diff --git a/PoissonSolver/2D-mpi-sq/src/main.c b/PoissonSolver/2D-mpi-sq/src/main.c
index 7c3f8b8..89e92d1 100644
--- a/PoissonSolver/2D-mpi-sq/src/main.c
+++ b/PoissonSolver/2D-mpi-sq/src/main.c
@@ -32,9 +32,9 @@ int main(int argc, char** argv)
 
     readParameter(&params, argv[1]);
     initSolver(&solver, &params, 2);
-    // startTime = getTimeStamp();
-    // solveRB(&solver);
-    // endTime = getTimeStamp();
+    startTime = getTimeStamp();
+    solveRB(&solver);
+    endTime = getTimeStamp();
     writeResult(&solver, "p.dat");
     // printf(" %.2fs\n", endTime - startTime);
     // writeResult(&solver, "p.dat");
diff --git a/PoissonSolver/2D-mpi-sq/src/solver.c b/PoissonSolver/2D-mpi-sq/src/solver.c
index 0f979e1..d2091be 100644
--- a/PoissonSolver/2D-mpi-sq/src/solver.c
+++ b/PoissonSolver/2D-mpi-sq/src/solver.c
@@ -60,6 +60,15 @@ void initSolver(Solver* solver, Parameter* params, int problem)
         0,
         &solver->cart_comm);
     MPI_Cart_coords(solver->cart_comm, rank, 2, solver->coords);
+    solver->boundary = NB;
+    int x_low, x_high, y_low, y_high;
+    MPI_Cart_shift(solver->cart_comm, 0, 1, &x_low, &x_high);
+    MPI_Cart_shift(solver->cart_comm, 1, 1, &y_low, &y_high);
+    if (x_low == MPI_PROC_NULL) solver->boundary += BOTTOM;
+    if (y_low == MPI_PROC_NULL) solver->boundary += LEFT;
+    if (x_high == MPI_PROC_NULL) solver->boundary += TOP;
+    if (y_high == MPI_PROC_NULL) solver->boundary += RIGHT;
+
     solver->limax = distribute_dim(solver->coords[0], solver->dims[0], solver->imax);
     solver->ljmax = distribute_dim(solver->coords[1], solver->dims[1], solver->jmax);
 
@@ -107,11 +116,11 @@ void initSolver(Solver* solver, Parameter* params, int problem)
         i_start,
         j_start);
     fflush(stdout);
-    for (int i = 0; i < solver->limax + 2; i++) {
-        for (int j = 0; j < solver->ljmax + 2; j++) {
-            P(i, j) = rank;
-        }
-    }
+    // for (int i = 0; i < solver->limax + 2; i++) {
+    //     for (int j = 0; j < solver->ljmax + 2; j++) {
+    //         P(i, j) = (double)solver->boundary;
+    //     }
+    // }
     for (int i = 0; i < solver->limax + 2; i++) {
         for (int j = 0; j < solver->ljmax + 2; j++) {
             P(i, j) = sin(2.0 * PI * (i_start + i) * dx * 2.0) +
@@ -181,16 +190,19 @@ void solveRB(Solver* solver)
             }
             jsw = 3 - jsw;
         }
-        //
-        // for (int i = 1; i < imax + 1; i++) {
-        //     P(i, 0)        = P(i, 1);
-        //     P(i, jmax + 1) = P(i, jmax);
-        // }
-        //
-        // for (int j = 1; j < jmax + 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);
+        if (solver->boundary & BOTTOM)
+            for (int j = 1; j < solver->ljmax + 1; j++)
+                P(0, j) = P(1, j);
+        if (solver->boundary & TOP)
+            for (int j = 1; j < solver->ljmax + 1; j++)
+                P(solver->limax + 1, j) = P(solver->limax, j);
+        if (solver->boundary & LEFT)
+            for (int i = 1; i < solver->limax + 1; i++)
+                P(i, 0) = P(i, 1);
+        if (solver->boundary & RIGHT)
+            for (int i = 1; i < solver->limax + 1; i++)
+                P(i, solver->ljmax + 1) = P(i, solver->ljmax);
 
         res = res / (double)(imax * jmax);
 #ifdef DEBUG
@@ -199,8 +211,7 @@ void solveRB(Solver* solver)
         it++;
     }
 
-    // printf("Solver took %d iterations to reach %f\n", it, sqrt(res));
-    printf("%d, %f\n", it, solver->omega);
+    if(solver->rank==0) printf("Solver took %d iterations to reach %f\n", it, sqrt(res));
 }
 
 void writeResult(Solver* solver, char* filename)
diff --git a/PoissonSolver/2D-mpi-sq/src/solver.h b/PoissonSolver/2D-mpi-sq/src/solver.h
index 42d3eac..0b87fa6 100644
--- a/PoissonSolver/2D-mpi-sq/src/solver.h
+++ b/PoissonSolver/2D-mpi-sq/src/solver.h
@@ -6,11 +6,23 @@
 #define __SOLVER_H_
 #include "parameter.h"
 #include <mpi.h>
+typedef enum {
+    NB     = 0b0000,
+    LEFT   = 0b0001,
+    RIGHT  = 0b0010,
+    TOP    = 0b0100,
+    BOTTOM = 0b1000,
+    LFTO   = LEFT + TOP,
+    LFBO   = LEFT + BOTTOM,
+    RITO   = RIGHT + TOP,
+    ROBO   = RIGHT + BOTTOM
+} boundary_t;
 
 typedef struct {
+
     double dx, dy;
     int imax, jmax;
-    int limax,ljmax;
+    int limax, ljmax;
     double *p, *rhs;
     double eps, omega, rho;
     int itermax;
@@ -21,6 +33,8 @@ typedef struct {
     int coords[2];
     int dims[2];
     int rank, size;
+    boundary_t boundary;
+
 } Solver;
 
 extern void initSolver(Solver*, Parameter*, int problem);