diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a2747fa..2ed722c8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,12 +52,12 @@ file(GLOB UNO_SOURCE_FILES
    uno/ingredients/inequality_handling_methods/*.cpp
    uno/ingredients/inequality_handling_methods/inequality_constrained_methods/*.cpp
    uno/ingredients/inequality_handling_methods/interior_point_methods/*.cpp
+   uno/ingredients/subproblems/*.cpp
    uno/model/*.cpp
    uno/optimization/*.cpp
    uno/options/*.cpp
    uno/preprocessing/*.cpp
-   uno/reformulation/*.cpp
-   uno/solvers/*.cpp
+        uno/ingredients/subproblem_solvers/*.cpp
    uno/tools/*.cpp
 )
 
@@ -115,14 +115,14 @@ else()
    endif()
 endif()
 if(HSL OR MA57)
-   list(APPEND UNO_SOURCE_FILES uno/solvers/MA57/MA57Solver.cpp)
+   list(APPEND UNO_SOURCE_FILES uno/ingredients/subproblem_solvers/MA57/MA57Solver.cpp)
    list(APPEND TESTS_UNO_SOURCE_FILES unotest/functional_tests/MA57SolverTests.cpp)
    
    find_package(BLAS REQUIRED)
    list(APPEND LIBRARIES ${BLAS_LIBRARIES})
 endif()
 if(HSL OR MA27)
-   list(APPEND UNO_SOURCE_FILES uno/solvers/MA27/MA27Solver.cpp)
+   list(APPEND UNO_SOURCE_FILES uno/ingredients/subproblem_solvers/MA27/MA27Solver.cpp)
    list(APPEND TESTS_UNO_SOURCE_FILES unotest/functional_tests/MA27SolverTests.cpp)
 
    find_package(BLAS REQUIRED)
@@ -142,7 +142,7 @@ find_library(BQPD bqpd)
 if(NOT BQPD)
    message(WARNING "Optional library BQPD was not found.")
 else()
-   list(APPEND UNO_SOURCE_FILES uno/solvers/BQPD/BQPDSolver.cpp uno/solvers/BQPD/wdotd.f)
+   list(APPEND UNO_SOURCE_FILES uno/ingredients/subproblem_solvers/BQPD/BQPDSolver.cpp uno/ingredients/subproblem_solvers/BQPD/wdotd.f)
    list(APPEND TESTS_UNO_SOURCE_FILES unotest/functional_tests/BQPDSolverTests.cpp)
    link_to_uno(bqpd ${BQPD})
 endif()
@@ -152,7 +152,7 @@ find_package(HIGHS)
 if(NOT HIGHS)
    message(WARNING "Optional library HiGHS was not found.")
 else()
-   list(APPEND UNO_SOURCE_FILES uno/solvers/HiGHS/HiGHSSolver.cpp)
+   list(APPEND UNO_SOURCE_FILES uno/ingredients/subproblem_solvers/HiGHS/HiGHSSolver.cpp)
    list(APPEND TESTS_UNO_SOURCE_FILES unotest/functional_tests/HiGHSSolverTests.cpp)
    link_to_uno(highs ${HIGHS})
    list(APPEND LIBRARIES highs::highs)
@@ -163,7 +163,7 @@ find_package(MUMPS)
 if(NOT MUMPS_LIBRARY)
    message(WARNING "Optional library MUMPS was not found.")
 else()
-   list(APPEND UNO_SOURCE_FILES uno/solvers/MUMPS/MUMPSSolver.cpp)
+   list(APPEND UNO_SOURCE_FILES uno/ingredients/subproblem_solvers/MUMPS/MUMPSSolver.cpp)
    list(APPEND TESTS_UNO_SOURCE_FILES unotest/functional_tests/MUMPSSolverTests.cpp)
    list(APPEND LIBRARIES ${MUMPS_LIBRARY} ${MUMPS_COMMON_LIBRARY} ${MUMPS_PORD_LIBRARY})
    
diff --git a/uno/Uno.cpp b/uno/Uno.cpp
index c4af1081..db683db0 100644
--- a/uno/Uno.cpp
+++ b/uno/Uno.cpp
@@ -8,13 +8,13 @@
 #include "ingredients/globalization_mechanisms/GlobalizationMechanismFactory.hpp"
 #include "ingredients/globalization_strategies/GlobalizationStrategyFactory.hpp"
 #include "ingredients/inequality_handling_methods/InequalityHandlingMethodFactory.hpp"
+#include "ingredients/subproblem_solvers/QPSolverFactory.hpp"
+#include "ingredients/subproblem_solvers/LPSolverFactory.hpp"
+#include "ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
 #include "linear_algebra/Vector.hpp"
 #include "model/Model.hpp"
 #include "optimization/Iterate.hpp"
 #include "optimization/WarmstartInformation.hpp"
-#include "solvers/QPSolverFactory.hpp"
-#include "solvers/LPSolverFactory.hpp"
-#include "solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
 #include "tools/Logger.hpp"
 #include "optimization/OptimizationStatus.hpp"
 #include "options/Options.hpp"
diff --git a/uno/ingredients/constraint_relaxation_strategies/ConstraintRelaxationStrategy.cpp b/uno/ingredients/constraint_relaxation_strategies/ConstraintRelaxationStrategy.cpp
index 5c91485e..28f042de 100644
--- a/uno/ingredients/constraint_relaxation_strategies/ConstraintRelaxationStrategy.cpp
+++ b/uno/ingredients/constraint_relaxation_strategies/ConstraintRelaxationStrategy.cpp
@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project directory for details.
 
 #include "ConstraintRelaxationStrategy.hpp"
+#include "OptimizationProblem.hpp"
 #include "ingredients/globalization_strategies/GlobalizationStrategy.hpp"
 #include "ingredients/globalization_strategies/GlobalizationStrategyFactory.hpp"
 #include "optimization/Direction.hpp"
@@ -11,7 +12,6 @@
 #include "model/Model.hpp"
 #include "optimization/Iterate.hpp"
 #include "optimization/Multipliers.hpp"
-#include "reformulation/OptimizationProblem.hpp"
 #include "symbolic/VectorView.hpp"
 #include "symbolic/Expression.hpp"
 #include "options/Options.hpp"
diff --git a/uno/reformulation/ElasticVariables.cpp b/uno/ingredients/constraint_relaxation_strategies/ElasticVariables.cpp
similarity index 100%
rename from uno/reformulation/ElasticVariables.cpp
rename to uno/ingredients/constraint_relaxation_strategies/ElasticVariables.cpp
diff --git a/uno/reformulation/ElasticVariables.hpp b/uno/ingredients/constraint_relaxation_strategies/ElasticVariables.hpp
similarity index 96%
rename from uno/reformulation/ElasticVariables.hpp
rename to uno/ingredients/constraint_relaxation_strategies/ElasticVariables.hpp
index 7c1c7c15..cc83765b 100644
--- a/uno/reformulation/ElasticVariables.hpp
+++ b/uno/ingredients/constraint_relaxation_strategies/ElasticVariables.hpp
@@ -30,4 +30,4 @@ namespace uno {
    };
 } // namespace
 
-#endif // UNO_ELASTICVARIABLES_H
+#endif // UNO_ELASTICVARIABLES_H
\ No newline at end of file
diff --git a/uno/ingredients/constraint_relaxation_strategies/FeasibilityRestoration.hpp b/uno/ingredients/constraint_relaxation_strategies/FeasibilityRestoration.hpp
index 26810bc3..f71f4fab 100644
--- a/uno/ingredients/constraint_relaxation_strategies/FeasibilityRestoration.hpp
+++ b/uno/ingredients/constraint_relaxation_strategies/FeasibilityRestoration.hpp
@@ -7,8 +7,8 @@
 #include <memory>
 #include "ConstraintRelaxationStrategy.hpp"
 #include "ingredients/globalization_strategies/ProgressMeasures.hpp"
-#include "reformulation/OptimalityProblem.hpp"
-#include "reformulation/l1RelaxedProblem.hpp"
+#include "OptimalityProblem.hpp"
+#include "l1RelaxedProblem.hpp"
 
 namespace uno {
    enum class Phase {FEASIBILITY_RESTORATION = 1, OPTIMALITY = 2};
diff --git a/uno/reformulation/OptimalityProblem.cpp b/uno/ingredients/constraint_relaxation_strategies/OptimalityProblem.cpp
similarity index 100%
rename from uno/reformulation/OptimalityProblem.cpp
rename to uno/ingredients/constraint_relaxation_strategies/OptimalityProblem.cpp
diff --git a/uno/reformulation/OptimalityProblem.hpp b/uno/ingredients/constraint_relaxation_strategies/OptimalityProblem.hpp
similarity index 98%
rename from uno/reformulation/OptimalityProblem.hpp
rename to uno/ingredients/constraint_relaxation_strategies/OptimalityProblem.hpp
index 9f488dae..ba374d3a 100644
--- a/uno/reformulation/OptimalityProblem.hpp
+++ b/uno/ingredients/constraint_relaxation_strategies/OptimalityProblem.hpp
@@ -37,4 +37,4 @@ namespace uno {
    };
 } // namespace
 
-#endif // UNO_OPTIMALITYPROBLEM_H
+#endif // UNO_OPTIMALITYPROBLEM_H
\ No newline at end of file
diff --git a/uno/reformulation/OptimizationProblem.cpp b/uno/ingredients/constraint_relaxation_strategies/OptimizationProblem.cpp
similarity index 100%
rename from uno/reformulation/OptimizationProblem.cpp
rename to uno/ingredients/constraint_relaxation_strategies/OptimizationProblem.cpp
diff --git a/uno/reformulation/OptimizationProblem.hpp b/uno/ingredients/constraint_relaxation_strategies/OptimizationProblem.hpp
similarity index 100%
rename from uno/reformulation/OptimizationProblem.hpp
rename to uno/ingredients/constraint_relaxation_strategies/OptimizationProblem.hpp
diff --git a/uno/ingredients/constraint_relaxation_strategies/l1Relaxation.hpp b/uno/ingredients/constraint_relaxation_strategies/l1Relaxation.hpp
index e3635d0c..387b9ddc 100644
--- a/uno/ingredients/constraint_relaxation_strategies/l1Relaxation.hpp
+++ b/uno/ingredients/constraint_relaxation_strategies/l1Relaxation.hpp
@@ -8,7 +8,7 @@
 #include "ConstraintRelaxationStrategy.hpp"
 #include "ingredients/globalization_strategies/ProgressMeasures.hpp"
 #include "optimization/Multipliers.hpp"
-#include "reformulation/l1RelaxedProblem.hpp"
+#include "l1RelaxedProblem.hpp"
 
 namespace uno {
    struct l1RelaxationParameters {
diff --git a/uno/reformulation/l1RelaxedProblem.cpp b/uno/ingredients/constraint_relaxation_strategies/l1RelaxedProblem.cpp
similarity index 100%
rename from uno/reformulation/l1RelaxedProblem.cpp
rename to uno/ingredients/constraint_relaxation_strategies/l1RelaxedProblem.cpp
diff --git a/uno/reformulation/l1RelaxedProblem.hpp b/uno/ingredients/constraint_relaxation_strategies/l1RelaxedProblem.hpp
similarity index 100%
rename from uno/reformulation/l1RelaxedProblem.hpp
rename to uno/ingredients/constraint_relaxation_strategies/l1RelaxedProblem.hpp
diff --git a/uno/ingredients/hessian_models/ConvexifiedHessian.cpp b/uno/ingredients/hessian_models/ConvexifiedHessian.cpp
index fe5a532d..a508f80f 100644
--- a/uno/ingredients/hessian_models/ConvexifiedHessian.cpp
+++ b/uno/ingredients/hessian_models/ConvexifiedHessian.cpp
@@ -4,12 +4,11 @@
 #include <stdexcept>
 #include "ConvexifiedHessian.hpp"
 #include "ingredients/hessian_models/UnstableRegularization.hpp"
-#include "reformulation/OptimizationProblem.hpp"
-#include "solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
-#include "solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
+#include "ingredients/constraint_relaxation_strategies/OptimizationProblem.hpp"
+#include "ingredients/subproblem_solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
+#include "ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
 #include "tools/Logger.hpp"
 #include "options/Options.hpp"
-#include "tools/Infinity.hpp"
 #include "tools/Statistics.hpp"
 
 namespace uno {
diff --git a/uno/ingredients/hessian_models/ExactHessian.cpp b/uno/ingredients/hessian_models/ExactHessian.cpp
index 16886885..6299c2e4 100644
--- a/uno/ingredients/hessian_models/ExactHessian.cpp
+++ b/uno/ingredients/hessian_models/ExactHessian.cpp
@@ -2,7 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project directory for details.
 
 #include "ExactHessian.hpp"
-#include "reformulation/OptimizationProblem.hpp"
+#include "ingredients/constraint_relaxation_strategies/OptimizationProblem.hpp"
 #include "options/Options.hpp"
 
 namespace uno {
diff --git a/uno/ingredients/hessian_models/HessianModelFactory.cpp b/uno/ingredients/hessian_models/HessianModelFactory.cpp
index a7ee8cde..f679b6fa 100644
--- a/uno/ingredients/hessian_models/HessianModelFactory.cpp
+++ b/uno/ingredients/hessian_models/HessianModelFactory.cpp
@@ -6,7 +6,7 @@
 #include "ConvexifiedHessian.hpp"
 #include "ExactHessian.hpp"
 #include "ZeroHessian.hpp"
-#include "solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
+#include "ingredients/subproblem_solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
 
 namespace uno {
    std::unique_ptr<HessianModel> HessianModelFactory::create(const std::string& hessian_model, size_t dimension, size_t maximum_number_nonzeros,
diff --git a/uno/ingredients/hessian_models/ZeroHessian.cpp b/uno/ingredients/hessian_models/ZeroHessian.cpp
index ab4e80ae..63522a3e 100644
--- a/uno/ingredients/hessian_models/ZeroHessian.cpp
+++ b/uno/ingredients/hessian_models/ZeroHessian.cpp
@@ -2,7 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project directory for details.
 
 #include "ZeroHessian.hpp"
-#include "reformulation/OptimizationProblem.hpp"
+#include "ingredients/constraint_relaxation_strategies/OptimizationProblem.hpp"
 #include "options/Options.hpp"
 
 namespace uno {
diff --git a/uno/ingredients/inequality_handling_methods/InequalityHandlingMethodFactory.cpp b/uno/ingredients/inequality_handling_methods/InequalityHandlingMethodFactory.cpp
index 727955bb..90adc019 100644
--- a/uno/ingredients/inequality_handling_methods/InequalityHandlingMethodFactory.cpp
+++ b/uno/ingredients/inequality_handling_methods/InequalityHandlingMethodFactory.cpp
@@ -7,8 +7,8 @@
 #include "inequality_constrained_methods/QPSubproblem.hpp"
 #include "inequality_constrained_methods/LPSubproblem.hpp"
 #include "interior_point_methods/PrimalDualInteriorPointMethod.hpp"
-#include "solvers/QPSolverFactory.hpp"
-#include "solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
+#include "ingredients/subproblem_solvers/QPSolverFactory.hpp"
+#include "ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
 #include "options/Options.hpp"
 
 namespace uno {
diff --git a/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/InequalityConstrainedMethod.cpp b/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/InequalityConstrainedMethod.cpp
index f0cab785..1c0127ca 100644
--- a/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/InequalityConstrainedMethod.cpp
+++ b/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/InequalityConstrainedMethod.cpp
@@ -5,7 +5,7 @@
 #include "optimization/Direction.hpp"
 #include "optimization/Iterate.hpp"
 #include "linear_algebra/Vector.hpp"
-#include "reformulation/l1RelaxedProblem.hpp"
+#include "ingredients/constraint_relaxation_strategies/l1RelaxedProblem.hpp"
 #include "options/Options.hpp"
 #include "symbolic/VectorView.hpp"
 
diff --git a/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/LPSubproblem.cpp b/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/LPSubproblem.cpp
index 7d3c9298..1eb691c7 100644
--- a/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/LPSubproblem.cpp
+++ b/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/LPSubproblem.cpp
@@ -4,9 +4,9 @@
 #include "LPSubproblem.hpp"
 #include "optimization/Direction.hpp"
 #include "optimization/WarmstartInformation.hpp"
-#include "reformulation/OptimizationProblem.hpp"
-#include "solvers/LPSolver.hpp"
-#include "solvers/LPSolverFactory.hpp"
+#include "ingredients/constraint_relaxation_strategies/OptimizationProblem.hpp"
+#include "ingredients/subproblem_solvers/LPSolver.hpp"
+#include "ingredients/subproblem_solvers/LPSolverFactory.hpp"
 #include "options/Options.hpp"
 
 namespace uno {
diff --git a/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/QPSubproblem.cpp b/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/QPSubproblem.cpp
index fdba8a54..812070c8 100644
--- a/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/QPSubproblem.cpp
+++ b/uno/ingredients/inequality_handling_methods/inequality_constrained_methods/QPSubproblem.cpp
@@ -3,15 +3,13 @@
 
 #include "QPSubproblem.hpp"
 #include "optimization/Direction.hpp"
-#include "ingredients/hessian_models/HessianModelFactory.hpp"
-#include "linear_algebra/SymmetricMatrix.hpp"
 #include "optimization/Iterate.hpp"
 #include "optimization/WarmstartInformation.hpp"
 #include "preprocessing/Preprocessing.hpp"
-#include "reformulation/OptimizationProblem.hpp"
-#include "solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
-#include "solvers/QPSolver.hpp"
-#include "solvers/QPSolverFactory.hpp"
+#include "ingredients/constraint_relaxation_strategies/OptimizationProblem.hpp"
+#include "ingredients/subproblem_solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
+#include "ingredients/subproblem_solvers/QPSolver.hpp"
+#include "ingredients/subproblem_solvers/QPSolverFactory.hpp"
 #include "options/Options.hpp"
 #include "tools/Statistics.hpp"
 
diff --git a/uno/ingredients/inequality_handling_methods/interior_point_methods/BarrierParameterUpdateStrategy.cpp b/uno/ingredients/inequality_handling_methods/interior_point_methods/BarrierParameterUpdateStrategy.cpp
index 7cb67a6d..74d14b84 100644
--- a/uno/ingredients/inequality_handling_methods/interior_point_methods/BarrierParameterUpdateStrategy.cpp
+++ b/uno/ingredients/inequality_handling_methods/interior_point_methods/BarrierParameterUpdateStrategy.cpp
@@ -5,7 +5,7 @@
 #include <cmath>
 #include "BarrierParameterUpdateStrategy.hpp"
 #include "optimization/Iterate.hpp"
-#include "reformulation/OptimizationProblem.hpp"
+#include "ingredients/constraint_relaxation_strategies/OptimizationProblem.hpp"
 #include "symbolic/VectorExpression.hpp"
 #include "tools/Logger.hpp"
 #include "options/Options.hpp"
diff --git a/uno/ingredients/inequality_handling_methods/interior_point_methods/PrimalDualInteriorPointMethod.cpp b/uno/ingredients/inequality_handling_methods/interior_point_methods/PrimalDualInteriorPointMethod.cpp
index 1fbddff7..63aefb2c 100644
--- a/uno/ingredients/inequality_handling_methods/interior_point_methods/PrimalDualInteriorPointMethod.cpp
+++ b/uno/ingredients/inequality_handling_methods/interior_point_methods/PrimalDualInteriorPointMethod.cpp
@@ -4,15 +4,14 @@
 #include <cmath>
 #include "PrimalDualInteriorPointMethod.hpp"
 #include "PrimalDualInteriorPointProblem.hpp"
+#include "ingredients/constraint_relaxation_strategies/l1RelaxedProblem.hpp"
+#include "ingredients/subproblem_solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
+#include "ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
+#include "linear_algebra/SparseStorageFactory.hpp"
 #include "optimization/Direction.hpp"
 #include "optimization/Iterate.hpp"
-#include "ingredients/hessian_models/HessianModelFactory.hpp"
-#include "linear_algebra/SparseStorageFactory.hpp"
-#include "solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
-#include "solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
 #include "optimization/WarmstartInformation.hpp"
 #include "preprocessing/Preprocessing.hpp"
-#include "reformulation/l1RelaxedProblem.hpp"
 #include "symbolic/VectorView.hpp"
 #include "tools/Infinity.hpp"
 
@@ -187,7 +186,7 @@ namespace uno {
 
       // check the inertia
       [[maybe_unused]] auto [number_pos_eigenvalues, number_neg_eigenvalues, number_zero_eigenvalues] = this->linear_solver->get_inertia();
-      assert(number_pos_eigenvalues == problem.number_variables && number_neg_eigenvalues == problem.number_constraints && number_zero_eigenvalues == 0);
+      assert(number_pos_eigenvalues == number_variables && number_neg_eigenvalues == number_constraints && number_zero_eigenvalues == 0);
 
       // rhs
       this->assemble_augmented_rhs(current_multipliers, number_variables, number_constraints);
diff --git a/uno/ingredients/inequality_handling_methods/interior_point_methods/PrimalDualInteriorPointProblem.hpp b/uno/ingredients/inequality_handling_methods/interior_point_methods/PrimalDualInteriorPointProblem.hpp
index 6416f952..d909a6a6 100644
--- a/uno/ingredients/inequality_handling_methods/interior_point_methods/PrimalDualInteriorPointProblem.hpp
+++ b/uno/ingredients/inequality_handling_methods/interior_point_methods/PrimalDualInteriorPointProblem.hpp
@@ -4,7 +4,7 @@
 #ifndef UNO_PRIMALDUALINTERIORPOINTPROBLEM_H
 #define UNO_PRIMALDUALINTERIORPOINTPROBLEM_H
 
-#include "reformulation/OptimizationProblem.hpp"
+#include "ingredients/constraint_relaxation_strategies/OptimizationProblem.hpp"
 
 namespace uno {
    class PrimalDualInteriorPointProblem : public OptimizationProblem {
diff --git a/uno/solvers/BQPD/BQPDSolver.cpp b/uno/ingredients/subproblem_solvers/BQPD/BQPDSolver.cpp
similarity index 100%
rename from uno/solvers/BQPD/BQPDSolver.cpp
rename to uno/ingredients/subproblem_solvers/BQPD/BQPDSolver.cpp
diff --git a/uno/solvers/BQPD/BQPDSolver.hpp b/uno/ingredients/subproblem_solvers/BQPD/BQPDSolver.hpp
similarity index 98%
rename from uno/solvers/BQPD/BQPDSolver.hpp
rename to uno/ingredients/subproblem_solvers/BQPD/BQPDSolver.hpp
index 0304f517..87cf064e 100644
--- a/uno/solvers/BQPD/BQPDSolver.hpp
+++ b/uno/ingredients/subproblem_solvers/BQPD/BQPDSolver.hpp
@@ -8,7 +8,7 @@
 #include <vector>
 #include "ingredients/subproblems/SubproblemStatus.hpp"
 #include "linear_algebra/Vector.hpp"
-#include "solvers/QPSolver.hpp"
+#include "ingredients/subproblem_solvers/QPSolver.hpp"
 
 namespace uno {
    // forward declaration
diff --git a/uno/solvers/BQPD/wdotd.f b/uno/ingredients/subproblem_solvers/BQPD/wdotd.f
similarity index 100%
rename from uno/solvers/BQPD/wdotd.f
rename to uno/ingredients/subproblem_solvers/BQPD/wdotd.f
diff --git a/uno/solvers/DirectSymmetricIndefiniteLinearSolver.hpp b/uno/ingredients/subproblem_solvers/DirectSymmetricIndefiniteLinearSolver.hpp
similarity index 95%
rename from uno/solvers/DirectSymmetricIndefiniteLinearSolver.hpp
rename to uno/ingredients/subproblem_solvers/DirectSymmetricIndefiniteLinearSolver.hpp
index df5ed7c9..e08d449f 100644
--- a/uno/solvers/DirectSymmetricIndefiniteLinearSolver.hpp
+++ b/uno/ingredients/subproblem_solvers/DirectSymmetricIndefiniteLinearSolver.hpp
@@ -4,7 +4,7 @@
 #ifndef UNO_DIRECTSYMMETRICINDEFINITELINEARSOLVER_H
 #define UNO_DIRECTSYMMETRICINDEFINITELINEARSOLVER_H
 
-#include "solvers/SymmetricIndefiniteLinearSolver.hpp"
+#include "SymmetricIndefiniteLinearSolver.hpp"
 
 namespace uno {
    template <typename IndexType, typename ElementType>
diff --git a/uno/solvers/HiGHS/HiGHSSolver.cpp b/uno/ingredients/subproblem_solvers/HiGHS/HiGHSSolver.cpp
similarity index 100%
rename from uno/solvers/HiGHS/HiGHSSolver.cpp
rename to uno/ingredients/subproblem_solvers/HiGHS/HiGHSSolver.cpp
diff --git a/uno/solvers/HiGHS/HiGHSSolver.hpp b/uno/ingredients/subproblem_solvers/HiGHS/HiGHSSolver.hpp
similarity index 96%
rename from uno/solvers/HiGHS/HiGHSSolver.hpp
rename to uno/ingredients/subproblem_solvers/HiGHS/HiGHSSolver.hpp
index 5f78285b..277e9b63 100644
--- a/uno/solvers/HiGHS/HiGHSSolver.hpp
+++ b/uno/ingredients/subproblem_solvers/HiGHS/HiGHSSolver.hpp
@@ -1,7 +1,7 @@
 #ifndef UNO_HIGHSSOLVER_H
 #define UNO_HIGHSSOLVER_H
 
-#include "solvers/LPSolver.hpp"
+#include "ingredients/subproblem_solvers/LPSolver.hpp"
 #include "Highs.h"
 
 namespace uno {
diff --git a/uno/solvers/LPSolver.hpp b/uno/ingredients/subproblem_solvers/LPSolver.hpp
similarity index 100%
rename from uno/solvers/LPSolver.hpp
rename to uno/ingredients/subproblem_solvers/LPSolver.hpp
diff --git a/uno/solvers/LPSolverFactory.cpp b/uno/ingredients/subproblem_solvers/LPSolverFactory.cpp
similarity index 93%
rename from uno/solvers/LPSolverFactory.cpp
rename to uno/ingredients/subproblem_solvers/LPSolverFactory.cpp
index 528b85a6..d17bb1b6 100644
--- a/uno/solvers/LPSolverFactory.cpp
+++ b/uno/ingredients/subproblem_solvers/LPSolverFactory.cpp
@@ -5,13 +5,13 @@
 #include "LPSolverFactory.hpp"
 #include "linear_algebra/Vector.hpp"
 #include "options/Options.hpp"
-#include "solvers/LPSolver.hpp"
+#include "LPSolver.hpp"
 
 #ifdef HAS_BQPD
-#include "solvers/BQPD/BQPDSolver.hpp"
+#include "ingredients/subproblem_solvers/BQPD/BQPDSolver.hpp"
 #endif
 #ifdef HAS_HIGHS
-#include "solvers/HiGHS/HiGHSSolver.hpp"
+#include "ingredients/subproblem_solvers/HiGHS/HiGHSSolver.hpp"
 #endif
 
 namespace uno {
diff --git a/uno/solvers/LPSolverFactory.hpp b/uno/ingredients/subproblem_solvers/LPSolverFactory.hpp
similarity index 100%
rename from uno/solvers/LPSolverFactory.hpp
rename to uno/ingredients/subproblem_solvers/LPSolverFactory.hpp
diff --git a/uno/solvers/MA27/MA27Solver.cpp b/uno/ingredients/subproblem_solvers/MA27/MA27Solver.cpp
similarity index 100%
rename from uno/solvers/MA27/MA27Solver.cpp
rename to uno/ingredients/subproblem_solvers/MA27/MA27Solver.cpp
diff --git a/uno/solvers/MA27/MA27Solver.hpp b/uno/ingredients/subproblem_solvers/MA27/MA27Solver.hpp
similarity index 97%
rename from uno/solvers/MA27/MA27Solver.hpp
rename to uno/ingredients/subproblem_solvers/MA27/MA27Solver.hpp
index 59895648..12bb5c4f 100644
--- a/uno/solvers/MA27/MA27Solver.hpp
+++ b/uno/ingredients/subproblem_solvers/MA27/MA27Solver.hpp
@@ -6,7 +6,7 @@
 
 #include <array>
 #include <vector>
-#include "solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
+#include "../DirectSymmetricIndefiniteLinearSolver.hpp"
 
 namespace uno {
    // forward declaration
diff --git a/uno/solvers/MA57/MA57Solver.cpp b/uno/ingredients/subproblem_solvers/MA57/MA57Solver.cpp
similarity index 100%
rename from uno/solvers/MA57/MA57Solver.cpp
rename to uno/ingredients/subproblem_solvers/MA57/MA57Solver.cpp
diff --git a/uno/solvers/MA57/MA57Solver.hpp b/uno/ingredients/subproblem_solvers/MA57/MA57Solver.hpp
similarity index 96%
rename from uno/solvers/MA57/MA57Solver.hpp
rename to uno/ingredients/subproblem_solvers/MA57/MA57Solver.hpp
index 33f9c524..31d1d17f 100644
--- a/uno/solvers/MA57/MA57Solver.hpp
+++ b/uno/ingredients/subproblem_solvers/MA57/MA57Solver.hpp
@@ -6,7 +6,7 @@
 
 #include <array>
 #include <vector>
-#include "solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
+#include "ingredients/subproblem_solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
 
 namespace uno {
    // forward declaration
diff --git a/uno/solvers/MUMPS/MUMPSSolver.cpp b/uno/ingredients/subproblem_solvers/MUMPS/MUMPSSolver.cpp
similarity index 100%
rename from uno/solvers/MUMPS/MUMPSSolver.cpp
rename to uno/ingredients/subproblem_solvers/MUMPS/MUMPSSolver.cpp
diff --git a/uno/solvers/MUMPS/MUMPSSolver.hpp b/uno/ingredients/subproblem_solvers/MUMPS/MUMPSSolver.hpp
similarity index 96%
rename from uno/solvers/MUMPS/MUMPSSolver.hpp
rename to uno/ingredients/subproblem_solvers/MUMPS/MUMPSSolver.hpp
index da7ebd98..b18f18d1 100644
--- a/uno/solvers/MUMPS/MUMPSSolver.hpp
+++ b/uno/ingredients/subproblem_solvers/MUMPS/MUMPSSolver.hpp
@@ -5,7 +5,7 @@
 #define UNO_MUMPSSOLVER_H
 
 #include <vector>
-#include "solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
+#include "../DirectSymmetricIndefiniteLinearSolver.hpp"
 #include "dmumps_c.h"
 
 namespace uno {
diff --git a/uno/solvers/QPSolver.hpp b/uno/ingredients/subproblem_solvers/QPSolver.hpp
similarity index 98%
rename from uno/solvers/QPSolver.hpp
rename to uno/ingredients/subproblem_solvers/QPSolver.hpp
index fb1e93c0..e63f74ad 100644
--- a/uno/solvers/QPSolver.hpp
+++ b/uno/ingredients/subproblem_solvers/QPSolver.hpp
@@ -5,7 +5,7 @@
 #define UNO_QPSOLVER_H
 
 #include <vector>
-#include "solvers/LPSolver.hpp"
+#include "LPSolver.hpp"
 
 namespace uno {
    // forward declarations
diff --git a/uno/solvers/QPSolverFactory.cpp b/uno/ingredients/subproblem_solvers/QPSolverFactory.cpp
similarity index 95%
rename from uno/solvers/QPSolverFactory.cpp
rename to uno/ingredients/subproblem_solvers/QPSolverFactory.cpp
index ea71c71c..5cb00424 100644
--- a/uno/solvers/QPSolverFactory.cpp
+++ b/uno/ingredients/subproblem_solvers/QPSolverFactory.cpp
@@ -5,10 +5,10 @@
 #include "QPSolverFactory.hpp"
 #include "linear_algebra/Vector.hpp"
 #include "options/Options.hpp"
-#include "solvers/QPSolver.hpp"
+#include "QPSolver.hpp"
 
 #ifdef HAS_BQPD
-#include "solvers/BQPD/BQPDSolver.hpp"
+#include "ingredients/subproblem_solvers/BQPD/BQPDSolver.hpp"
 #endif
 
 namespace uno {
diff --git a/uno/solvers/QPSolverFactory.hpp b/uno/ingredients/subproblem_solvers/QPSolverFactory.hpp
similarity index 100%
rename from uno/solvers/QPSolverFactory.hpp
rename to uno/ingredients/subproblem_solvers/QPSolverFactory.hpp
diff --git a/uno/solvers/SymmetricIndefiniteLinearSolver.hpp b/uno/ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolver.hpp
similarity index 100%
rename from uno/solvers/SymmetricIndefiniteLinearSolver.hpp
rename to uno/ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolver.hpp
diff --git a/uno/solvers/SymmetricIndefiniteLinearSolverFactory.cpp b/uno/ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.cpp
similarity index 93%
rename from uno/solvers/SymmetricIndefiniteLinearSolverFactory.cpp
rename to uno/ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.cpp
index 1d83c324..89e1b9df 100644
--- a/uno/solvers/SymmetricIndefiniteLinearSolverFactory.cpp
+++ b/uno/ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.cpp
@@ -9,11 +9,11 @@
 #include "options/Options.hpp"
 
 #if defined(HAS_HSL) || defined(HAS_MA57)
-#include "solvers/MA57/MA57Solver.hpp"
+#include "ingredients/subproblem_solvers/MA57/MA57Solver.hpp"
 #endif
 
 #if defined(HAS_HSL) || defined(HAS_MA27)
-#include "solvers/MA27/MA27Solver.hpp"
+#include "ingredients/subproblem_solvers/MA27/MA27Solver.hpp"
 #endif
 
 #ifdef HAS_HSL
@@ -25,7 +25,7 @@ namespace uno {
 #endif
 
 #ifdef HAS_MUMPS
-#include "solvers/MUMPS/MUMPSSolver.hpp"
+#include "ingredients/subproblem_solvers/MUMPS/MUMPSSolver.hpp"
 #endif
 
 namespace uno {
diff --git a/uno/solvers/SymmetricIndefiniteLinearSolverFactory.hpp b/uno/ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.hpp
similarity index 100%
rename from uno/solvers/SymmetricIndefiniteLinearSolverFactory.hpp
rename to uno/ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.hpp
diff --git a/uno/linear_algebra/SymmetricIndefiniteLinearSystem.hpp b/uno/linear_algebra/SymmetricIndefiniteLinearSystem.hpp
index 700ed50c..ed2e3f30 100644
--- a/uno/linear_algebra/SymmetricIndefiniteLinearSystem.hpp
+++ b/uno/linear_algebra/SymmetricIndefiniteLinearSystem.hpp
@@ -9,8 +9,8 @@
 #include "SparseStorageFactory.hpp"
 #include "RectangularMatrix.hpp"
 #include "ingredients/hessian_models/UnstableRegularization.hpp"
+#include "ingredients/subproblem_solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
 #include "model/Model.hpp"
-#include "solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
 #include "options/Options.hpp"
 #include "tools/Statistics.hpp"
 
diff --git a/uno/options/DefaultOptions.cpp b/uno/options/DefaultOptions.cpp
index 3088bb5c..348e023a 100644
--- a/uno/options/DefaultOptions.cpp
+++ b/uno/options/DefaultOptions.cpp
@@ -2,9 +2,9 @@
 // Licensed under the MIT license. See LICENSE file in the project directory for details.
 
 #include "DefaultOptions.hpp"
-#include "solvers/QPSolverFactory.hpp"
-#include "solvers/LPSolverFactory.hpp"
-#include "solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
+#include "ingredients/subproblem_solvers/QPSolverFactory.hpp"
+#include "ingredients/subproblem_solvers/LPSolverFactory.hpp"
+#include "ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
 
 namespace uno {
    Options DefaultOptions::load() {
diff --git a/uno/options/Presets.cpp b/uno/options/Presets.cpp
index 369271a0..a5086fcd 100644
--- a/uno/options/Presets.cpp
+++ b/uno/options/Presets.cpp
@@ -4,9 +4,9 @@
 #include <stdexcept>
 #include "Presets.hpp"
 #include "Options.hpp"
-#include "solvers/LPSolverFactory.hpp"
-#include "solvers/QPSolverFactory.hpp"
-#include "solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
+#include "ingredients/subproblem_solvers/LPSolverFactory.hpp"
+#include "ingredients/subproblem_solvers/QPSolverFactory.hpp"
+#include "ingredients/subproblem_solvers/SymmetricIndefiniteLinearSolverFactory.hpp"
 
 namespace uno {
    Options Presets::get_preset_options(const std::optional<std::string>& optional_preset) {
diff --git a/uno/preprocessing/Preprocessing.cpp b/uno/preprocessing/Preprocessing.cpp
index 00584c19..1221e296 100644
--- a/uno/preprocessing/Preprocessing.cpp
+++ b/uno/preprocessing/Preprocessing.cpp
@@ -2,14 +2,14 @@
 // Licensed under the MIT license. See LICENSE file in the project directory for details.
 
 #include "Preprocessing.hpp"
-#include "optimization/Direction.hpp"
+#include "ingredients/subproblem_solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
+#include "ingredients/subproblem_solvers/QPSolver.hpp"
 #include "linear_algebra/SymmetricMatrix.hpp"
 #include "linear_algebra/RectangularMatrix.hpp"
 #include "model/Model.hpp"
+#include "optimization/Direction.hpp"
 #include "optimization/Iterate.hpp"
 #include "optimization/WarmstartInformation.hpp"
-#include "solvers/DirectSymmetricIndefiniteLinearSolver.hpp"
-#include "solvers/QPSolver.hpp"
 #include "symbolic/VectorView.hpp"
 
 namespace uno {
diff --git a/unotest/functional_tests/BQPDSolverTests.cpp b/unotest/functional_tests/BQPDSolverTests.cpp
index 28c4996e..69b4b55d 100644
--- a/unotest/functional_tests/BQPDSolverTests.cpp
+++ b/unotest/functional_tests/BQPDSolverTests.cpp
@@ -2,13 +2,13 @@
 // Licensed under the MIT license. See LICENSE file in the project directory for details.
 
 #include <gtest/gtest.h>
-#include "optimization/Direction.hpp"
+#include "ingredients/subproblem_solvers/BQPD/BQPDSolver.hpp"
 #include "linear_algebra/RectangularMatrix.hpp"
 #include "linear_algebra/SparseVector.hpp"
 #include "linear_algebra/SymmetricMatrix.hpp"
+#include "optimization/Direction.hpp"
 #include "optimization/WarmstartInformation.hpp"
 #include "options/Options.hpp"
-#include "solvers/BQPD/BQPDSolver.hpp"
 #include "tools/Infinity.hpp"
 
 using namespace uno;
diff --git a/unotest/functional_tests/HiGHSSolverTests.cpp b/unotest/functional_tests/HiGHSSolverTests.cpp
index de7aea69..0381ee94 100644
--- a/unotest/functional_tests/HiGHSSolverTests.cpp
+++ b/unotest/functional_tests/HiGHSSolverTests.cpp
@@ -2,12 +2,12 @@
 // Licensed under the MIT license. See LICENSE file in the project directory for details.
 
 #include <gtest/gtest.h>
-#include "optimization/Direction.hpp"
+#include "ingredients/subproblem_solvers/HiGHS/HiGHSSolver.hpp"
 #include "linear_algebra/RectangularMatrix.hpp"
 #include "linear_algebra/SparseVector.hpp"
+#include "optimization/Direction.hpp"
 #include "optimization/WarmstartInformation.hpp"
 #include "options/Options.hpp"
-#include "solvers/HiGHS/HiGHSSolver.hpp"
 #include "tools/Infinity.hpp"
 
 using namespace uno;
diff --git a/unotest/functional_tests/MA27SolverTests.cpp b/unotest/functional_tests/MA27SolverTests.cpp
index a123a817..b0f4f443 100644
--- a/unotest/functional_tests/MA27SolverTests.cpp
+++ b/unotest/functional_tests/MA27SolverTests.cpp
@@ -2,8 +2,8 @@
 // Licensed under the MIT license. See LICENSE file in the project directory for details.
 
 #include <gtest/gtest.h>
+#include "ingredients/subproblem_solvers/MA27/MA27Solver.hpp"
 #include "linear_algebra/SymmetricMatrix.hpp"
-#include "solvers/MA27/MA27Solver.hpp"
 
 using namespace uno;
 
diff --git a/unotest/functional_tests/MA57SolverTests.cpp b/unotest/functional_tests/MA57SolverTests.cpp
index a75eb355..001b2953 100644
--- a/unotest/functional_tests/MA57SolverTests.cpp
+++ b/unotest/functional_tests/MA57SolverTests.cpp
@@ -2,8 +2,8 @@
 // Licensed under the MIT license. See LICENSE file in the project directory for details.
 
 #include <gtest/gtest.h>
+#include "ingredients/subproblem_solvers/MA57/MA57Solver.hpp"
 #include "linear_algebra/SymmetricMatrix.hpp"
-#include "solvers/MA57/MA57Solver.hpp"
 
 using namespace uno;
 
diff --git a/unotest/functional_tests/MUMPSSolverTests.cpp b/unotest/functional_tests/MUMPSSolverTests.cpp
index a886c9a0..28a48f8f 100644
--- a/unotest/functional_tests/MUMPSSolverTests.cpp
+++ b/unotest/functional_tests/MUMPSSolverTests.cpp
@@ -2,8 +2,8 @@
 // Licensed under the MIT license. See LICENSE file in the project directory for details.
 
 #include <gtest/gtest.h>
+#include "ingredients/subproblem_solvers/MUMPS/MUMPSSolver.hpp"
 #include "linear_algebra/SymmetricMatrix.hpp"
-#include "solvers/MUMPS/MUMPSSolver.hpp"
 
 using namespace uno;