Bug fix : Coarse patch dx for external field init (#3674)

* fix coarse patch dx for external field init

* rename var

* Update Source/Initialization/WarpXInitData.cpp

Co-authored-by: Axel Huebl <[email protected]>

* reset benchmark for PEC_mr test case

---------

Co-authored-by: Axel Huebl <[email protected]>

Author: RevathiJambunathan

Regression/Checksum/benchmarks_json/PEC_field_mr.json

@@ -4,7 +4,7 @@
     "Ey": 1052208601.720587
   },
   "lev=1": {
-    "Bx": 0.3187370090421958,
-    "Ey": 98224588.87142882
+    "Bx": 0.038732896603981076,
+    "Ey": 9503300.083366634
   }
 }

Source/Initialization/WarpXInitData.cpp

@@ -756,7 +756,7 @@ WarpX::InitLevelData (int lev, Real /*time*/)
                                                  m_edge_lengths[lev],
                                                  m_face_areas[lev],
                                                  'B',
-                                                 lev);
+                                                 lev, PatchType::fine);
        if (lev > 0) {
           InitializeExternalFieldsOnGridUsingParser(Bfield_aux[lev][0].get(),
                                                     Bfield_aux[lev][1].get(),
@@ -767,7 +767,7 @@ WarpX::InitLevelData (int lev, Real /*time*/)
                                                     m_edge_lengths[lev],
                                                     m_face_areas[lev],
                                                     'B',
-                                                    lev);
+                                                    lev, PatchType::fine);
 
           InitializeExternalFieldsOnGridUsingParser(Bfield_cp[lev][0].get(),
                                                     Bfield_cp[lev][1].get(),
@@ -778,7 +778,7 @@ WarpX::InitLevelData (int lev, Real /*time*/)
                                                     m_edge_lengths[lev],
                                                     m_face_areas[lev],
                                                     'B',
-                                                    lev);
+                                                    lev, PatchType::coarse);
        }
     }
 
@@ -815,7 +815,7 @@ WarpX::InitLevelData (int lev, Real /*time*/)
                                                  m_edge_lengths[lev],
                                                  m_face_areas[lev],
                                                  'E',
-                                                 lev);
+                                                 lev, PatchType::fine);
 
 #ifdef AMREX_USE_EB
         // We initialize ECTRhofield consistently with the Efield
@@ -836,7 +836,7 @@ WarpX::InitLevelData (int lev, Real /*time*/)
                                                     m_edge_lengths[lev],
                                                     m_face_areas[lev],
                                                     'E',
-                                                    lev);
+                                                    lev, PatchType::fine);
 
           InitializeExternalFieldsOnGridUsingParser(Efield_cp[lev][0].get(),
                                                     Efield_cp[lev][1].get(),
@@ -847,7 +847,7 @@ WarpX::InitLevelData (int lev, Real /*time*/)
                                                     m_edge_lengths[lev],
                                                     m_face_areas[lev],
                                                     'E',
-                                                    lev);
+                                                    lev, PatchType::coarse);
 #ifdef AMREX_USE_EB
            if (WarpX::electromagnetic_solver_id == ElectromagneticSolverAlgo::ECT) {
                // We initialize ECTRhofield consistently with the Efield
@@ -876,10 +876,16 @@ WarpX::InitializeExternalFieldsOnGridUsingParser (
        std::array< std::unique_ptr<amrex::MultiFab>, 3 > const& edge_lengths,
        std::array< std::unique_ptr<amrex::MultiFab>, 3 > const& face_areas,
        const char field,
-       const int lev)
+       const int lev, PatchType patch_type)
 {
 
-    const auto dx_lev = geom[lev].CellSizeArray();
+    auto dx_lev = geom[lev].CellSizeArray();
+    amrex::IntVect refratio = (lev > 0 ) ? WarpX::RefRatio(lev-1) : amrex::IntVect(1);
+    if (patch_type == PatchType::coarse) {
+        for (int idim = 0; idim < AMREX_SPACEDIM; ++idim) {
+            dx_lev[idim] = dx_lev[idim] * refratio[idim];
+        }
+    }
     const RealBox& real_box = geom[lev].ProbDomain();
     amrex::IntVect x_nodal_flag = mfx->ixType().toIntVect();
     amrex::IntVect y_nodal_flag = mfy->ixType().toIntVect();

Source/WarpX.H

@@ -924,6 +924,7 @@ public:
      * \param[in] face_areas face areas information
      * \param[in] field flag indicating which field is being initialized ('E' for electric, 'B' for magnetic)
      * \param[in] lev level of the Multifabs that is initialized
+     * \param[in] patch_type PatchType on which the field is initialized (fine or coarse)
      */
     void InitializeExternalFieldsOnGridUsingParser (
          amrex::MultiFab *mfx, amrex::MultiFab *mfy, amrex::MultiFab *mfz,
@@ -933,7 +934,7 @@ public:
          std::array< std::unique_ptr<amrex::MultiFab>, 3 > const& edge_lengths,
          std::array< std::unique_ptr<amrex::MultiFab>, 3 > const& face_areas,
          const char field,
-         const int lev);
+         const int lev, PatchType patch_type);
 
     /**
      * \brief