cellml · agarny · Apr 14, 2026 · Apr 14, 2026 · Apr 27, 2026 · May 25, 2026
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
@@ -281,8 +281,8 @@ function(append_target_property _TARGET _PROPERTY _VALUE)
 endfunction()
 
 if(LIBCELLML_COVERAGE)
-  append_target_property(cellml COMPILE_FLAGS "-fprofile-arcs -ftest-coverage")
-  append_target_property(cellml LINK_FLAGS "-fprofile-arcs -ftest-coverage")
+  target_compile_options(cellml PRIVATE -fprofile-arcs -ftest-coverage)
+  target_link_options(cellml PUBLIC $<BUILD_INTERFACE:-fprofile-arcs>)
 
   # Share some paths with interested parties (tests)
   set(GCOV_ANALYSIS_PATH "${CMAKE_CURRENT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/cellml.dir" PARENT_SCOPE)
@@ -299,8 +299,8 @@ if(LIBCELLML_COVERAGE)
 endif()
 
 if(LIBCELLML_LLVM_COVERAGE)
-  append_target_property(cellml COMPILE_FLAGS "-fprofile-instr-generate -fcoverage-mapping")
-  append_target_property(cellml LINK_FLAGS "-fprofile-instr-generate")
+  target_compile_options(cellml PRIVATE -fprofile-instr-generate -fcoverage-mapping)
+  target_link_options(cellml PUBLIC $<BUILD_INTERFACE:-fprofile-instr-generate>)
 endif()
 
 install(TARGETS cellml EXPORT libcellml-targets

diff --git a/src/analyser.cpp b/src/analyser.cpp
diff --git a/src/analyser_p.h b/src/analyser_p.h
@@ -166,8 +166,8 @@ class Analyser::AnalyserImpl: public Logger::LoggerImpl
 
     GeneratorProfilePtr mGeneratorProfile = GeneratorProfile::create();
 
-    std::map<std::string, UnitsPtr> mStandardUnits;
-    std::map<AnalyserEquationAstPtr, UnitsPtr> mCiCnUnits;
+    std::unordered_map<std::string, UnitsPtr> mStandardUnits;
+    std::unordered_map<AnalyserEquationAstPtr, UnitsPtr> mCiCnUnits;
 
     AnalyserImpl();
 
@@ -183,10 +183,6 @@ class Analyser::AnalyserImpl: public Logger::LoggerImpl
     void analyseComponent(const ComponentPtr &component);
     void analyseComponentVariables(const ComponentPtr &component);
 
-    void equivalentVariables(const VariablePtr &variable,
-                             VariablePtrs &equivalentVariables) const;
-    VariablePtrs equivalentVariables(const VariablePtr &variable) const;
-
     void analyseEquationAst(const AnalyserEquationAstPtr &ast);
 
     void updateUnitsMapWithStandardUnit(const std::string &unitsName,
@@ -253,7 +249,7 @@ class Analyser::AnalyserImpl: public Logger::LoggerImpl
     static bool isExternalVariable(const AnalyserInternalVariablePtr &variable);
 
     bool isStateRateBased(const AnalyserEquationPtr &analyserEquation,
-                          AnalyserEquationPtrs &checkedEquations);
+                          std::unordered_set<AnalyserEquation *> &checkedEquations);
 
     void addInvalidVariableIssue(const AnalyserInternalVariablePtr &variable,
                                  Issue::ReferenceRule referenceRule);

diff --git a/src/analyserequation.cpp b/src/analyserequation.cpp
@@ -149,7 +149,7 @@ size_t AnalyserEquation::stateCount() const
     return mPimpl->mStates.size();
 }
 
-std::vector<AnalyserVariablePtr> AnalyserEquation::states() const
+const std::vector<AnalyserVariablePtr> &AnalyserEquation::states() const
 {
     return mPimpl->mStates;
 }
@@ -168,7 +168,7 @@ size_t AnalyserEquation::computedConstantCount() const
     return mPimpl->mComputedConstants.size();
 }
 
-std::vector<AnalyserVariablePtr> AnalyserEquation::computedConstants() const
+const std::vector<AnalyserVariablePtr> &AnalyserEquation::computedConstants() const
 {
     return mPimpl->mComputedConstants;
 }
@@ -187,7 +187,7 @@ size_t AnalyserEquation::algebraicVariableCount() const
     return mPimpl->mAlgebraicVariables.size();
 }
 
-std::vector<AnalyserVariablePtr> AnalyserEquation::algebraicVariables() const
+const std::vector<AnalyserVariablePtr> &AnalyserEquation::algebraicVariables() const
 {
     return mPimpl->mAlgebraicVariables;
 }
@@ -206,7 +206,7 @@ size_t AnalyserEquation::externalVariableCount() const
     return mPimpl->mExternalVariables.size();
 }
 
-std::vector<AnalyserVariablePtr> AnalyserEquation::externalVariables() const
+const std::vector<AnalyserVariablePtr> &AnalyserEquation::externalVariables() const
 {
     return mPimpl->mExternalVariables;
 }

diff --git a/src/analyserequationast.cpp b/src/analyserequationast.cpp
@@ -170,7 +170,7 @@ void AnalyserEquationAst::setType(Type type)
     mPimpl->mType = type;
 }
 
-std::string AnalyserEquationAst::value() const
+const std::string &AnalyserEquationAst::value() const
 {
     return mPimpl->mValue;
 }

diff --git a/src/analyserexternalvariable.cpp b/src/analyserexternalvariable.cpp
@@ -31,7 +31,7 @@ std::vector<VariablePtr>::iterator AnalyserExternalVariable::AnalyserExternalVar
                                                                                                           const std::string &componentName,
                                                                                                           const std::string &variableName)
 {
-    return std::find_if(mDependencies.begin(), mDependencies.end(), [=](const auto &v) {
+    return std::find_if(mDependencies.begin(), mDependencies.end(), [&](const auto &v) {
         return (owningModel(v) == model)
                && (owningComponent(v)->name() == componentName)
                && (v->name() == variableName);
@@ -40,7 +40,7 @@ std::vector<VariablePtr>::iterator AnalyserExternalVariable::AnalyserExternalVar
 
 std::vector<VariablePtr>::iterator AnalyserExternalVariable::AnalyserExternalVariableImpl::findDependency(const VariablePtr &variable)
 {
-    return std::find_if(mDependencies.begin(), mDependencies.end(), [=](const auto &v) {
+    return std::find_if(mDependencies.begin(), mDependencies.end(), [&](const auto &v) {
         return v == variable;
     });
 }
@@ -155,7 +155,7 @@ VariablePtr AnalyserExternalVariable::dependency(const ModelPtr &model,
                nullptr;
 }
 
-std::vector<VariablePtr> AnalyserExternalVariable::dependencies() const
+const std::vector<VariablePtr> &AnalyserExternalVariable::dependencies() const
 {
     return mPimpl->mDependencies;
 }

diff --git a/src/analysermodel.cpp b/src/analysermodel.cpp
@@ -157,10 +157,12 @@ size_t AnalyserModel::stateCount() const
     return mPimpl->mStates.size();
 }
 
-std::vector<AnalyserVariablePtr> AnalyserModel::states() const
+const std::vector<AnalyserVariablePtr> &AnalyserModel::states() const
 {
+    static const std::vector<AnalyserVariablePtr> NO_ANALYSER_VARIABLE;
+
     if (!isValid()) {
-        return {};
+        return NO_ANALYSER_VARIABLE;
     }
 
     return mPimpl->mStates;
@@ -185,10 +187,12 @@ size_t AnalyserModel::constantCount() const
     return mPimpl->mConstants.size();
 }
 
-std::vector<AnalyserVariablePtr> AnalyserModel::constants() const
+const std::vector<AnalyserVariablePtr> &AnalyserModel::constants() const
 {
+    static const std::vector<AnalyserVariablePtr> NO_ANALYSER_VARIABLE;
+
     if (!isValid()) {
-        return {};
+        return NO_ANALYSER_VARIABLE;
     }
 
     return mPimpl->mConstants;
@@ -212,10 +216,12 @@ size_t AnalyserModel::computedConstantCount() const
     return mPimpl->mComputedConstants.size();
 }
 
-std::vector<AnalyserVariablePtr> AnalyserModel::computedConstants() const
+const std::vector<AnalyserVariablePtr> &AnalyserModel::computedConstants() const
 {
+    static const std::vector<AnalyserVariablePtr> NO_ANALYSER_VARIABLE;
+
     if (!isValid()) {
-        return {};
+        return NO_ANALYSER_VARIABLE;
     }
 
     return mPimpl->mComputedConstants;
@@ -239,10 +245,12 @@ size_t AnalyserModel::algebraicVariableCount() const
     return mPimpl->mAlgebraicVariables.size();
 }
 
-std::vector<AnalyserVariablePtr> AnalyserModel::algebraicVariables() const
+const std::vector<AnalyserVariablePtr> &AnalyserModel::algebraicVariables() const
 {
+    static const std::vector<AnalyserVariablePtr> NO_ANALYSER_VARIABLE;
+
     if (!isValid()) {
-        return {};
+        return NO_ANALYSER_VARIABLE;
     }
 
     return mPimpl->mAlgebraicVariables;
@@ -266,10 +274,12 @@ size_t AnalyserModel::externalVariableCount() const
     return mPimpl->mExternalVariables.size();
 }
 
-std::vector<AnalyserVariablePtr> AnalyserModel::externalVariables() const
+const std::vector<AnalyserVariablePtr> &AnalyserModel::externalVariables() const
 {
+    static const std::vector<AnalyserVariablePtr> NO_ANALYSER_VARIABLE;
+
     if (!isValid()) {
-        return {};
+        return NO_ANALYSER_VARIABLE;
     }
 
     return mPimpl->mExternalVariables;
@@ -336,10 +346,12 @@ size_t AnalyserModel::analyserEquationCount() const
     return mPimpl->mAnalyserEquations.size();
 }
 
-std::vector<AnalyserEquationPtr> AnalyserModel::analyserEquations() const
+const std::vector<AnalyserEquationPtr> &AnalyserModel::analyserEquations() const
 {
+    static const std::vector<AnalyserEquationPtr> NO_ANALYSER_EQUATION;
+
     if (!isValid()) {
-        return {};
+        return NO_ANALYSER_EQUATION;
     }
 
     return mPimpl->mAnalyserEquations;

diff --git a/src/annotator.cpp b/src/annotator.cpp
@@ -17,6 +17,7 @@ limitations under the License.
 #include "libcellml/annotator.h"
 
 #include <algorithm>
+#include <format>
 #include <sstream>
 #include <unordered_map>
 
@@ -236,13 +237,17 @@ void Annotator::AnnotatorImpl::listComponentIdsAndItems(const ComponentPtr &comp
                 if (idList.count(id) != 0) {
                     // Get the range of items with this identifier:
                     auto rangePair = idList.equal_range(id);
+                    auto compVar = owningComponent(variable);
+                    auto compEquivVar = owningComponent(equivalentVariable);
                     for (auto it = rangePair.first; it != rangePair.second; ++it) {
                         // Make sure it's also a CONNECTION item.
                         if (it->second->type() == CellmlElementType::CONNECTION) {
                             auto testPair = it->second->variablePair();
-                            if ((owningComponent(testPair->variable1()) == owningComponent(equivalentVariable)) && (owningComponent(testPair->variable2()) == owningComponent(variable))) {
-                                found = true;
-                            } else if ((owningComponent(testPair->variable2()) == owningComponent(equivalentVariable)) && (owningComponent(testPair->variable1()) == owningComponent(variable))) {
+                            auto compVar1 = owningComponent(testPair->variable1());
+                            auto compVar2 = owningComponent(testPair->variable2());
+
+                            if (((compVar1 == compEquivVar) && (compVar2 == compVar))
+                                || ((compVar2 == compEquivVar) && (compVar1 == compVar))) {
                                 found = true;
                             }
                         }
@@ -352,7 +357,7 @@ AnyCellmlElementPtr Annotator::AnnotatorImpl::convertToWeak(const AnyCellmlEleme
 
     converted->mPimpl->mType = type;
 
-    switch (item->type()) {
+    switch (type) {
     case CellmlElementType::COMPONENT:
     case CellmlElementType::COMPONENT_REF: {
         ComponentWeakPtr weakComponent = item->component();
@@ -517,7 +522,7 @@ void Annotator::AnnotatorImpl::addIssueInvalidArgument(CellmlElementType type)
 void Annotator::AnnotatorImpl::addIssueNonUnique(const std::string &id)
 {
     auto issue = Issue::IssueImpl::create();
-    issue->mPimpl->setDescription("The identifier '" + id + "' occurs " + std::to_string(mIdList.count(id)) + " times in the model so a unique item cannot be located.");
+    issue->mPimpl->setDescription("The identifier '" + id + "' occurs " + std::format("{}", mIdList.count(id)) + " times in the model so a unique item cannot be located.");
     issue->mPimpl->setLevel(Issue::Level::WARNING);
     issue->mPimpl->setReferenceRule(Issue::ReferenceRule::ANNOTATOR_ID_NOT_UNIQUE);
     addIssue(issue);
@@ -1417,20 +1422,24 @@ size_t Annotator::itemCount(const std::string &id)
 
 void Annotator::AnnotatorImpl::doUpdateComponentHash(const ComponentPtr &component, std::string &idsString)
 {
-    for (size_t i = 0; i < component->variableCount(); ++i) {
-        idsString += "v=" + std::to_string(i) + component->variable(i)->id();
+    const auto variableCount = component->variableCount();
+    const auto resetCount = component->resetCount();
+    const auto componentCount = component->componentCount();
+
+    for (size_t i = 0; i < variableCount; ++i) {
+        idsString += "v=" + std::format("{}", i) + component->variable(i)->id();
     }
 
-    for (size_t i = 0; i < component->resetCount(); ++i) {
+    for (size_t i = 0; i < resetCount; ++i) {
         auto reset = component->reset(i);
-        idsString += "r=" + std::to_string(i) + reset->id() + "rv=" + reset->resetValueId() + "tv=" + reset->testValueId();
+        idsString += "r=" + std::format("{}", i) + reset->id() + "rv=" + reset->resetValueId() + "tv=" + reset->testValueId();
     }
 
     // Note that MathML identifiers are not yet included.
 
-    for (size_t i = 0; i < component->componentCount(); ++i) {
+    for (size_t i = 0; i < componentCount; ++i) {
         auto child = component->component(i);
-        idsString += "c=" + std::to_string(i) + child->id() + "ce=" + child->encapsulationId();
+        idsString += "c=" + std::format("{}", i) + child->id() + "ce=" + child->encapsulationId();
         doUpdateComponentHash(child, idsString);
     }
 }
@@ -1448,21 +1457,21 @@ size_t Annotator::AnnotatorImpl::generateHash()
         auto importSources = getAllImportSources(model);
         i = 0;
         for (auto &importSource : importSources) {
-            idsString += "i=" + std::to_string(++i) + importSource->id();
+            idsString += "i=" + std::format("{}", ++i) + importSource->id();
         }
 
         for (i = 0; i < model->unitsCount(); ++i) {
             auto units = model->units(i);
-            idsString += "U=" + std::to_string(i) + units->id();
+            idsString += "U=" + std::format("{}", i) + units->id();
             for (size_t j = 0; j < units->unitCount(); ++j) {
-                idsString += "u=" + std::to_string(j) + units->unitId(j);
+                idsString += "u=" + std::format("{}", j) + units->unitId(j);
             }
         }
 
         for (i = 0; i < model->componentCount(); ++i) {
             auto component = model->component(i);
-            idsString += "c=" + std::to_string(i) + component->id();
-            idsString += "cr=" + std::to_string(i) + component->encapsulationId();
+            idsString += "c=" + std::format("{}", i) + component->id();
+            idsString += "cr=" + std::format("{}", i) + component->encapsulationId();
             doUpdateComponentHash(component, idsString);
         }
 

diff --git a/src/api/libcellml/analyserequation.h b/src/api/libcellml/analyserequation.h
@@ -185,7 +185,7 @@ class LIBCELLML_EXPORT AnalyserEquation
      *
      * @return The states as a @c std::vector.
      */
-    std::vector<AnalyserVariablePtr> states() const;
+    const std::vector<AnalyserVariablePtr> &states() const;
 
     /**
      * @brief Get the state, at @p index, computed by this @ref AnalyserEquation.
@@ -214,7 +214,7 @@ class LIBCELLML_EXPORT AnalyserEquation
      *
      * @return The computed constants as a @c std::vector.
      */
-    std::vector<AnalyserVariablePtr> computedConstants() const;
+    const std::vector<AnalyserVariablePtr> &computedConstants() const;
 
     /**
      * @brief Get the computed constant, at @p index, computed by this @ref AnalyserEquation.
@@ -243,7 +243,7 @@ class LIBCELLML_EXPORT AnalyserEquation
      *
      * @return The algebraic variables as a @c std::vector.
      */
-    std::vector<AnalyserVariablePtr> algebraicVariables() const;
+    const std::vector<AnalyserVariablePtr> &algebraicVariables() const;
 
     /**
      * @brief Get the algebraic variable, at @p index, computed by this @ref AnalyserEquation.
@@ -272,7 +272,7 @@ class LIBCELLML_EXPORT AnalyserEquation
      *
      * @return The external variables as a @c std::vector.
      */
-    std::vector<AnalyserVariablePtr> externalVariables() const;
+    const std::vector<AnalyserVariablePtr> &externalVariables() const;
 
     /**
      * @brief Get the external variable, at @p index, computed by this @ref AnalyserEquation.

diff --git a/src/api/libcellml/analyserequationast.h b/src/api/libcellml/analyserequationast.h
@@ -190,7 +190,7 @@ class LIBCELLML_EXPORT AnalyserEquationAst
      *
      * @return The value.
      */
-    std::string value() const;
+    const std::string &value() const;
 
     /**
      * @brief Set the value for this @ref AnalyserEquationAst.

diff --git a/src/api/libcellml/analyserexternalvariable.h b/src/api/libcellml/analyserexternalvariable.h
@@ -227,7 +227,7 @@ class LIBCELLML_EXPORT AnalyserExternalVariable
      *
      * @return The dependencies as a @c std::vector.
      */
-    std::vector<VariablePtr> dependencies() const;
+    const std::vector<VariablePtr> &dependencies() const;
 
     /**
      * @brief Get the number of dependencies of this @ref AnalyserExternalVariable.