  const double computeNorm(Increment &) const;
+  const double computeNorm(const Increment &) const;
 
  private:
   void print(std::ostream &) const override;

From fd3cc7a97cf53f720c9141a9fedb6cacae042182 Mon Sep 17 00:00:00 2001
From: DrTVockerodtMO <114994380+DrTVockerodtMO@users.noreply.github.com>
Date: Wed, 28 Oct 2026 08:46:00 +0000
Subject: [PATCH 9/9] Add return

---
 src/orca-jedi/norm/Norm.cc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/orca-jedi/norm/Norm.cc b/src/orca-jedi/norm/Norm.cc
index 13f61f85..d6a2b65b 100644
--- a/src/orca-jedi/norm/Norm.cc
+++ b/src/orca-jedi/norm/Norm.cc
@@ -27,6 +27,7 @@ void Norm::applyInverse(Increment &) const {
 
 const double Norm::computeNorm(const Increment &) const {
   throw eckit::NotImplemented(Here());
+  return 0.0;
 }
 
 void Norm::print(std::ostream &) const {