Overview

This PR refactors multiple physics and IO modules to replace direct MPI_Allreduce calls (particularly those using MPI_IN_PLACE) with the encapsulated templated API in Parallel_Reduce. This improves code consistency across the repository and ensures that MPI operations are handled through a unified interface.

Key Changes

• Encapsulation of MPI calls: Replaced manual MPI_Allreduce with Parallel_Reduce::reduce_all and Parallel_Reduce::reduce_pool.
• Modules Updated:
  • K-Points: source/source_cell/parallel_kpoints.cpp
  • IO/Log: source/source_io/output_log.cpp
  • PW Solver: source/source_pw/module_pwdft/VNL_in_pw.cpp and source/source_pw/module_pwdft/elecond.cpp
  • Stochastic DFT: source/source_pw/module_stodft/sto_dos.cpp, source/source_pw/module_stodft/sto_elecond.cpp, and source/source_pw/module_stodft/sto_iter.cpp

Benefits

• Better Abstraction: Centralizes parallel reduction logic, making the code cleaner and easier to maintain.
• Safety: Utilizes the library's internal status checks for MPI initialization, preventing potential crashes in serial/uninitialized environments.
• Consistency: Aligning various modules with the standard ABACUS parallel communication pattern.