BTD fields with RZ + openPMD - single mode only (ECP-WarpX#3350)

* cell center BTD functors for RZ with openpmd

* add RZ modes to output varnames too

* update varnames once and set map for RZ fields in BTfunctor

* fix access to varname field instead of unallocated m_varnames, and update hi ki-index after flush

* set back trasnformed fields to false if fields_to_plot is none. Separate PArticle and Field io further. Also, clean up Particle Buffer initialize so its consistent with Field box, boxarray, dmap, and geom

* clean commented line

* assert for single rz mode

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* remove unused var

* Apply suggestions from code review

From Axels' review

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

* adding comments, doxygen, and clean-up

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Axel Huebl <[email protected]>

Source/Diagnostics/BTDiagnostics.H

@@ -74,6 +74,25 @@ private:
      *                is initialized.
      */
     void InitializeFieldFunctors (int lev) override;
+    /** Initialize functors that store pointers to the fields in RZ requested by the user.
+     *  Additionally, the cell-center functors that stores pointers to all fields,
+     *  namely, Er, Et, Ez, Br, Bt, Bz, jr, jt, jz, and rho is also initialized.
+     * \param[in] lev level on which the vector of unique_ptrs to field functors
+     *                is initialized.
+     */
+    void InitializeFieldFunctorsRZopenPMD (int lev) override;
+    /** Populating m_varnames with real and imaginary parts of each RZ mode.
+     *  Modes are numbered from 0 to (nmodes-1) and mode 0 is purely real.
+     *  Both m_cellcenter_varnames (storing cell-centered data) and
+     *  m_varnames (storing back-transformed field data) are modified to include RZ modes to include
+     *  field_modeid_real/imag. For example, for Er with two modes, the varnames are
+     *  Er_0_real, Er_1_real, Er_1_imag
+     * \param[in] field field-name
+     * \param[in] ncomp number of rz components (if 2 modes, the ncomp is 2*nmodes-1)
+     * \param[in] cellcenter_data if true, m_cellcenter_varnames are updated
+                                  if false, m_varnames is updated
+     */
+    void AddRZModesToOutputNames (const std::string& field, const int ncomp, bool cellcenter_data);
     /** This function allocates and initializes particle buffers for all the snapshots.
      * This is currently an empty function:
      * The particle containers required for this must be added to populate this function.
@@ -313,9 +332,20 @@ private:
      *  All the fields are stored regardless of the specific fields to plot selected
      *  by the user.
      */
+#ifdef WARPX_DIM_RZ
+    amrex::Vector< std::string > m_cellcenter_varnames = {"Er", "Et", "Ez",
+                                                          "Br", "Bt", "Bz",
+                                                          "jr", "jt", "jz", "rho"};
+    amrex::Vector< std::string > m_cellcenter_varnames_fields = {"Er", "Et", "Ez",
+                                                                 "Br", "Bt", "Bz",
+                                                                 "jr", "jt", "jz",
+                                                                 "rho"};
+#else
     amrex::Vector< std::string > m_cellcenter_varnames = {"Ex", "Ey", "Ez",
                                                           "Bx", "By", "Bz",
                                                           "jx", "jy", "jz", "rho"};
+#endif
+
 
     /** Merge the lab-frame buffer multifabs so it can be visualized as
      *  a single plotfile
@@ -356,6 +386,7 @@ private:
     void ClearParticleBuffer(int i_buffer);
     /** Redistributes particles to the buffer box array in the lab-frame */
     void RedistributeParticleBuffer (const int i_buffer);
+    void UpdateVarnamesForRZopenPMD();
 
 };
 #endif // WARPX_BTDIAGNOSTICS_H_