Blame view
lab3/mpi_heat2D.c
8.06 KB
3604dfae0
MPI version
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 |
/****************************************************************************
* DESCRIPTION:
* Serial HEAT2D Example - C Version
* This example is based on a simplified
* two-dimensional heat equation domain decomposition. The initial
* temperature is computed to be high in the middle of the domain and
* zero at the boundaries. The boundaries are held at zero throughout
* the simulation. During the time-stepping, an array containing two
* domains is used; these domains alternate between old data and new data.
*
* The physical region, and the boundary conditions, are suggested
by this diagram;
u = 0
+------------------+
| |
u = 100 | | u = 100
| |
| |
| |
| |
+------------------+
u = 100
Interrior point :
u[Central] = (1/4) * ( u[North] + u[South] + u[East] + u[West] )
PARALLEL MPI VERSION :
+-------------------+
| | P0 m=(n-2)/P +2
+-------------------+
| | P1
+-------------------+
n | | ..
+-------------------+
| | Pq
+-------------------+
<-------- n -------->
<-------n-2 ------>
****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <mpi/mpi.h>
#define NN 50
#define MM 50
#define RING 100
#define ITER_PRINT 100
#define PRINT_DATA 1
#define MAX_ITER 1000
#define _EPSILON 0.01
float update(int rank,int size, int nx,int ny, float *u, float *unew);
void inidat(int rank, int size, int nx, int ny, float *u, float *unew);
void prtdat(int rank, int size, int nx, int ny, float *u,const char *fnam);
int main(int argc, char *argv[])
{
int N=NN,M=MM;
int rank,size;
float EPSILON=_EPSILON;
/* INITIALIZE MPI */
MPI_Init(&argc, &argv);
/* GET THE PROCESSOR ID AND NUMBER OF PROCESSORS */
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
//Only Rank 0 read application parameters
if(rank==0) {
if(argc !=3)
{
fprintf(stderr,"usage %s N EPSILON
", argv[0]);
fprintf(stderr,"\t\twhere N is GRID size, EPSILON is Tolerance
");
fprintf(stderr,"\t\texample N = 100, EPSILON = 0.1
");
return -1;
}
N = M = atoi(argv[1]);
EPSILON = atof(argv[2]);
if(N % size!=0)
{
fprintf(stderr,"Grid Size MUST be divisible by the number of processors !");
return -1;
}
}
//Wait for rank 0 , all process start here
MPI_Barrier(MPI_COMM_WORLD);
//Exchange N
MPI_Bcast(&N , 1, MPI_FLOAT, 0 , MPI_COMM_WORLD);
//Exchange EPSILON
MPI_Bcast(&EPSILON , 1, MPI_FLOAT, 0 , MPI_COMM_WORLD);
//local size
M = (N-2)/size + 2;
float *u = (float *)malloc(N * M * sizeof(float));
float *unew = (float *)malloc(N * M * sizeof(float));
if(u==0 || unew ==0)
{
perror("Can't allocated data
");
return -1;
}
if(rank==0) {
printf ( "
" );
printf ( "HEATED_PLATE
" );
printf ( " Parallel MPI version using %d processors
",size );
printf ( " A program to solve for the steady state temperature distribution
" );
printf ( " over a rectangular plate.
" );
printf ( "
" );
printf ( " Spatial grid of %d by %d points.
", N, N );
printf ( " Each processor will use grid of %d +2 by %d points.
", M-2, N );
printf ( " The iteration will end until tolerance <= %f
",EPSILON);
}
/* Initialize grid and create input file
* each process initialize its part
* */
inidat(rank,size,M,N,u,unew);
prtdat(rank,size,M,N,u, "initial.dat");
/*
* iterate until the new solution unew differs from the old solution u
* by no more than EPSILON.
* */
float diff=1.0;
int iter=0;
while(diff> EPSILON) {
diff= update(rank,size,M,N, u, unew);
if(rank==0)
if(iter%ITER_PRINT==0)
printf("Processor #%d, iteration %d, epsilon = %f
", rank,iter,diff);
iter++;
}
prtdat(rank,size,M,N, u, "final.dat");
free(u);
free(unew);
MPI_Finalize();
}
/****************************************************************************
* subroutine update
****************************************************************************/
float update(int rank, int size, int nx,int ny, float *u, float *unew){
int ix, iy;
float diff=0.0;
float globaldiff;
MPI_Status status;
/*
* EXCHANGE GHOST CELL
*/
if (rank > 0 && rank< size-1)
{
MPI_Sendrecv(&u[ny*(nx-2)], ny, MPI_FLOAT, rank+1, 0,
&u[ny*0], ny, MPI_FLOAT, rank-1, 0, MPI_COMM_WORLD, &status);
MPI_Sendrecv(&u[ny*1], ny, MPI_FLOAT, rank-1, 1,
&u[ny*(nx-1)], ny, MPI_FLOAT, rank+1, 1, MPI_COMM_WORLD, &status);
}
else if (rank == 0 && rank< size-1)
MPI_Sendrecv(&u[ny*(nx-2)], ny, MPI_FLOAT, rank+1, 0,
&u[ny*(nx-1)], ny, MPI_FLOAT, rank+1, 1, MPI_COMM_WORLD, &status);
else if ( rank> 0 && rank == size-1)
MPI_Sendrecv(&u[ny*1], ny, MPI_FLOAT, rank-1, 1,
&u[ny*0], ny, MPI_FLOAT, rank-1, 0, MPI_COMM_WORLD, &status);
/**
* PERFORM LOCAL COMPUTATION
* */
for (ix = 1; ix < nx-1; ix++) {
for (iy = 1; iy < ny-1; iy++) {
unew[ix*ny+iy] = (u[(ix+1)*ny+iy] + u[(ix-1)*ny+iy] + u[ix*ny+iy+1] + u[ix*ny+iy-1] )/4.0
;
if (diff < fabs (unew[ix*ny+iy] - u[ix*ny+iy] ))
{
diff = fabs ( unew[ix*ny+iy] - u[ix*ny+iy] );
}
}
}
/**
* COMPUTE GLOBAL CONVERGENCE
*
* */
MPI_Allreduce(&diff, &globaldiff , 1, MPI_FLOAT, MPI_MAX, MPI_COMM_WORLD);
/**
* COPY OLD DATA
* */
for (ix = 1; ix < nx-1; ix++) {
for (iy = 1; iy < ny-1; iy++) {
u[ix*ny+iy] = unew[ix*ny+iy];
}
}
return globaldiff;
}
/*****************************************************************************
* Initialize Data
*****************************************************************************/
void inidat(int rank, int size,int nx, int ny, float *u, float *unew)
{
int ix, iy;
/*
*Set boundary data and interrior values
* */
// interior points
for (ix = 1; ix < nx-1; ix++)
for (iy = 1; iy < ny-1; iy++) {
u[ix*ny+iy]=0.0;
}
//boundary left
for (ix = 1; ix < nx-1; ix++){
u[ix*ny]=100.0;
}
//boundary right
for (ix = 1; ix < nx-1; ix++){
u[ix*ny+ (ny-1)]=100.0;
}
//boundary down
for (iy = 0; iy < ny; iy++){
if(rank==size-1) {
u[(nx-1)*(ny)+iy]=100.0;
}else
{
u[(nx-1)*(ny)+iy]=0.0;
}
}
//boundary top
for (iy = 0; iy < ny; iy++){
u[iy]=0.0;
}
}
/***************************************************************************
* Print Data to files
**************************************************************************/
void print2file(int rank, int nx, int ny, float *u,const char *fname)
{
int ix, iy;
FILE *fp;
char str[255];
sprintf(str, "%d_%s", rank,fname);
fp = fopen(str, "w");
for (ix = 0 ; ix < nx; ix++) {
for (iy =0; iy < ny; iy++) {
fprintf(fp, "%6.2f ", u[ix*ny+iy]);
}
fputc ( '
', fp);
}
fclose(fp);
}
void prtdat(int rank, int size,int nx, int ny, float *u,const char *fname)
{
if(ITER_PRINT==0)return;
/**
* USE TOKEN RING to write to unique file
* 0 will rite first and then 1, 2, ... size-1
*
* * */
print2file(rank,nx,ny,u,fname);
}
|