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stencil-mpi-nb.c
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#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <mpi.h>
const char* version_name = "A mpi comp-comm overlapped";
#include "common.h"
#ifndef SET_Y_SIZE
#define SET_Y_SIZE 8
#endif
#ifndef SET_X_SIZE
#define SET_X_SIZE 256
#endif
#define MIN(a,b) ((a) < (b) ? (a) : (b))
#define MAX(a,b) ((a) > (b) ? (a) : (b))
MPI_Comm cart_comm;
int cart_ids[2];
// 6 2 5
// y(1)
// ^ 3 0 1
// |
// | 7 4 8
// ------> z (0)
int oppo_idx[9] = {0, 3, 4, 1, 2, 7, 8, 5, 6};
int ngbs[9];
MPI_Datatype send_subarray[9], recv_subarray[9];
static int ih_z_beg[9], ih_z_end[9], ih_y_beg[9], ih_y_end[9];
// 创建分布式网格：可以根据7点或27点类型做不同的划分
void create_dist_grid(dist_grid_info_t *grid_info, int stencil_type) {
// 二维划分 沿zy轴切
int sqr_root = 1;
int num_proc_y, num_proc_z;
while (sqr_root*sqr_root < grid_info->p_num) sqr_root++;
if (sqr_root*sqr_root == grid_info->p_num) {
num_proc_z = num_proc_y = sqr_root;
} else {
int tmp = 1;
while (grid_info->p_num%tmp==0 && grid_info->p_num/tmp>tmp) tmp *= 2;
num_proc_z = grid_info->p_num / tmp;//跳出while时tmp>sqrt(p_num)
num_proc_y = tmp;
// num_proc_z = tmp;
// num_proc_y = grid_info->p_num / tmp;
}
if (grid_info->p_id == 0)
printf(" 2D partition: num_proc_y: %d, num_proc_z:%d\n", num_proc_y, num_proc_z);
// x轴不切
grid_info->local_size_x = grid_info->global_size_x;
// y轴
if (grid_info->global_size_y % num_proc_y != 0) {
if (grid_info->p_id == 0)
printf(" Error: %d cannot divide %d!\n", grid_info->global_size_y, num_proc_y);
MPI_Abort(MPI_COMM_WORLD, 1);
}
grid_info->local_size_y = grid_info->global_size_y / num_proc_y;
// z轴
if (grid_info->global_size_z % num_proc_z != 0) {
if (grid_info->p_id == 0)
printf(" Error: %d cannot divide %d!\n", grid_info->global_size_z, num_proc_z);
MPI_Abort(MPI_COMM_WORLD, 1);
}
grid_info->local_size_z = grid_info->global_size_z / num_proc_z;
// printf("pid: %d global: %d %d %d local : %d %d %d offset: %d %d %d\n", grid_info->p_id,\
// grid_info->global_size_z, grid_info->global_size_y, grid_info->global_size_x,\
// grid_info->local_size_z, grid_info->local_size_y, grid_info->local_size_x,\
// grid_info->offset_z, grid_info->offset_y, grid_info->offset_x);
// 创建通信的拓扑
ngbs[0] = grid_info->p_id;
int dims[2] = {num_proc_z, num_proc_y};
int periods[2] = {0, 0};
MPI_Cart_create(MPI_COMM_WORLD, 2, dims, &periods, 0, &cart_comm);
MPI_Cart_shift(cart_comm, 0, 1, &ngbs[3], &ngbs[1]);
MPI_Cart_shift(cart_comm, 1, 1, &ngbs[4], &ngbs[2]);
int dist_y = 1;
if (ngbs[1]==MPI_PROC_NULL || ngbs[2]==MPI_PROC_NULL) ngbs[5] = MPI_PROC_NULL;
else ngbs[5] = ngbs[1] + dist_y;
if (ngbs[1]==MPI_PROC_NULL || ngbs[4]==MPI_PROC_NULL) ngbs[8] = MPI_PROC_NULL;
else ngbs[8] = ngbs[1] - dist_y;
if (ngbs[2]==MPI_PROC_NULL || ngbs[3]==MPI_PROC_NULL) ngbs[6] = MPI_PROC_NULL;
else ngbs[6] = ngbs[3] + dist_y;
if (ngbs[3]==MPI_PROC_NULL || ngbs[4]==MPI_PROC_NULL) ngbs[7] = MPI_PROC_NULL;
else ngbs[7] = ngbs[3] - dist_y;
MPI_Cart_coords(cart_comm, grid_info->p_id, 2, &cart_ids);
grid_info->offset_x = 0;
grid_info->offset_y = grid_info->local_size_y * cart_ids[1];
grid_info->offset_z = grid_info->local_size_z * cart_ids[0];
grid_info->halo_size_x = 1;
grid_info->halo_size_y = 1;
grid_info->halo_size_z = 1;
// printf("pid: %d cart_id[0]: %d cart_id[1]: %d\n %d %d %d %d %d %d %d %d %d\n offset_y:%d offset_z:%d\n", grid_info->p_id, cart_ids[0], cart_ids[1],\
// ngbs[0],ngbs[1],ngbs[2],ngbs[3],ngbs[4],ngbs[5],ngbs[6],ngbs[7],ngbs[8], grid_info->offset_y, grid_info->offset_z);
// 创建subarray
int size[3] = { grid_info->local_size_z + 2*grid_info->halo_size_z,\
grid_info->local_size_y + 2*grid_info->halo_size_y,\
grid_info->local_size_x + 2*grid_info->halo_size_x};
int subsize[3], send_start[3], recv_start[3];
for (int i = 1; i <= 8; i++) {
switch (i) {
case 1:
subsize[0] = grid_info->halo_size_z;
subsize[1] = grid_info->local_size_y;// 注意是local_size 不带halo_width
break;
case 2:
subsize[0] = grid_info->local_size_z;
subsize[1] = grid_info->halo_size_y;
break;
case 3:
subsize[0] = grid_info->halo_size_z;
subsize[1] = grid_info->local_size_y;
break;
case 4:
subsize[0] = grid_info->local_size_z;
subsize[1] = grid_info->halo_size_y;
break;
default:// 5,6,7,8
subsize[0] = grid_info->halo_size_z;
subsize[1] = grid_info->halo_size_y;
break;
}
subsize[2] = grid_info->local_size_x + 2*grid_info->halo_size_x;
switch (i) {
case 1:// up_z
send_start[0] = grid_info->local_size_z; send_start[1] = grid_info->halo_size_y; send_start[2] = 0;
recv_start[0] = grid_info->local_size_z + grid_info->halo_size_z; recv_start[1] = grid_info->halo_size_y; recv_start[2] = 0;
break;
case 3:// down_z
send_start[0] = grid_info->halo_size_z; send_start[1] = grid_info->halo_size_y; send_start[2] = 0;
recv_start[0] = 0; recv_start[1] = grid_info->halo_size_y; recv_start[2] = 0;
break;
case 2:// up_y
send_start[0] = grid_info->halo_size_z; send_start[1] = grid_info->local_size_y; send_start[2] = 0;
recv_start[0] = grid_info->halo_size_z; recv_start[1] = grid_info->local_size_y + grid_info->halo_size_y; recv_start[2] = 0;
break;
case 4:// down_y
send_start[0] = grid_info->halo_size_z; send_start[1] = grid_info->halo_size_y; send_start[2] = 0;
recv_start[0] = grid_info->halo_size_z; recv_start[1] = 0; recv_start[2] = 0;
break;
case 5:// up_z_up_y
send_start[0] = grid_info->local_size_z; send_start[1] = grid_info->local_size_y; send_start[2] = 0;
recv_start[0] = grid_info->local_size_z + grid_info->halo_size_z; recv_start[1] = grid_info->local_size_y + grid_info->halo_size_y; recv_start[2] = 0;
break;
case 6:// down_z_up_y
send_start[0] = grid_info->halo_size_z; send_start[1] = grid_info->local_size_y; send_start[2] = 0;
recv_start[0] = 0; recv_start[1] = grid_info->local_size_y + grid_info->halo_size_y; recv_start[2] = 0;
break;
case 7:// down_z_down_y
send_start[0] = grid_info->halo_size_z; send_start[1] = grid_info->halo_size_y; send_start[2] = 0;
recv_start[0] = 0; recv_start[1] = 0; recv_start[2] = 0;
break;
case 8:// up_z_down_y
send_start[0] = grid_info->local_size_z; send_start[1] = grid_info->halo_size_y; send_start[2] = 0;
recv_start[0] = grid_info->local_size_z + grid_info->halo_size_z; recv_start[1] = 0; recv_start[2] = 0;
break;
default:
break;
}
MPI_Type_create_subarray(3, size, subsize, send_start, MPI_ORDER_C, DATA_TYPE, &send_subarray[i]);
MPI_Type_commit(&send_subarray[i]);
MPI_Type_create_subarray(3, size, subsize, recv_start, MPI_ORDER_C, DATA_TYPE, &recv_subarray[i]);
MPI_Type_commit(&recv_subarray[i]);
}
// 记录计算通信重叠部分的内halo区(注意这是内halo！)
for (int dir = 1; dir <= 4; dir++) {
//
// ----------------------------
// | 2 | |
// |--------------------| |
// | | | |
// | | | 1 |
// | | | |
// y | 3 | | |
// ^ | | | |
// | | |--------------------|
// | | | 4 |
// | ----------------------------
// O----> z
switch (dir) {
case 1:
ih_z_beg[dir] = grid_info->local_size_z;
ih_z_end[dir] = grid_info->halo_size_z + grid_info->local_size_z;
ih_y_beg[dir] = grid_info->halo_size_y * 2;
ih_y_end[dir] = grid_info->halo_size_y + grid_info->local_size_y;
break;
case 2:
ih_z_beg[dir] = grid_info->halo_size_z;
ih_z_end[dir] = grid_info->local_size_z;
ih_y_beg[dir] = grid_info->local_size_y;
ih_y_end[dir] = ih_y_beg[dir] + grid_info->halo_size_y;
break;
case 3:
ih_z_beg[dir] = grid_info->halo_size_z;
ih_z_end[dir] = grid_info->halo_size_z * 2;
ih_y_beg[dir] = grid_info->halo_size_y;
ih_y_end[dir] = grid_info->local_size_y;
break;
case 4:
ih_z_beg[dir] = grid_info->halo_size_z * 2;
ih_z_end[dir] = grid_info->halo_size_z + grid_info->local_size_z;
ih_y_beg[dir] = grid_info->halo_size_y;
ih_y_end[dir] = grid_info->halo_size_y * 2;
break;
default:
break;
}
// printf("pid %d, dir %d, %d %d %d %d\n", grid_info->p_id, dir, ih_z_beg[dir], ih_z_end[dir], ih_y_beg[dir], ih_y_end[dir]);
}
}
void destroy_dist_grid(dist_grid_info_t *grid_info) {
for (int i = 1; i <= 8; i++) {
if (send_subarray[i] != MPI_DATATYPE_NULL)
MPI_Type_free(&send_subarray[i]);
if (recv_subarray[i] != MPI_DATATYPE_NULL)
MPI_Type_free(&recv_subarray[i]);
}
}
ptr_t stencil_7(ptr_t grid, ptr_t aux, const dist_grid_info_t *grid_info, int nt, double * calc_time, double * comm_time) {
ptr_t buffer[2] = {grid, aux};
int x_start = grid_info->halo_size_x, x_end = grid_info->local_size_x + grid_info->halo_size_x;
int y_start = grid_info->halo_size_y, y_end = grid_info->local_size_y + grid_info->halo_size_y;
int z_start = grid_info->halo_size_z, z_end = grid_info->local_size_z + grid_info->halo_size_z;
int ldx = grid_info->local_size_x + 2 * grid_info->halo_size_x;
int ldy = grid_info->local_size_y + 2 * grid_info->halo_size_y;
int ldz = grid_info->local_size_z + 2 * grid_info->halo_size_z;
MPI_Request req_send[4], req_recv[4];
MPI_Status status[4];
// for boundary conditions
for (int i = 1; i <= 4; i++) {// 7点stencil只需要通信4个
int oppo = oppo_idx[i];
MPI_Sendrecv(buffer[0], 1, send_subarray[i] , ngbs[i] , grid_info->p_id ^ ngbs[i] ,\
buffer[0], 1, recv_subarray[oppo], ngbs[oppo], grid_info->p_id ^ ngbs[oppo], cart_comm, &status[i-1]);
}
// y_start += grid_info->halo_size_y; y_end -= grid_info->halo_size_y;
// z_start += grid_info->halo_size_z; z_end -= grid_info->halo_size_z;
for(int t = 0; t < nt; ++t) {
cptr_t a0 = buffer[t % 2];
ptr_t a1 = buffer[(t + 1) % 2];
// 先计算内halo区
for (int dir = 1; dir <= 4; dir++) {
ptr_t a1_local = a1 + ih_z_beg[dir]*ldx*ldy + ih_y_beg[dir]*ldx;
cptr_t a0_local_Z = a0 + (a1_local - a1);
cptr_t a0_local_P = a0_local_Z + ldy*ldx;
cptr_t a0_local_N = a0_local_Z - ldy*ldx;
int yy_end = ih_y_end[dir]-ih_y_beg[dir];
for (int z = ih_z_beg[dir]; z < ih_z_end[dir]; z++){
for (int y = 0; y < yy_end; y++)
for (int x = x_start; x < x_end; x++)
a1_local[y*ldx+x] \
= ALPHA_ZZZ * a0_local_Z[y*ldx+x]\
+ ALPHA_NZZ * a0_local_Z[y*ldx+x-1] \
+ ALPHA_PZZ * a0_local_Z[y*ldx+x+1] \
+ ALPHA_ZNZ * a0_local_Z[(y-1)*ldx+x] \
+ ALPHA_ZPZ * a0_local_Z[(y+1)*ldx+x] \
+ ALPHA_ZZN * a0_local_N[y*ldx+x] \
+ ALPHA_ZZP * a0_local_P[y*ldx+x];
a1_local = a1_local + ldx*ldy;
a0_local_N = a0_local_Z;
a0_local_Z = a0_local_P;
a0_local_P = a0_local_P + ldx*ldy;
}
}
// 隐藏非阻塞通信
for (int dir = 1; dir <= 4; dir++) {
int oppo = oppo_idx[dir];
MPI_Isend(a1, 1, send_subarray[dir], ngbs[dir], grid_info->p_id ^ ngbs[dir], cart_comm, &req_send[dir-1]);
MPI_Irecv(a1, 1, recv_subarray[oppo], ngbs[oppo], grid_info->p_id ^ ngbs[oppo], cart_comm, &req_recv[oppo-1]);
}
for (int JJ = y_start; JJ < y_end; JJ += SET_Y_SIZE) {
for (int II = x_start; II < x_end; II += SET_X_SIZE){
int REAL_Y_SIZE = MIN(SET_Y_SIZE, y_end - JJ);
int REAL_X_SIZE = MIN(SET_X_SIZE, x_end - II);
ptr_t a1_local = a1 + z_start*ldx*ldy + JJ*ldx + II;
cptr_t a0_local_Z = a0 + (a1_local - a1);
cptr_t a0_local_P = a0_local_Z + ldy*ldx;
cptr_t a0_local_N = a0_local_Z - ldy*ldx;
for(int z = z_start; z < z_end; ++z) {
for(int y = 0; y < REAL_Y_SIZE; y++) {
#pragma unroll
for(int x = 0; x < REAL_X_SIZE; x++) {
a1_local[y*ldx+x] \
= ALPHA_ZZZ * a0_local_Z[y*ldx+x]\
+ ALPHA_NZZ * a0_local_Z[y*ldx+x-1] \
+ ALPHA_PZZ * a0_local_Z[y*ldx+x+1] \
+ ALPHA_ZNZ * a0_local_Z[(y-1)*ldx+x] \
+ ALPHA_ZPZ * a0_local_Z[(y+1)*ldx+x] \
+ ALPHA_ZZN * a0_local_N[y*ldx+x] \
+ ALPHA_ZZP * a0_local_P[y*ldx+x];
}// x loop
}// y loop
a1_local = a1_local + ldx*ldy;
a0_local_N = a0_local_Z;
a0_local_Z = a0_local_P;
a0_local_P = a0_local_P + ldx*ldy;
}// z loop
}
}
MPI_Waitall(4, req_recv, status);
MPI_Waitall(4, req_send, status);
}
return buffer[nt % 2];
}
ptr_t stencil_27(ptr_t grid, ptr_t aux, const dist_grid_info_t *grid_info, int nt, double * calc_time, double * comm_time) {
ptr_t buffer[2] = {grid, aux};
int x_start = grid_info->halo_size_x, x_end = grid_info->local_size_x + grid_info->halo_size_x;
int y_start = grid_info->halo_size_y, y_end = grid_info->local_size_y + grid_info->halo_size_y;
int z_start = grid_info->halo_size_z, z_end = grid_info->local_size_z + grid_info->halo_size_z;
int ldx = grid_info->local_size_x + 2 * grid_info->halo_size_x;
int ldy = grid_info->local_size_y + 2 * grid_info->halo_size_y;
int ldz = grid_info->local_size_z + 2 * grid_info->halo_size_z;
MPI_Request req_send[8], req_recv[8];
MPI_Status status[8];
// for boundary conditions
for (int i = 1; i <= 8; i++) {// 27点stencil需要通信8个
int oppo = oppo_idx[i];
MPI_Sendrecv(buffer[0], 1, send_subarray[i] , ngbs[i] , grid_info->p_id ^ ngbs[i] ,\
buffer[0], 1, recv_subarray[oppo], ngbs[oppo], grid_info->p_id ^ ngbs[oppo], cart_comm, &status[i-1]);
}
// 刨去外周一圈，导致对不齐（或者别的原因？），速度骤降，比重新再多算一遍外周还慢得多！！！
// y_start += grid_info->halo_size_y; y_end -= grid_info->halo_size_y;
// z_start += grid_info->halo_size_z; z_end -= grid_info->halo_size_z;
for(int t = 0; t < nt; ++t) {
cptr_t a0 = buffer[t % 2];
ptr_t a1 = buffer[(t + 1) % 2];
// 先计算内halo区
for (int dir = 1; dir <= 4; dir++) {
ptr_t a1_local = a1 + ih_z_beg[dir]*ldx*ldy + ih_y_beg[dir]*ldx;
cptr_t a0_local_Z = a0 + (a1_local - a1);
cptr_t a0_local_P = a0_local_Z + ldy*ldx;
cptr_t a0_local_N = a0_local_Z - ldy*ldx;
int yy_end = ih_y_end[dir]-ih_y_beg[dir];
for (int z = ih_z_beg[dir]; z < ih_z_end[dir]; z++){
for (int y = 0; y < yy_end; y++)
for (int x = x_start; x < x_end; x++)
a1_local[y*ldx+x] \
= ALPHA_ZZZ * a0_local_Z[y*ldx+x] \
+ ALPHA_NZZ * a0_local_Z[y*ldx+x-1] \
+ ALPHA_PZZ * a0_local_Z[y*ldx+x+1] \
+ ALPHA_ZNZ * a0_local_Z[(y-1)*ldx+x] \
+ ALPHA_ZPZ * a0_local_Z[(y+1)*ldx+x] \
+ ALPHA_ZZN * a0_local_N[y*ldx+x] \
+ ALPHA_ZZP * a0_local_P[y*ldx+x] \
+ ALPHA_NNZ * a0_local_Z[(y-1)*ldx+x-1] \
+ ALPHA_PNZ * a0_local_Z[(y-1)*ldx+x+1] \
+ ALPHA_NPZ * a0_local_Z[(y+1)*ldx+x-1] \
+ ALPHA_PPZ * a0_local_Z[(y+1)*ldx+x+1] \
+ ALPHA_NZN * a0_local_N[y*ldx+x-1] \
+ ALPHA_PZN * a0_local_N[y*ldx+x+1] \
+ ALPHA_NZP * a0_local_P[y*ldx+x-1] \
+ ALPHA_PZP * a0_local_P[y*ldx+x+1] \
+ ALPHA_ZNN * a0_local_N[(y-1)*ldx+x] \
+ ALPHA_ZPN * a0_local_N[(y+1)*ldx+x] \
+ ALPHA_ZNP * a0_local_P[(y-1)*ldx+x] \
+ ALPHA_ZPP * a0_local_P[(y+1)*ldx+x] \
+ ALPHA_NNN * a0_local_N[(y-1)*ldx+x-1] \
+ ALPHA_PNN * a0_local_N[(y-1)*ldx+x+1] \
+ ALPHA_NPN * a0_local_N[(y+1)*ldx+x-1] \
+ ALPHA_PPN * a0_local_N[(y+1)*ldx+x+1] \
+ ALPHA_NNP * a0_local_P[(y-1)*ldx+x-1] \
+ ALPHA_PNP * a0_local_P[(y-1)*ldx+x+1] \
+ ALPHA_NPP * a0_local_P[(y+1)*ldx+x-1] \
+ ALPHA_PPP * a0_local_P[(y+1)*ldx+x+1];
a1_local = a1_local + ldx*ldy;
a0_local_N = a0_local_Z;
a0_local_Z = a0_local_P;
a0_local_P = a0_local_P + ldx*ldy;
}
}
// 隐藏非阻塞通信
for (int dir = 1; dir <= 8; dir++) {
int oppo = oppo_idx[dir];
MPI_Isend(a1, 1, send_subarray[dir], ngbs[dir], grid_info->p_id ^ ngbs[dir], cart_comm, &req_send[dir-1]);
MPI_Irecv(a1, 1, recv_subarray[oppo], ngbs[oppo], grid_info->p_id ^ ngbs[oppo], cart_comm, &req_recv[oppo-1]);
}
for (int JJ = y_start; JJ < y_end; JJ += SET_Y_SIZE) {
for (int II = x_start; II < x_end; II += SET_X_SIZE){
int REAL_Y_SIZE = MIN(SET_Y_SIZE, y_end - JJ);
int REAL_X_SIZE = MIN(SET_X_SIZE, x_end - II);
ptr_t a1_local = a1 + z_start*ldx*ldy + JJ*ldx + II;
cptr_t a0_local_Z = a0 + (a1_local - a1);
cptr_t a0_local_P = a0_local_Z + ldy*ldx;
cptr_t a0_local_N = a0_local_Z - ldy*ldx;
for(int z = z_start; z < z_end; ++z) {
for(int y = 0; y < REAL_Y_SIZE; y++) {
#pragma unroll
for(int x = 0; x < REAL_X_SIZE; x++) {
a1_local[y*ldx+x] \
= ALPHA_ZZZ * a0_local_Z[y*ldx+x] \
+ ALPHA_NZZ * a0_local_Z[y*ldx+x-1] \
+ ALPHA_PZZ * a0_local_Z[y*ldx+x+1] \
+ ALPHA_ZNZ * a0_local_Z[(y-1)*ldx+x] \
+ ALPHA_ZPZ * a0_local_Z[(y+1)*ldx+x] \
+ ALPHA_ZZN * a0_local_N[y*ldx+x] \
+ ALPHA_ZZP * a0_local_P[y*ldx+x] \
+ ALPHA_NNZ * a0_local_Z[(y-1)*ldx+x-1] \
+ ALPHA_PNZ * a0_local_Z[(y-1)*ldx+x+1] \
+ ALPHA_NPZ * a0_local_Z[(y+1)*ldx+x-1] \
+ ALPHA_PPZ * a0_local_Z[(y+1)*ldx+x+1] \
+ ALPHA_NZN * a0_local_N[y*ldx+x-1] \
+ ALPHA_PZN * a0_local_N[y*ldx+x+1] \
+ ALPHA_NZP * a0_local_P[y*ldx+x-1] \
+ ALPHA_PZP * a0_local_P[y*ldx+x+1] \
+ ALPHA_ZNN * a0_local_N[(y-1)*ldx+x] \
+ ALPHA_ZPN * a0_local_N[(y+1)*ldx+x] \
+ ALPHA_ZNP * a0_local_P[(y-1)*ldx+x] \
+ ALPHA_ZPP * a0_local_P[(y+1)*ldx+x] \
+ ALPHA_NNN * a0_local_N[(y-1)*ldx+x-1] \
+ ALPHA_PNN * a0_local_N[(y-1)*ldx+x+1] \
+ ALPHA_NPN * a0_local_N[(y+1)*ldx+x-1] \
+ ALPHA_PPN * a0_local_N[(y+1)*ldx+x+1] \
+ ALPHA_NNP * a0_local_P[(y-1)*ldx+x-1] \
+ ALPHA_PNP * a0_local_P[(y-1)*ldx+x+1] \
+ ALPHA_NPP * a0_local_P[(y+1)*ldx+x-1] \
+ ALPHA_PPP * a0_local_P[(y+1)*ldx+x+1];
}// x
}// y
a1_local = a1_local + ldx*ldy;
a0_local_N = a0_local_Z;
a0_local_Z = a0_local_P;
a0_local_P = a0_local_P + ldx*ldy;
}// z
}
}
MPI_Waitall(8, req_recv, status);
MPI_Waitall(8, req_send, status);
}
return buffer[nt % 2];
}