D05_phi1d_to_phi3d

模块定位

D05_phi1d_to_phi3d 是 Poisson 求解与电场计算之间的衔接步骤。 HYPRE 返回的 1D 解向量 phi1d 按照 i 最快、k 最慢的存储顺序逐元素写入 3D ghost-cell 数组 phi3d，随后通过 MPI 点对点通信填充相邻 rank 的 ghost 层；对单 rank 方向且域长度大于零的情形，则直接做周期环绕填充。调用完成后，物理边界上的非周期、非 MPI ghost 格保持为零，调用方需在此之后（且在调用 D06 之前）按实际边界条件另行赋值。

文件角色
文件	角色
mod_D05_phi1d_to_phi3d.f90	模块包装文件，集中 include D05 子程序。
sub_D05_phi1d_to_phi3d.f90	主子程序：1D→3D 解包 + 周期 BC + MPI halo 交换。
`inc_exchange_in_x/y/z.f90`	在主子程序内 include 的代码片段，分别实现三个 Cartesian 方向的 MPI ghost 交换；依赖 `inc_send_recv.f90` 与 `inc_recv_send.f90`。
`inc_send_recv.f90`	先发后收的 MPI 点对点模式（奇逻辑索引 rank 使用）。
`inc_recv_send.f90`	先收后发的 MPI 点对点模式（偶逻辑索引 rank 使用）。

ghost cell 约定

D05 交换的是 边界格本身：每个 rank 把自身 iu(d) 方向末端格发给右邻 rank 的 ghost 格，把 il(d) 方向首端格发给左邻 rank 的 ghost 格。这与 H01 电场交换（使用次边界格）的约定不同，调用方需注意区分。

调用顺序建议

调用 D01–D04 中的 HYPRE 求解器，得到 phi1d。
调用 sub_D05_phi1d_to_phi3d 解包并交换 ghost。
对物理边界的非周期 ghost 格按 Dirichlet/Neumann 等条件赋值。
调用 sub_D06_phi_to_E 计算电场。

Module Role

D05_phi1d_to_phi3d bridges the HYPRE Poisson solve and the electric-field computation. The 1D solution vector phi1d (loop order: i fastest, k slowest) is unpacked element by element into the physical domain of the 3D ghost-cell array phi3d. Ghost cells are then filled either by periodic wrap-around (when the MPI split in that direction is 1 and the domain length is positive) or by point-to-point MPI communication with neighbouring ranks. After the call, non-periodic, non-MPI ghost cells at physical boundaries remain zero; the caller must set them according to the actual boundary conditions before calling D06.

File Roles
File	Role
mod_D05_phi1d_to_phi3d.f90	Module wrapper collecting the D05 subroutine.
sub_D05_phi1d_to_phi3d.f90	Main subroutine: 1D→3D unpack, periodic BC fill, and MPI halo exchange.
`inc_exchange_in_x/y/z.f90`	Code fragments included inside the main subroutine implementing MPI ghost exchange in each Cartesian direction; depend on `inc_send_recv.f90` and `inc_recv_send.f90`.
`inc_send_recv.f90`	Send-then-receive MPI point-to-point pattern used by odd-index ranks.
`inc_recv_send.f90`	Receive-then-send MPI point-to-point pattern used by even-index ranks.

Ghost Cell Convention

D05 exchanges boundary cells: each rank sends its iu(d)-end cell to the right neighbour’s ghost slot, and its il(d)-end cell to the left neighbour’s ghost slot. This differs from the H01 electric-field exchange, which uses the second-from-boundary cell; callers must not confuse the two conventions.

Recommended Call Order

Run the HYPRE solver from D01–D04 to obtain phi1d.
Call sub_D05_phi1d_to_phi3d to unpack and exchange ghost cells.
Set non-periodic physical-boundary ghost cells (Dirichlet, Neumann, etc.).
Call sub_D06_phi_to_E to compute the electric field.