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NuSiF-Solver/BasicSolver/2D-mpi-v1/src/solver.c

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/*
* Copyright (C) 2022 NHR@FAU, University Erlangen-Nuremberg.
* All rights reserved. This file is part of nusif-solver.
* Use of this source code is governed by a MIT style
* license that can be found in the LICENSE file.
*/
#include <float.h>
#include <math.h>
#include <mpi.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "allocate.h"
#include "parameter.h"
#include "solver.h"
#include "util.h"
#define P(i, j) p[(j) * (imax + 2) + (i)]
#define F(i, j) f[(j) * (imax + 2) + (i)]
#define G(i, j) g[(j) * (imax + 2) + (i)]
#define U(i, j) u[(j) * (imax + 2) + (i)]
#define V(i, j) v[(j) * (imax + 2) + (i)]
#define RHS(i, j) rhs[(j) * (imax + 2) + (i)]
static int sizeOfRank(int rank, int size, int N)
{
return N / size + ((N % size > rank) ? 1 : 0);
}
static void print(Solver* solver, double* grid)
{
int imax = solver->imax;
for (int i = 0; i < solver->size; i++) {
if (i == solver->rank) {
printf("### RANK %d "
"#######################################################\n",
solver->rank);
for (int j = 0; j < solver->jmaxLocal + 2; j++) {
printf("%02d: ", j);
for (int i = 0; i < solver->imax + 2; i++) {
printf("%12.8f ", grid[j * (imax + 2) + i]);
}
printf("\n");
}
fflush(stdout);
}
MPI_Barrier(MPI_COMM_WORLD);
}
}
static void exchange(Solver* solver, double* grid)
{
MPI_Request requests[4] = { MPI_REQUEST_NULL,
MPI_REQUEST_NULL,
MPI_REQUEST_NULL,
MPI_REQUEST_NULL };
/* exchange ghost cells with top neighbor */
if (solver->rank + 1 < solver->size) {
int top = solver->rank + 1;
double* src = grid + (solver->jmaxLocal) * (solver->imax + 2) + 1;
double* dst = grid + (solver->jmaxLocal + 1) * (solver->imax + 2) + 1;
MPI_Isend(src, solver->imax, MPI_DOUBLE, top, 1, MPI_COMM_WORLD, &requests[0]);
MPI_Irecv(dst, solver->imax, MPI_DOUBLE, top, 2, MPI_COMM_WORLD, &requests[1]);
}
/* exchange ghost cells with bottom neighbor */
if (solver->rank > 0) {
int bottom = solver->rank - 1;
double* src = grid + (solver->imax + 2) + 1;
double* dst = grid + 1;
MPI_Isend(src, solver->imax, MPI_DOUBLE, bottom, 2, MPI_COMM_WORLD, &requests[2]);
MPI_Irecv(dst, solver->imax, MPI_DOUBLE, bottom, 1, MPI_COMM_WORLD, &requests[3]);
}
MPI_Waitall(4, requests, MPI_STATUSES_IGNORE);
}
static void shift(Solver* solver)
{
MPI_Request requests[2] = { MPI_REQUEST_NULL, MPI_REQUEST_NULL };
double* g = solver->g;
/* shift G */
/* receive ghost cells from bottom neighbor */
if (solver->rank > 0) {
int bottom = solver->rank - 1;
MPI_Irecv(g + 1,
solver->imax,
MPI_DOUBLE,
bottom,
0,
MPI_COMM_WORLD,
&requests[0]);
}
if (solver->rank + 1 < solver->size) {
int top = solver->rank + 1;
double* buf = g + (solver->jmaxLocal) * (solver->imax + 2) + 1;
/* send ghost cells to top neighbor */
MPI_Isend(buf, solver->imax, MPI_DOUBLE, top, 0, MPI_COMM_WORLD, &requests[1]);
}
MPI_Waitall(2, requests, MPI_STATUSES_IGNORE);
}
void collectResult(Solver* solver)
{
double* Pall = NULL;
double* Uall = NULL;
double* Vall = NULL;
int *rcvCounts, *displs;
if (solver->rank == 0) {
Pall = allocate(64, (solver->imax + 2) * (solver->jmax + 2) * sizeof(double));
Uall = allocate(64, (solver->imax + 2) * (solver->jmax + 2) * sizeof(double));
Vall = allocate(64, (solver->imax + 2) * (solver->jmax + 2) * sizeof(double));
rcvCounts = (int*)malloc(solver->size * sizeof(int));
displs = (int*)malloc(solver->size * sizeof(int));
rcvCounts[0] = solver->jmaxLocal * (solver->imax + 2);
displs[0] = 0;
int cursor = rcvCounts[0];
for (int i = 1; i < solver->size; i++) {
rcvCounts[i] = sizeOfRank(i, solver->size, solver->jmax) * (solver->imax + 2);
displs[i] = cursor;
cursor += rcvCounts[i];
}
}
int cnt = solver->jmaxLocal * (solver->imax + 2);
double* sendbuffer = solver->p + (solver->imax + 2);
MPI_Gatherv(sendbuffer,
cnt,
MPI_DOUBLE,
Pall,
rcvCounts,
displs,
MPI_DOUBLE,
0,
MPI_COMM_WORLD);
sendbuffer = solver->u + (solver->imax + 2);
MPI_Gatherv(sendbuffer,
cnt,
MPI_DOUBLE,
Uall,
rcvCounts,
displs,
MPI_DOUBLE,
0,
MPI_COMM_WORLD);
sendbuffer = solver->v + (solver->imax + 2);
MPI_Gatherv(sendbuffer,
cnt,
MPI_DOUBLE,
Vall,
rcvCounts,
displs,
MPI_DOUBLE,
0,
MPI_COMM_WORLD);
if (solver->rank == 0) {
writeResult(solver, Pall, Uall, Vall);
}
}
static void printConfig(Solver* solver)
{
if (solver->rank == 0) {
printf("Parameters for #%s#\n", solver->problem);
printf("Boundary conditions Left:%d Right:%d Bottom:%d Top:%d\n",
solver->bcLeft,
solver->bcRight,
solver->bcBottom,
solver->bcTop);
printf("\tReynolds number: %.2f\n", solver->re);
printf("\tGx Gy: %.2f %.2f\n", solver->gx, solver->gy);
printf("Geometry data:\n");
printf("\tDomain box size (x, y): %.2f, %.2f\n",
solver->xlength,
solver->ylength);
printf("\tCells (x, y): %d, %d\n", solver->imax, solver->jmax);
printf("Timestep parameters:\n");
printf("\tDefault stepsize: %.2f, Final time %.2f\n", solver->dt, solver->te);
printf("\tdt bound: %.6f\n", solver->dtBound);
printf("\tTau factor: %.2f\n", solver->tau);
printf("Iterative solver parameters:\n");
printf("\tMax iterations: %d\n", solver->itermax);
printf("\tepsilon (stopping tolerance) : %f\n", solver->eps);
printf("\tgamma factor: %f\n", solver->gamma);
printf("\tomega (SOR relaxation): %f\n", solver->omega);
printf("Communication parameters:\n");
}
for (int i = 0; i < solver->size; i++) {
if (i == solver->rank) {
printf("\tRank %d of %d\n", solver->rank, solver->size);
printf("\tLocal domain size: %dx%d\n", solver->imax, solver->jmaxLocal);
fflush(stdout);
}
}
}
void initSolver(Solver* solver, Parameter* params)
{
MPI_Comm_rank(MPI_COMM_WORLD, &(solver->rank));
MPI_Comm_size(MPI_COMM_WORLD, &(solver->size));
solver->problem = params->name;
solver->bcLeft = params->bcLeft;
solver->bcRight = params->bcRight;
solver->bcBottom = params->bcBottom;
solver->bcTop = params->bcTop;
solver->imax = params->imax;
solver->jmax = params->jmax;
solver->jmaxLocal = sizeOfRank(solver->rank, solver->size, solver->jmax);
solver->xlength = params->xlength;
solver->ylength = params->ylength;
solver->dx = params->xlength / params->imax;
solver->dy = params->ylength / params->jmax;
solver->eps = params->eps;
solver->omega = params->omg;
solver->itermax = params->itermax;
solver->re = params->re;
solver->gx = params->gx;
solver->gy = params->gy;
solver->dt = params->dt;
solver->te = params->te;
solver->tau = params->tau;
solver->gamma = params->gamma;
solver->rho = params->rho;
int imax = solver->imax;
int jmaxLocal = solver->jmaxLocal;
size_t bytesize = (imax + 2) * (jmaxLocal + 2) * sizeof(double);
solver->u = allocate(64, bytesize);
solver->v = allocate(64, bytesize);
solver->p = allocate(64, bytesize);
solver->rhs = allocate(64, bytesize);
solver->f = allocate(64, bytesize);
solver->g = allocate(64, bytesize);
for (int i = 0; i < (imax + 2) * (jmaxLocal + 2); i++) {
solver->u[i] = params->u_init;
solver->v[i] = params->v_init;
solver->p[i] = params->p_init;
solver->rhs[i] = 0.0;
solver->f[i] = 0.0;
solver->g[i] = 0.0;
}
double dx = solver->dx;
double dy = solver->dy;
double inv_sqr_sum = 1.0 / (dx * dx) + 1.0 / (dy * dy);
solver->dtBound = 0.5 * solver->re * 1.0 / inv_sqr_sum;
#ifdef VERBOSE
printConfig(solver);
#endif
}
void computeRHS(Solver* solver)
{
int imax = solver->imax;
int jmaxLocal = solver->jmaxLocal;
double idx = 1.0 / solver->dx;
double idy = 1.0 / solver->dy;
double idt = 1.0 / solver->dt;
double* rhs = solver->rhs;
double* f = solver->f;
double* g = solver->g;
shift(solver);
for (int j = 1; j < jmaxLocal + 1; j++) {
for (int i = 1; i < imax + 1; i++) {
RHS(i, j) = ((F(i, j) - F(i - 1, j)) * idx + (G(i, j) - G(i, j - 1)) * idy) *
idt;
}
}
}
void solve(Solver* solver)
{
int imax = solver->imax;
int jmax = solver->jmax;
int jmaxLocal = solver->jmaxLocal;
double eps = solver->eps;
int itermax = solver->itermax;
double dx2 = solver->dx * solver->dx;
double dy2 = solver->dy * solver->dy;
double idx2 = 1.0 / dx2;
double idy2 = 1.0 / dy2;
double factor = solver->omega * 0.5 * (dx2 * dy2) / (dx2 + dy2);
double* p = solver->p;
double* rhs = solver->rhs;
double epssq = eps * eps;
int it = 0;
double res = 1.0;
while ((res >= epssq) && (it < itermax)) {
res = 0.0;
exchange(solver, p);
for (int j = 1; j < jmaxLocal + 1; j++) {
for (int i = 1; i < imax + 1; i++) {
double r = RHS(i, j) -
((P(i + 1, j) - 2.0 * P(i, j) + P(i - 1, j)) * idx2 +
(P(i, j + 1) - 2.0 * P(i, j) + P(i, j - 1)) * idy2);
P(i, j) -= (factor * r);
res += (r * r);
}
}
if (solver->rank == 0) {
for (int i = 1; i < imax + 1; i++) {
P(i, 0) = P(i, 1);
}
}
if (solver->rank == (solver->size - 1)) {
for (int i = 1; i < imax + 1; i++) {
P(i, jmaxLocal + 1) = P(i, jmaxLocal);
}
}
for (int j = 1; j < jmaxLocal + 1; j++) {
P(0, j) = P(1, j);
P(imax + 1, j) = P(imax, j);
}
MPI_Allreduce(MPI_IN_PLACE, &res, 1, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
res = res / (double)(imax * jmax);
#ifdef DEBUG
if (solver->rank == 0) {
printf("%d Residuum: %e\n", it, res);
}
#endif
it++;
}
#ifdef VERBOSE
if (solver->rank == 0) {
printf("Solver took %d iterations to reach %f\n", it, sqrt(res));
}
#endif
}
void solveRB(Solver* solver)
{
int imax = solver->imax;
int jmax = solver->jmax;
int jmaxLocal = solver->jmaxLocal;
double eps = solver->eps;
int itermax = solver->itermax;
double dx2 = solver->dx * solver->dx;
double dy2 = solver->dy * solver->dy;
double idx2 = 1.0 / dx2;
double idy2 = 1.0 / dy2;
double factor = solver->omega * 0.5 * (dx2 * dy2) / (dx2 + dy2);
double* p = solver->p;
double* rhs = solver->rhs;
double epssq = eps * eps;
int it = 0;
double res = 1.0;
int pass, jsw, isw;
while ((res >= epssq) && (it < itermax)) {
jsw = 1;
for (pass = 0; pass < 2; pass++) {
isw = jsw;
exchange(solver, p);
for (int j = 1; j < jmaxLocal + 1; j++) {
for (int i = isw; i < imax + 1; i += 2) {
double r = RHS(i, j) -
((P(i + 1, j) - 2.0 * P(i, j) + P(i - 1, j)) * idx2 +
(P(i, j + 1) - 2.0 * P(i, j) + P(i, j - 1)) * idy2);
P(i, j) -= (factor * r);
res += (r * r);
}
isw = 3 - isw;
}
jsw = 3 - jsw;
}
if (solver->rank == 0) {
for (int i = 1; i < imax + 1; i++) {
P(i, 0) = P(i, 1);
}
}
if (solver->rank == (solver->size - 1)) {
for (int i = 1; i < imax + 1; i++) {
P(i, jmaxLocal + 1) = P(i, jmaxLocal);
}
}
for (int j = 1; j < jmaxLocal + 1; j++) {
P(0, j) = P(1, j);
P(imax + 1, j) = P(imax, j);
}
MPI_Allreduce(MPI_IN_PLACE, &res, 1, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
res = res / (double)(imax * jmax);
#ifdef DEBUG
if (solver->rank == 0) {
printf("%d Residuum: %e\n", it, res);
}
#endif
it++;
}
#ifdef VERBOSE
if (solver->rank == 0) {
printf("Solver took %d iterations to reach %f\n", it, sqrt(res));
}
#endif
}
void solveRBA(Solver* solver)
{
int imax = solver->imax;
int jmax = solver->jmax;
int jmaxLocal = solver->jmaxLocal;
double eps = solver->eps;
int itermax = solver->itermax;
double dx2 = solver->dx * solver->dx;
double dy2 = solver->dy * solver->dy;
double idx2 = 1.0 / dx2;
double idy2 = 1.0 / dy2;
double factor = 0.5 * (dx2 * dy2) / (dx2 + dy2);
double* p = solver->p;
double* rhs = solver->rhs;
double rho = solver->rho;
double epssq = eps * eps;
int it = 0;
double res = 1.0;
double omega = 1.0;
int pass, jsw, isw;
while ((res >= epssq) && (it < itermax)) {
res = 0.0;
jsw = 1;
for (pass = 0; pass < 2; pass++) {
isw = jsw;
exchange(solver, p);
for (int j = 1; j < jmaxLocal + 1; j++) {
for (int i = isw; i < imax + 1; i += 2) {
double r = RHS(i, j) -
((P(i + 1, j) - 2.0 * P(i, j) + P(i - 1, j)) * idx2 +
(P(i, j + 1) - 2.0 * P(i, j) + P(i, j - 1)) * idy2);
P(i, j) -= (omega * factor * r);
res += (r * r);
}
isw = 3 - isw;
}
jsw = 3 - jsw;
omega = (it == 0 && pass == 0 ? 1.0 / (1.0 - 0.5 * rho * rho)
: 1.0 / (1.0 - 0.25 * rho * rho * omega));
}
if (solver->rank == 0) {
for (int i = 1; i < imax + 1; i++) {
P(i, 0) = P(i, 1);
}
}
if (solver->rank == (solver->size - 1)) {
for (int i = 1; i < imax + 1; i++) {
P(i, jmaxLocal + 1) = P(i, jmaxLocal);
}
}
for (int j = 1; j < jmaxLocal + 1; j++) {
P(0, j) = P(1, j);
P(imax + 1, j) = P(imax, j);
}
MPI_Allreduce(MPI_IN_PLACE, &res, 1, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
res = res / (double)(imax * jmax);
#ifdef DEBUG
if (solver->rank == 0) {
printf("%d Residuum: %e\n", it, res);
}
#endif
it++;
}
#ifdef VERBOSE
if (solver->rank == 0) {
printf("Solver took %d iterations to reach %f\n", it, sqrt(res));
}
#endif
}
static double maxElement(Solver* solver, double* m)
{
int size = (solver->imax + 2) * (solver->jmaxLocal + 2);
double maxval = DBL_MIN;
for (int i = 0; i < size; i++) {
maxval = MAX(maxval, fabs(m[i]));
}
MPI_Allreduce(MPI_IN_PLACE, &maxval, 1, MPI_DOUBLE, MPI_MAX, MPI_COMM_WORLD);
return maxval;
}
void normalizePressure(Solver* solver)
{
int size = (solver->imax + 2) * (solver->jmaxLocal + 2);
double* p = solver->p;
double avgP = 0.0;
for (int i = 0; i < size; i++) {
avgP += p[i];
}
MPI_Allreduce(MPI_IN_PLACE, &avgP, 1, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);
avgP /= (solver->imax + 2) * (solver->jmax + 2);
for (int i = 0; i < size; i++) {
p[i] = p[i] - avgP;
}
}
void computeTimestep(Solver* solver)
{
double dt = solver->dtBound;
double dx = solver->dx;
double dy = solver->dy;
double umax = maxElement(solver, solver->u);
double vmax = maxElement(solver, solver->v);
if (umax > 0) {
dt = (dt > dx / umax) ? dx / umax : dt;
}
if (vmax > 0) {
dt = (dt > dy / vmax) ? dy / vmax : dt;
}
solver->dt = dt * solver->tau;
}
void setBoundaryConditions(Solver* solver)
{
int imax = solver->imax;
int jmaxLocal = solver->jmaxLocal;
double* u = solver->u;
double* v = solver->v;
// Left boundary
switch (solver->bcLeft) {
case NOSLIP:
for (int j = 1; j < jmaxLocal + 1; j++) {
U(0, j) = 0.0;
V(0, j) = -V(1, j);
}
break;
case SLIP:
for (int j = 1; j < jmaxLocal + 1; j++) {
U(0, j) = 0.0;
V(0, j) = V(1, j);
}
break;
case OUTFLOW:
for (int j = 1; j < jmaxLocal + 1; j++) {
U(0, j) = U(1, j);
V(0, j) = V(1, j);
}
break;
case PERIODIC:
break;
}
// Right boundary
switch (solver->bcRight) {
case NOSLIP:
for (int j = 1; j < jmaxLocal + 1; j++) {
U(imax, j) = 0.0;
V(imax + 1, j) = -V(imax, j);
}
break;
case SLIP:
for (int j = 1; j < jmaxLocal + 1; j++) {
U(imax, j) = 0.0;
V(imax + 1, j) = V(imax, j);
}
break;
case OUTFLOW:
for (int j = 1; j < jmaxLocal + 1; j++) {
U(imax, j) = U(imax - 1, j);
V(imax + 1, j) = V(imax, j);
}
break;
case PERIODIC:
break;
}
// Bottom boundary
if (solver->rank == 0) {
switch (solver->bcBottom) {
case NOSLIP:
for (int i = 1; i < imax + 1; i++) {
V(i, 0) = 0.0;
U(i, 0) = -U(i, 1);
}
break;
case SLIP:
for (int i = 1; i < imax + 1; i++) {
V(i, 0) = 0.0;
U(i, 0) = U(i, 1);
}
break;
case OUTFLOW:
for (int i = 1; i < imax + 1; i++) {
U(i, 0) = U(i, 1);
V(i, 0) = V(i, 1);
}
break;
case PERIODIC:
break;
}
}
// Top boundary
if (solver->rank == (solver->size - 1)) {
switch (solver->bcTop) {
case NOSLIP:
for (int i = 1; i < imax + 1; i++) {
V(i, jmaxLocal) = 0.0;
U(i, jmaxLocal + 1) = -U(i, jmaxLocal);
}
break;
case SLIP:
for (int i = 1; i < imax + 1; i++) {
V(i, jmaxLocal) = 0.0;
U(i, jmaxLocal + 1) = U(i, jmaxLocal);
}
break;
case OUTFLOW:
for (int i = 1; i < imax + 1; i++) {
U(i, jmaxLocal + 1) = U(i, jmaxLocal);
V(i, jmaxLocal) = V(i, jmaxLocal - 1);
}
break;
case PERIODIC:
break;
}
}
}
void setSpecialBoundaryCondition(Solver* solver)
{
int imax = solver->imax;
int jmaxLocal = solver->jmaxLocal;
double* u = solver->u;
if (strcmp(solver->problem, "dcavity") == 0) {
if (solver->rank == (solver->size - 1)) {
for (int i = 1; i < imax; i++) {
U(i, jmaxLocal + 1) = 2.0 - U(i, jmaxLocal);
}
}
} else if (strcmp(solver->problem, "canal") == 0) {
double ylength = solver->ylength;
double dy = solver->dy;
int rest = solver->jmax % solver->size;
int yc = solver->rank * (solver->jmax / solver->size) + MIN(rest, solver->rank);
double ys = dy * (yc + 0.5);
double y;
/* printf("RANK %d yc: %d ys: %f\n", solver->rank, yc, ys); */
for (int j = 1; j < jmaxLocal + 1; j++) {
y = ys + dy * (j - 0.5);
U(0, j) = y * (ylength - y) * 4.0 / (ylength * ylength);
}
}
/* print(solver, solver->u); */
}
void computeFG(Solver* solver)
{
double* u = solver->u;
double* v = solver->v;
double* f = solver->f;
double* g = solver->g;
int imax = solver->imax;
int jmaxLocal = solver->jmaxLocal;
double gx = solver->gx;
double gy = solver->gy;
double gamma = solver->gamma;
double dt = solver->dt;
double inverseRe = 1.0 / solver->re;
double inverseDx = 1.0 / solver->dx;
double inverseDy = 1.0 / solver->dy;
double du2dx, dv2dy, duvdx, duvdy;
double du2dx2, du2dy2, dv2dx2, dv2dy2;
exchange(solver, u);
exchange(solver, v);
for (int j = 1; j < jmaxLocal + 1; j++) {
for (int i = 1; i < imax + 1; i++) {
du2dx = inverseDx * 0.25 *
((U(i, j) + U(i + 1, j)) * (U(i, j) + U(i + 1, j)) -
(U(i, j) + U(i - 1, j)) * (U(i, j) + U(i - 1, j))) +
gamma * inverseDx * 0.25 *
(fabs(U(i, j) + U(i + 1, j)) * (U(i, j) - U(i + 1, j)) +
fabs(U(i, j) + U(i - 1, j)) * (U(i, j) - U(i - 1, j)));
duvdy = inverseDy * 0.25 *
((V(i, j) + V(i + 1, j)) * (U(i, j) + U(i, j + 1)) -
(V(i, j - 1) + V(i + 1, j - 1)) * (U(i, j) + U(i, j - 1))) +
gamma * inverseDy * 0.25 *
(fabs(V(i, j) + V(i + 1, j)) * (U(i, j) - U(i, j + 1)) +
fabs(V(i, j - 1) + V(i + 1, j - 1)) *
(U(i, j) - U(i, j - 1)));
du2dx2 = inverseDx * inverseDx * (U(i + 1, j) - 2.0 * U(i, j) + U(i - 1, j));
du2dy2 = inverseDy * inverseDy * (U(i, j + 1) - 2.0 * U(i, j) + U(i, j - 1));
F(i, j) = U(i, j) + dt * (inverseRe * (du2dx2 + du2dy2) - du2dx - duvdy + gx);
duvdx = inverseDx * 0.25 *
((U(i, j) + U(i, j + 1)) * (V(i, j) + V(i + 1, j)) -
(U(i - 1, j) + U(i - 1, j + 1)) * (V(i, j) + V(i - 1, j))) +
gamma * inverseDx * 0.25 *
(fabs(U(i, j) + U(i, j + 1)) * (V(i, j) - V(i + 1, j)) +
fabs(U(i - 1, j) + U(i - 1, j + 1)) *
(V(i, j) - V(i - 1, j)));
dv2dy = inverseDy * 0.25 *
((V(i, j) + V(i, j + 1)) * (V(i, j) + V(i, j + 1)) -
(V(i, j) + V(i, j - 1)) * (V(i, j) + V(i, j - 1))) +
gamma * inverseDy * 0.25 *
(fabs(V(i, j) + V(i, j + 1)) * (V(i, j) - V(i, j + 1)) +
fabs(V(i, j) + V(i, j - 1)) * (V(i, j) - V(i, j - 1)));
dv2dx2 = inverseDx * inverseDx * (V(i + 1, j) - 2.0 * V(i, j) + V(i - 1, j));
dv2dy2 = inverseDy * inverseDy * (V(i, j + 1) - 2.0 * V(i, j) + V(i, j - 1));
G(i, j) = V(i, j) + dt * (inverseRe * (dv2dx2 + dv2dy2) - duvdx - dv2dy + gy);
}
}
/* ----------------------------- boundary of F ---------------------------
*/
for (int j = 1; j < jmaxLocal + 1; j++) {
F(0, j) = U(0, j);
F(imax, j) = U(imax, j);
}
/* ----------------------------- boundary of G ---------------------------
*/
if (solver->rank == 0) {
for (int i = 1; i < imax + 1; i++) {
G(i, 0) = V(i, 0);
}
}
if (solver->rank == (solver->size - 1)) {
for (int i = 1; i < imax + 1; i++) {
G(i, jmaxLocal) = V(i, jmaxLocal);
}
}
}
void adaptUV(Solver* solver)
{
int imax = solver->imax;
int jmaxLocal = solver->jmaxLocal;
double* p = solver->p;
double* u = solver->u;
double* v = solver->v;
double* f = solver->f;
double* g = solver->g;
double factorX = solver->dt / solver->dx;
double factorY = solver->dt / solver->dy;
for (int j = 1; j < jmaxLocal + 1; j++) {
for (int i = 1; i < imax + 1; i++) {
U(i, j) = F(i, j) - (P(i + 1, j) - P(i, j)) * factorX;
V(i, j) = G(i, j) - (P(i, j + 1) - P(i, j)) * factorY;
}
}
}
void writeResult(Solver* solver, double* p, double* u, double* v)
{
int imax = solver->imax;
int jmax = solver->jmax;
double dx = solver->dx;
double dy = solver->dy;
double x = 0.0, y = 0.0;
FILE* fp;
fp = fopen("pressure.dat", "w");
if (fp == NULL) {
printf("Error!\n");
exit(EXIT_FAILURE);
}
for (int j = 1; j < jmax + 1; j++) {
y = (double)(j - 0.5) * dy;
for (int i = 1; i < imax + 1; i++) {
x = (double)(i - 0.5) * dx;
fprintf(fp, "%.2f %.2f %f\n", x, y, P(i, j));
}
fprintf(fp, "\n");
}
fclose(fp);
fp = fopen("velocity.dat", "w");
if (fp == NULL) {
printf("Error!\n");
exit(EXIT_FAILURE);
}
for (int j = 1; j < jmax + 1; j++) {
y = dy * (j - 0.5);
for (int i = 1; i < imax + 1; i++) {
x = dx * (i - 0.5);
double vel_u = (U(i, j) + U(i - 1, j)) / 2.0;
double vel_v = (V(i, j) + V(i, j - 1)) / 2.0;
double len = sqrt((vel_u * vel_u) + (vel_v * vel_v));
fprintf(fp, "%.2f %.2f %f %f %f\n", x, y, vel_u, vel_v, len);
}
}
fclose(fp);
}
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