From d0d5434a9a848fe5da2af20452deb2cb1c471b1a Mon Sep 17 00:00:00 2001
From: Clemens Schmid <clemisch@tuta.io>
Date: Mon, 2 Feb 2026 14:49:16 +0100
Subject: [PATCH 1/3] expose lsq.GetVarianceCovarianceMap()

---
 src/extensions/lsq_ext.cpp | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/extensions/lsq_ext.cpp b/src/extensions/lsq_ext.cpp
index b63d1044..116d5e67 100644
--- a/src/extensions/lsq_ext.cpp
+++ b/src/extensions/lsq_ext.cpp
@@ -19,6 +19,8 @@
 
 #include <boost/python/class.hpp>
 #include <boost/python/copy_const_reference.hpp>
+#include <boost/python/dict.hpp>
+#include <boost/python/tuple.hpp>
 
 #include <string>
 
@@ -45,6 +47,22 @@ bool _SafeRefine(LSQNumObj & lsq, REAL maxChi2factor, int nbCycle, bool useLeven
                           callBeginEndOptimization, minChi2var);
 }
 
+bp::dict _GetVarianceCovarianceMap(LSQNumObj & lsq)
+{
+    const std::map<std::pair<const RefinablePar*, const RefinablePar*>, REAL> &m =
+        lsq.GetVarianceCovarianceMap();
+    bp::dict d;
+    for (std::map<std::pair<const RefinablePar*, const RefinablePar*>, REAL>::const_iterator it = m.begin();
+         it != m.end(); ++it)
+    {
+        const RefinablePar *pi = it->first.first;
+        const RefinablePar *pj = it->first.second;
+        d[bp::make_tuple(bp::ptr(const_cast<RefinablePar*>(pi)),
+                         bp::ptr(const_cast<RefinablePar*>(pj)))] = it->second;
+    }
+    return d;
+}
+
 }   // namespace
 
 void wrap_lsq()
@@ -102,6 +120,7 @@ void wrap_lsq()
         .def("GetLSQDeriv", &LSQNumObj::GetLSQDeriv,
                 bp::arg("par"),
                 return_value_policy<copy_const_reference>())
+        .def("GetVarianceCovarianceMap", &_GetVarianceCovarianceMap)
         .def("BeginOptimization", &LSQNumObj::BeginOptimization,
                 (bp::arg("allowApproximations")=false,
                  bp::arg("enableRestraints")=false))

From e52f3c97681faeae30ce3e3b70e06780b0859c3e Mon Sep 17 00:00:00 2001
From: Clemens Schmid <clemisch@tuta.io>
Date: Mon, 2 Feb 2026 15:49:28 +0100
Subject: [PATCH 2/3] change keys of cov matrix to param names instead of param
 pointers

---
 src/extensions/lsq_ext.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/extensions/lsq_ext.cpp b/src/extensions/lsq_ext.cpp
index 116d5e67..b28ba8d0 100644
--- a/src/extensions/lsq_ext.cpp
+++ b/src/extensions/lsq_ext.cpp
@@ -57,8 +57,7 @@ bp::dict _GetVarianceCovarianceMap(LSQNumObj & lsq)
     {
         const RefinablePar *pi = it->first.first;
         const RefinablePar *pj = it->first.second;
-        d[bp::make_tuple(bp::ptr(const_cast<RefinablePar*>(pi)),
-                         bp::ptr(const_cast<RefinablePar*>(pj)))] = it->second;
+        d[bp::make_tuple(pi->GetName(), pj->GetName())] = it->second;
     }
     return d;
 }

From 65f5c0323f7ae4c8deb546222902d2a1585ce9e7 Mon Sep 17 00:00:00 2001
From: Clemens Schmid <clem.schmid@gmail.com>
Date: Tue, 25 Aug 2026 14:17:04 +0200
Subject: [PATCH 3/3] add news file

---
 news/get_variance_covariance_map.rst | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 news/get_variance_covariance_map.rst

diff --git a/news/get_variance_covariance_map.rst b/news/get_variance_covariance_map.rst
new file mode 100644
index 00000000..5e9db10f
--- /dev/null
+++ b/news/get_variance_covariance_map.rst
@@ -0,0 +1,23 @@
+**Added:**
+
+* Expose ``lsq.GetVarianceCovarianceMap()`` for covariance between refined parameters
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>