fix: turn on kpar in tests; add guard for EXX+kpar

Author: maki49

source/source_io/module_parameter/input_conv.cpp

@@ -256,6 +256,14 @@ void Input_Conv::Convert()
         ModuleBase::WARNING_QUIT("Input_Conv", "EXX stress is not supported for basis_type = lcao_in_pw");
     }
 
+    if (cal_exx && inp.basis_type == "lcao" && inp.kpar != 1)
+    {
+        // module_ri's real-space D(R)/Ds construction (RI_2D_Comm::split_m2D_ktoR_k) only
+        // sums each pool's local k-points, with no reduce_pool/reduce_all afterwards, so
+        // E_exx/H_exx(R)/forces would silently be built from a single pool's k-points.
+        ModuleBase::WARNING_QUIT("Input_Conv", "EXX (basis_type = lcao) does not support k-point parallelism (kpar > 1)");
+    }
+
     //----------------------------------------------------------
     // reset symmetry flag to avoid error
     //----------------------------------------------------------

source/source_lcao/module_dftu/dftu_nao_occ.cpp

@@ -101,6 +101,9 @@ void DFTU_LCAO::cal_occ_mat_k(const Parallel_Orbitals* pv,
     // (symmetry) when crystal symmetry reduces the k-mesh, each ik below is only
     // the irreducible representative; build the AO rotation machinery once so
     // its k-star can be correctly re-expanded (see accumulate_occ_over_kstar).
+    // Symmetry is analyzed once at the beginning and preserved by symmetrization.
+    // Accordingly, symrot_, dftu_occ_symrot, and the cached Ms_ remain valid and 
+    // do not need to be rebuilt each ionic step.
     const bool dftu_spacegroup_symmetry = (ModuleSymmetry::Symmetry::symm_flag == 1) && !kv.kstars.empty();
     if (dftu_spacegroup_symmetry && !dftu_occ_symrot_built)
     {

tests/17_DS_DFTU/03_LCAO_DFTU_S2_Z/INPUT

@@ -16,6 +16,7 @@ mixing_type    broyden
 mixing_beta    0.4
 ks_solver    genelpa
 symmetry    1
+kpar        4
 
 # DFT+U parameters
 dft_plus_u    1

tests/17_DS_DFTU/03_LCAO_DFTU_S2_Z/result.ref

@@ -1,4 +1,4 @@
-etotref -6771.6902262248895568
+etotref -6771.6902262248995612
 etotperatomref -3385.8451131124
 pointgroupref C_3v
 spacegroupref C_3v

tests/17_DS_DFTU/04_LCAO_DFTU_S4_XY/INPUT

@@ -17,6 +17,7 @@ mixing_type    broyden
 mixing_beta    0.4
 ks_solver    genelpa
 symmetry    1
+kpar        4
 
 # DFT+U parameters
 dft_plus_u    1