ft: hybrid implementation for mg solve v0

EnhancedSolver/2D-mpi/src/discretization.c

@@ -114,7 +114,9 @@ void initDiscretiztion(Discretization* d, Parameter* params)
     d->f      = allocate(64, size * sizeof(double));
     d->g      = allocate(64, size * sizeof(double));
     d->grid.s = allocate(64, size * sizeof(double));
-
+    #ifdef _OPENMP
+    #pragma omp parallel for  
+    #endif
     for (int i = 0; i < size; i++) {
         d->u[i]      = params->u_init;
         d->v[i]      = params->v_init;

EnhancedSolver/2D-mpi/src/solver-mg.c

@@ -6,6 +6,7 @@
  */
 #include <stdio.h>
 #include <stdlib.h>
+#include <omp.h>
 
 #include "allocate.h"
 #include "solver.h"
@@ -53,7 +54,9 @@ static void restrictMG(Solver* s, int level, Comm* comm)
 #ifdef _MPI
     commExchange(comm, old);
 #endif
-
+    #ifdef _OPENMP
+    #pragma omp parallel for   
+    #endif
     for (int j = 1; j < (jmaxLocal / 2) + 1; j++) {
         for (int i = 1; i < (imaxLocal / 2) + 1; i++) {
             R(i, j) = (OLD(2 * i - 1, 2 * j - 1) + OLD(2 * i, 2 * j - 1) * 2 +
@@ -73,7 +76,9 @@ static void prolongate(Solver* s, int level, Comm* comm)
 
     double* old = s->r[level + 1];
     double* e   = s->r[level];
-
+    #ifdef _OPENMP
+    #pragma omp parallel for   
+    #endif
     for (int j = 2; j < jmaxLocal + 1; j += 2) {
         for (int i = 2; i < imaxLocal + 1; i += 2) {
             E(i, j) = OLD(i / 2, j / 2);
@@ -87,6 +92,9 @@ static void correct(Solver* s, double* p, int level, Comm* comm)
     int imaxLocal = comm->imaxLocal;
     int jmaxLocal = comm->jmaxLocal;
 
+    #ifdef _OPENMP
+    #pragma omp parallel for   
+    #endif
     for (int j = 1; j < jmaxLocal + 1; ++j) {
         for (int i = 1; i < imaxLocal + 1; ++i) {
             P(i, j) += E(i, j);
@@ -97,25 +105,38 @@ static void correct(Solver* s, double* p, int level, Comm* comm)
 static void setBoundaryCondition(Solver* s, double* p, int imaxLocal, int jmaxLocal)
 {
 #ifdef _MPI
+    
     if (commIsBoundary(s->comm, B)) { // set bottom bc
+        #ifdef _OPENMP
+        #pragma omp parallel for   
+        #endif    
         for (int i = 1; i < imaxLocal + 1; i++) {
             P(i, 0) = P(i, 1);
         }
     }
 
     if (commIsBoundary(s->comm, T)) { // set top bc
+        #ifdef _OPENMP
+        #pragma omp parallel for   
+        #endif   
         for (int i = 1; i < imaxLocal + 1; i++) {
             P(i, jmaxLocal + 1) = P(i, jmaxLocal);
         }
     }
 
     if (commIsBoundary(s->comm, L)) { // set left bc
+        #ifdef _OPENMP
+        #pragma omp parallel for   
+        #endif    
         for (int j = 1; j < jmaxLocal + 1; j++) {
             P(0, j) = P(1, j);
         }
     }
 
     if (commIsBoundary(s->comm, R)) { // set right bc
+        #ifdef _OPENMP
+        #pragma omp parallel for   
+        #endif    
         for (int j = 1; j < jmaxLocal + 1; j++) {
             P(imaxLocal + 1, j) = P(imaxLocal, j);
         }
@@ -160,10 +181,14 @@ static void smooth(Solver* s, double* p, double* rhs, int level, Comm* comm)
 #ifdef _MPI
         commExchange(comm, p);
 #endif
-
+        #ifdef _OPENMP
+        #pragma message("Enabling OPENMP for loop")
+        #pragma omp parallel private(isw)
+        {
+            isw = jsw;
+            #pragma omp for 
             for (int j = 1; j < jmaxLocal + 1; j++) {
                 for (int i = isw; i < imaxLocal + 1; i += 2) {        
-
                     P(i, j) -= factor *
                     (RHS(i, j) -
                     ((P(i + 1, j) - 2.0 * P(i, j) + P(i - 1, j)) * idx2 +
@@ -171,6 +196,18 @@ static void smooth(Solver* s, double* p, double* rhs, int level, Comm* comm)
                 }
                 isw = 3 - isw;
             }
+        }
+        #else
+        for (int j = 1; j < jmaxLocal + 1; j++) {
+            for (int i = isw; i < imaxLocal + 1; i += 2) {        
+                P(i, j) -= factor *
+                (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));
+            }
+            isw = 3 - isw;
+        }
+        #endif
         jsw = 3 - jsw;
     }
 }
@@ -199,7 +236,11 @@ static double calculateResidual(Solver* s, double* p, double* rhs, int level, Co
 #ifdef _MPI
         commExchange(comm, p);
 #endif
-
+        #ifdef _OPENMP
+        #pragma omp parallel private(isw)
+        {
+            isw = jsw;
+            #pragma omp for  
             for (int j = 1; j < jmaxLocal + 1; j++) {
                 for (int i = isw; i < imaxLocal + 1; i += 2) {
                     
@@ -211,6 +252,20 @@ static double calculateResidual(Solver* s, double* p, double* rhs, int level, Co
                 }
                 isw = 3 - isw;
             }
+        }
+        #else
+        for (int j = 1; j < jmaxLocal + 1; j++) {
+            for (int i = isw; i < imaxLocal + 1; i += 2) {
+
+                R(i, j) = 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);
+
+                res += (R(i, j) * R(i, j));
+            }
+            isw = 3 - isw;
+        }
+        #endif
         jsw = 3 - jsw;
     }
 
@@ -297,6 +352,17 @@ void initSolver(Solver* s, Discretization* d, Parameter* p)
     int jmax   = s->grid->jmax;
     int levels = s->levels;
     printf("Using Multigrid solver with %d levels\n", levels);
+    #ifdef _MPI
+        #ifdef _OPENMP
+    if (commIsMaster(s->comm)) {
+        #pragma omp parallel
+        {
+            #pragma omp single
+            printf("Detected %d threads per rank (%d)\n", omp_get_num_threads(), s->comm->size);
+        }
+    }
+        #endif
+    #endif
 
     s->r = malloc(levels * sizeof(double*));
     s->e = malloc(levels * sizeof(double*));