Optimization of multigrid settings (#2772)

Author: bigfooted

Common/include/CConfig.hpp

@@ -472,7 +472,7 @@ class CConfig {
   string CustomObjFunc;        /*!< \brief User-defined objective function. */
   string CustomOutputs;        /*!< \brief User-defined functions for outputs. */
   unsigned short nDV,                  /*!< \brief Number of design variables. */
-  nObj, nObjW;                         /*! \brief Number of objective functions. */
+  nObj, nObjW;                         /*!< \brief Number of objective functions. */
   unsigned short* nDV_Value;           /*!< \brief Number of values for each design variable (might be different than 1 if we allow arbitrary movement). */
   unsigned short nFFDBox;              /*!< \brief Number of ffd boxes. */
   unsigned short nTurboMachineryKind;  /*!< \brief Number turbomachinery types specified. */
@@ -489,20 +489,14 @@ class CConfig {
   string *FFDTag;                     /*!< \brief Parameters of the design variable. */
   string *TagFFDBox;                  /*!< \brief Tag of the FFD box. */
   unsigned short GeometryMode;        /*!< \brief Geometry mode (analysis or gradient computation). */
-  unsigned short MGCycle;             /*!< \brief Kind of multigrid cycle. */
   unsigned short FinestMesh;          /*!< \brief Finest mesh for the full multigrid approach. */
   unsigned short nFFD_Fix_IDir,
   nFFD_Fix_JDir, nFFD_Fix_KDir;       /*!< \brief Number of planes fixed in the FFD. */
-  unsigned short nMG_PreSmooth,       /*!< \brief Number of MG pre-smooth parameters found in config file. */
-  nMG_PostSmooth,                     /*!< \brief Number of MG post-smooth parameters found in config file. */
-  nMG_CorrecSmooth;                   /*!< \brief Number of MG correct-smooth parameters found in config file. */
   short *FFD_Fix_IDir,
   *FFD_Fix_JDir, *FFD_Fix_KDir;       /*!< \brief Exact sections. */
-  unsigned short *MG_PreSmooth,       /*!< \brief Multigrid Pre smoothing. */
-  *MG_PostSmooth,                     /*!< \brief Multigrid Post smoothing. */
-  *MG_CorrecSmooth;                   /*!< \brief Multigrid Jacobi implicit smoothing of the correction. */
   su2double *LocationStations;        /*!< \brief Airfoil sections in wing slicing subroutine. */
 
+  MG_CYCLE Kind_MGCycle;              /*!< \brief Kind of multigrid cycle. */
   ENUM_MULTIZONE Kind_MZSolver;    /*!< \brief Kind of multizone solver.  */
   INC_DENSITYMODEL Kind_DensityModel; /*!< \brief Kind of the density model for incompressible flows. */
   CHT_COUPLING Kind_CHT_Coupling;  /*!< \brief Kind of coupling method used at CHT interfaces. */
@@ -1132,6 +1126,10 @@ class CConfig {
     unsigned long rampMUSCLCoeff[3];     /*!< \brief ramp MUSCL value coefficients for the COption class. */
   } RampMUSCLParam;
   su2double rampMUSCLValue; /*!< \brief Current value of the MUSCL ramp */
+  CMGOptions MGOptions;
+  /*--- Multigrid options  ---*/
+  unsigned short nMG_PreSmooth_p{0}, nMG_PostSmooth_p{0}, nMG_CorrecSmooth_p{0};
+  unsigned short *MG_PreSmooth_p{nullptr}, *MG_PostSmooth_p{nullptr}, *MG_CorrecSmooth_p{nullptr};
 
   ENUM_STREAMWISE_PERIODIC Kind_Streamwise_Periodic; /*!< \brief Kind of Streamwise periodic flow (pressure drop or massflow) */
   bool Streamwise_Periodic_Temperature;              /*!< \brief Use real periodicity for Energy equation or otherwise outlet source term. */
@@ -2908,7 +2906,7 @@ class CConfig {
    */
   void SetMGLevels(unsigned short val_nMGLevels) {
     nMGLevels = val_nMGLevels;
-    if (MGCycle == FULLMG_CYCLE) {
+    if (Kind_MGCycle == MG_CYCLE::FULL) {
       SetFinestMesh(val_nMGLevels);
     }
   }
@@ -2925,7 +2923,7 @@ class CConfig {
    * \note This variable is used in a recursive way to perform the different kind of cycles
    * \return 0 or 1 depending of we are dealing with a V or W cycle.
    */
-  unsigned short GetMGCycle(void) const { return MGCycle; }
+  MG_CYCLE GetMGCycle(void) const { return Kind_MGCycle; }
 
   /*!
    * \brief Get the king of evaluation in the geometrical module.
@@ -3847,34 +3845,9 @@ class CConfig {
   su2double GetNacelleLocation(unsigned short val_index) const { return nacelle_location[val_index]; }
 
   /*!
-   * \brief Get the number of pre-smoothings in a multigrid strategy.
-   * \param[in] val_mesh - Index of the grid.
-   * \return Number of smoothing iterations.
+   * \brief Get the multigrid options struct.
    */
-  unsigned short GetMG_PreSmooth(unsigned short val_mesh) const {
-    if (nMG_PreSmooth == 0) return 1;
-    return MG_PreSmooth[val_mesh];
-  }
-
-  /*!
-   * \brief Get the number of post-smoothings in a multigrid strategy.
-   * \param[in] val_mesh - Index of the grid.
-   * \return Number of smoothing iterations.
-   */
-  unsigned short GetMG_PostSmooth(unsigned short val_mesh) const {
-    if (nMG_PostSmooth == 0) return 0;
-    return MG_PostSmooth[val_mesh];
-  }
-
-  /*!
-   * \brief Get the number of implicit Jacobi smoothings of the correction in a multigrid strategy.
-   * \param[in] val_mesh - Index of the grid.
-   * \return Number of implicit smoothing iterations.
-   */
-  unsigned short GetMG_CorrecSmooth(unsigned short val_mesh) const {
-    if (nMG_CorrecSmooth == 0) return 0;
-    return MG_CorrecSmooth[val_mesh];
-  }
+  const CMGOptions& GetMGOptions() const { return MGOptions; }
 
   /*!
    * \brief plane of the FFD (I axis) that should be fixed.
@@ -6833,12 +6806,24 @@ class CConfig {
    */
   su2double GetDamp_Res_Restric(void) const { return Damp_Res_Restric; }
 
+  /*!
+   * \brief Set the damping factor for the residual restriction (used by adaptive MG damping).
+   * \param[in] val - New damping factor value.
+   */
+  void SetDamp_Res_Restric(su2double val) { Damp_Res_Restric = val; }
+
   /*!
    * \brief Value of the damping factor for the correction prolongation.
    * \return Value of the damping factor.
    */
   su2double GetDamp_Correc_Prolong(void) const { return Damp_Correc_Prolong; }
 
+  /*!
+   * \brief Set the damping factor for the correction prolongation (used by adaptive MG damping).
+   * \param[in] val - New damping factor value.
+   */
+  void SetDamp_Correc_Prolong(su2double val) { Damp_Correc_Prolong = val; }
+
   /*!
    * \brief Value of the position of the Near Field (y coordinate for 2D, and z coordinate for 3D).
    * \return Value of the Near Field position.

Common/include/geometry/CGeometry.hpp

@@ -811,10 +811,13 @@ class CGeometry {
   inline virtual void MatchActuator_Disk(const CConfig* config) {}
 
   /*!
-   * \brief A virtual member.
+   * \brief Match periodic boundary points using coordinate-based matching.
+   * \details Gathers coordinates from all ranks via MPI, applies the rotation/translation
+   * for the periodic pair, and finds the nearest neighbor. Works on both fine and coarse grids.
    * \param[in] config - Definition of the particular problem.
+   * \param[in] val_periodic - Index of the periodic marker pair.
    */
-  inline virtual void MatchPeriodic(const CConfig* config, unsigned short val_periodic) {}
+  virtual void MatchPeriodic(const CConfig* config, unsigned short val_periodic);
 
   /*!
    * \brief A virtual member.
@@ -1609,12 +1612,6 @@ class CGeometry {
     return AverageGridVel[val_marker][val_span];
   }
 
-  /*!
-   * \brief A virtual member.
-   * \param config - Config
-   */
-  inline virtual void Check_Periodicity(CConfig* config) {}
-
   /*!
    * \brief Get the value of the customized temperature at a specified vertex on a specified marker.
    * \param[in] val_marker - Marker value

Common/include/geometry/CMultiGridGeometry.hpp

@@ -29,6 +29,8 @@
 
 #include "CGeometry.hpp"
 
+class CMultiGridQueue;
+
 /*!
  * \class CMultiGridGeometry
  * \brief Class for defining the multigrid geometry, the main dedicated part is the
@@ -75,6 +77,16 @@ class CMultiGridGeometry final : public CGeometry {
    */
   su2double ComputeLocalCurvature(const CGeometry* fine_grid, unsigned long iPoint, unsigned short iMarker) const;
 
+  /*!
+   * \brief Agglomerate high-aspect-ratio interior cells along implicit lines from wall vertices.
+   * \param[in,out] Index_CoarseCV - Current coarse CV index, incremented as new coarse CVs are created.
+   * \param[in] fine_grid - Fine grid geometry.
+   * \param[in] config - Configuration.
+   * \param[in,out] MGQueue_InnerCV - Queue for domain agglomeration; processed points are removed.
+   */
+  void AgglomerateImplicitLines(unsigned long& Index_CoarseCV, const CGeometry* fine_grid, const CConfig* config,
+                                CMultiGridQueue& MGQueue_InnerCV);
+
  public:
   /*--- This is to suppress Woverloaded-virtual, omitting it has no negative impact. ---*/
   using CGeometry::SetBoundControlVolume;
@@ -143,13 +155,6 @@ class CMultiGridGeometry final : public CGeometry {
    */
   void MatchActuator_Disk(const CConfig* config) override;
 
-  /*!
-   * \brief Mach the periodic boundary conditions.
-   * \param[in] config - Definition of the particular problem.
-   * \param[in] val_periodic - Index of the first periodic face in a pair.
-   */
-  void MatchPeriodic(const CConfig* config, unsigned short val_periodic) override;
-
   /*!
    * \brief Set a representative wall normal heat flux of the agglomerated control volume on a particular boundary
    * marker. \param[in] fine_grid - Geometrical definition of the problem. \param[in] val_marker - Index of the boundary

Common/include/geometry/CPhysicalGeometry.hpp

@@ -438,13 +438,6 @@ class CPhysicalGeometry final : public CGeometry {
    */
   void MatchActuator_Disk(const CConfig* config) override;
 
-  /*!
-   * \brief Mach the periodic boundary conditions.
-   * \param[in] config - Definition of the particular problem.
-   * \param[in] val_periodic - Index of the first periodic face in a pair.
-   */
-  void MatchPeriodic(const CConfig* config, unsigned short val_periodic) override;
-
   /*!
    * \brief Set boundary vertex structure of the control volume.
    * \param[in] config - Definition of the particular problem.
@@ -779,12 +772,6 @@ class CPhysicalGeometry final : public CGeometry {
     Sensitivity(iPoint, iDim) = val;
   }
 
-  /*!
-   * \brief Check the mesh for periodicity and deactivate multigrid if periodicity is found.
-   * \param[in] config - Definition of the particular problem.
-   */
-  void Check_Periodicity(CConfig* config) override;
-
   /*!
    * \brief Compute an ADT including the coordinates of all viscous markers
    * \param[in] config - Definition of the particular problem.

Common/include/linear_algebra/CSysSolve.hpp

@@ -196,7 +196,7 @@ class CSysSolve {
    * vector is kept in nrm0 and updated after operating with each vector
    *
    */
-  void ModGramSchmidt(bool shared_hsbg, int i, su2matrix<ScalarType>& Hsbg, std::vector<VectorType>& w) const;
+  bool ModGramSchmidt(bool shared_hsbg, int i, su2matrix<ScalarType>& Hsbg, std::vector<VectorType>& w) const;
 
   /*!
    * \brief writes header information for a CSysSolve residual history

Common/include/option_structure.hpp

@@ -1101,6 +1101,21 @@ inline SST_ParsedOptions ParseSSTOptions(const SST_OPTIONS *SST_Options, unsigne
   return SSTParsedOptions;
 }
 
+/*!
+ * \brief Structure containing multigrid options.
+ */
+struct CMGOptions {
+  su2double MG_Smooth_Res_Threshold{0.0}; /*!< \brief RMS reduction threshold for MG smoothing early exit. */
+  su2double MG_Smooth_Coeff{0.0};         /*!< \brief Jacobi smoother coefficient for coarse-grid correction. */
+  unsigned long MG_Min_MeshSize{0};       /*!< \brief Minimum CVs on coarsest MG level. */
+  std::vector<unsigned short> MG_PreSmooth;    /*!< \brief Multigrid pre-smoothing iterations per level. */
+  std::vector<unsigned short> MG_PostSmooth;   /*!< \brief Multigrid post-smoothing iterations per level. */
+  std::vector<unsigned short> MG_CorrecSmooth; /*!< \brief Multigrid Jacobi correction-smoothing per level. */
+  bool MG_Smooth_EarlyExit{false};        /*!< \brief Enable early exit for MG smoothing iterations. */
+  bool MG_Smooth_Output{false};           /*!< \brief Output compact per-cycle smoothing summary. */
+  bool MG_Implicit_Lines{false};          /*!< \brief Enable implicit-lines agglomeration from walls. */
+};
+
 /*!
  * \brief SST rough-wall boundary conditions Options
  */
@@ -2281,17 +2296,17 @@ static const MapType<std::string, JUMP_DEFINITION> Jump_Map = {
 /*!
  * \brief Type of multigrid cycle
  */
-enum MG_CYCLE {
-  V_CYCLE = 0,        /*!< \brief V cycle. */
-  W_CYCLE = 1,        /*!< \brief W cycle. */
-  FULLMG_CYCLE = 2    /*!< \brief FullMG cycle. */
+enum class MG_CYCLE {
+  V,  /*!< \brief V-cycle multigrid solver. */
+  W,  /*!< \brief W-cycle multigrid solver. */
+  FULL, /*!< \brief Full multigrid (FMG) solver. */
 };
+
 static const MapType<std::string, MG_CYCLE> MG_Cycle_Map = {
-  MakePair("V_CYCLE", V_CYCLE)
-  MakePair("W_CYCLE", W_CYCLE)
-  MakePair("FULLMG_CYCLE", FULLMG_CYCLE)
+  MakePair("V_CYCLE", MG_CYCLE::V)
+  MakePair("W_CYCLE", MG_CYCLE::W)
+  MakePair("FULLMG_CYCLE", MG_CYCLE::FULL)
 };
-
 /*!
  * \brief Types of design parameterizations
  */