Refactor DFT+U occupation reader for strict compact input

source/Makefile.Objects

@@ -952,6 +952,7 @@ OBJS_SRCPW=h_ewald_pw.o\
     update_cell_pw.o\
     dftu_base.o\
     dftu_base_io.o\
+    dftu_base_io_read.o\
     dftu_pw.o\
     dftu_pw_tools.o\
     yukawa_screening.o\

source/source_io/module_parameter/read_inp_exx_dftu.cpp

@@ -816,7 +816,7 @@ void ReadInput::item_dftu()
 * 1: The first SCF step will use an initial density matrix read from a file, but for later steps, the onsite density matrix will be updated.
 * 2: The same onsite density matrix read from the file will be used throughout the entire calculation.
 
-[NOTE] The occupation-matrix file is read from the directory specified by read_file_dir. The search order is dm_onsite_ini.txt -> occ_mat.txt -> dm_onsite.txt, so a previously output occ_mat.txt can be reused directly without renaming. The easiest way to obtain such a file is to run a DFT+U calculation with out_occ_mat=1 (the default); the resulting occ_mat.txt in the OUT.prefix directory (which always holds the occupation matrix of the latest electronic step) can be placed in read_file_dir as-is. When out_freq_ion is positive, separate occ_matg{geom_step}.txt files are also written, one per output ionic step; they may contain several electronic-step sections separated by comment headers. The format of the file is rather straight-forward.)";
+[NOTE] The occupation-matrix file is read from the directory specified by read_file_dir. The search order is dm_onsite_ini.txt -> occ_mat.txt. Input must use the current compact format written by ABACUS; legacy Atom=/L=/spin= files such as dm_onsite.txt are not supported. The easiest way to obtain a valid file is to run a DFT+U calculation with out_occ_mat=1 (the default); the resulting occ_mat.txt in the OUT.prefix directory (which always holds the occupation matrix of the latest electronic step) can be placed in read_file_dir as-is. When out_freq_ion is positive, separate occ_matg{geom_step}.txt files are also written, one per output ionic step; they may contain several electronic-step sections separated by comment headers.)";
         item.default_value = "0";
         item.unit = "";
         read_sync_int(input.init_occ_mat);

source/source_lcao/module_dftu/unittests/CMakeLists.txt

@@ -91,6 +91,7 @@ AddTest(
   ../../../source_estate/module_dm/dmr_full.cpp
   ../../../source_pw/module_pwdft/dftu_base.cpp
   ../../../source_pw/module_pwdft/dftu_base_io.cpp
+  ../../../source_pw/module_pwdft/dftu_base_io_read.cpp
   ../../../source_pw/module_pwdft/yukawa_screening.cpp
   ../../../source_estate/occ_matrix.cpp
   ../../../source_estate/occ_mixer.cpp
@@ -136,6 +137,7 @@ AddTest(
   ../../../source_estate/module_dm/dmr_full.cpp
   ../../../source_pw/module_pwdft/dftu_base.cpp
   ../../../source_pw/module_pwdft/dftu_base_io.cpp
+  ../../../source_pw/module_pwdft/dftu_base_io_read.cpp
   ../../../source_pw/module_pwdft/yukawa_screening.cpp
   ../../../source_estate/occ_matrix.cpp
   ../../../source_estate/occ_mixer.cpp

source/source_pw/module_pwdft/CMakeLists.txt

@@ -31,6 +31,7 @@ endif()
 list(APPEND objects
     dftu_base.cpp
     dftu_base_io.cpp
+    dftu_base_io_read.cpp
     dftu_pw.cpp
     dftu_pw_tools.cpp
     yukawa_screening.cpp

source/source_pw/module_pwdft/dftu_base.cpp

@@ -169,21 +169,20 @@ void Plus_U_Base::init_base(UnitCell& cell,
         else
         {
             // Try the user-prepared dm_onsite_ini.txt first, then fall back to
-            // the occupation-matrix snapshot written by a previous run
-            // (occ_mat.txt), and finally to the legacy dm_onsite.txt name.
+            // the compact occupation-matrix snapshot written by a previous
+            // run (occ_mat.txt). Legacy dm_onsite.txt input is not supported.
             const std::vector<std::string> candidates = {"dm_onsite_ini.txt",
-                                                          "occ_mat.txt",
-                                                          "dm_onsite.txt"};
+                                                          "occ_mat.txt"};
             const std::string readin_fn = DFTU_BASE::find_first_existing_file(global_readin_dir, candidates);
             if (readin_fn.empty())
             {
                 ModuleBase::WARNING_QUIT("Plus_U_Base::init_base",
                                          "init_occ_mat is set but no occupation-matrix file found in "
                                          + global_readin_dir
-                                         + ". Tried: dm_onsite_ini.txt, occ_mat.txt, dm_onsite.txt");
+                                         + ". Tried: dm_onsite_ini.txt, occ_mat.txt");
             }
-            DFTU_BASE::read_occup_m(cell, this->occmat_, this->l_channel, this->init_occ_mat,
-                                    readin_fn, init_chg, nspin, npol, soc_layout);
+            DFTU_BASE::read_occup_m(cell, this->occmat_, this->l_channel,
+                                    readin_fn, nspin, npol, soc_layout);
 #ifdef __MPI
             DFTU_BASE::local_occup_bcast(cell, this->occmat_, this->l_channel, nspin, npol);
 #endif
@@ -202,22 +201,20 @@ void Plus_U_Base::init_base(UnitCell& cell,
     {
         if (init_chg == "file")
         {
-            // occ_mat.txt is the current output name; fall back to the
-            // legacy dm_onsite.txt so that output directories written by
-            // older versions can still be used for restarts.
-            const std::vector<std::string> candidates = {"occ_mat.txt", "dm_onsite.txt"};
+            // Only the current compact restart output is supported.
+            const std::vector<std::string> candidates = {"occ_mat.txt"};
             const std::string readin_fn = DFTU_BASE::find_first_existing_file(global_readin_dir, candidates);
             if (readin_fn.empty())
             {
                 ModuleBase::WARNING_QUIT("Plus_U_Base::init_base",
                                          "init_chg is set to file but no occupation-matrix file "
                                          "found in "
                                          + global_readin_dir
-                                         + ". Tried: occ_mat.txt, dm_onsite.txt. Please do an scf "
+                                         + ". Tried: occ_mat.txt. Please do an scf "
                                            "calculation first.");
             }
-            DFTU_BASE::read_occup_m(cell, this->occmat_, this->l_channel, this->init_occ_mat,
-                                    readin_fn, init_chg, nspin, npol, soc_layout);
+            DFTU_BASE::read_occup_m(cell, this->occmat_, this->l_channel,
+                                    readin_fn, nspin, npol, soc_layout);
 #ifdef __MPI
             DFTU_BASE::local_occup_bcast(cell, this->occmat_, this->l_channel, nspin, npol);
 #endif