ModSim ass4 taddeus: Fixed MPI implementation (finally...).

modsim/ass4_taddeus/vibstring/par.c

@@ -14,19 +14,18 @@ FILE *file;
  * receiving the outer borders calculated by the adjacent nodes
  */
 void interact(int state) {
-    int prev = (rank - 1 + tasks) % tasks, next = (rank + 1) % tasks;
     MPI_Status status;
 
     // Left border
     if( rank ) {
-        MPI_Sendrecv(y[state] + 1, 1, MPI_DOUBLE, prev, 0, y[state], 1,
-                MPI_DOUBLE, prev, MPI_ANY_TAG, MPI_COMM_WORLD, &status);
+        MPI_Sendrecv(y[state] + 1, 1, MPI_DOUBLE, rank - 1, 0, y[state], 1,
+                MPI_DOUBLE, rank - 1, MPI_ANY_TAG, MPI_COMM_WORLD, &status);
     }
 
     // Right border
     if( rank < tasks - 1 ) {
-        MPI_Sendrecv(y[state] + steps, 1, MPI_DOUBLE, next, 0,
-                y[state] + steps + 1, 1, MPI_DOUBLE, next, MPI_ANY_TAG,
+        MPI_Sendrecv(y[state] + steps, 1, MPI_DOUBLE, rank + 1, 0,
+                y[state] + steps + 1, 1, MPI_DOUBLE, rank + 1, MPI_ANY_TAG,
                 MPI_COMM_WORLD, &status);
     }
 }
@@ -38,17 +37,14 @@ void init_borders() {
     else if( rank == tasks - 1 )
         y[2][steps] = y[1][steps] = y[0][steps];
 
-    //interact(0);
+    interact(0);
 }
 
 /*
  * Fill the assigned string section with a sinus shape
  */
 void init_sinus(double l, double dx, double n) {
-    int i;
-    printf("start: %d\n", start);
-
-    for( i = 0; i < steps; i++ )
+    for( int i = 0; i < steps; i++ )
         y[0][i + 1] = sin(n * M_PI * (i + start) * dx / l);
 
     init_borders();
@@ -59,9 +55,8 @@ void init_sinus(double l, double dx, double n) {
  */
 void init_plucked(double l, double dx, double xp) {
     double x;
-    int i;
 
-    for( i = 0; i < steps; i++ ) {
+    for( int i = 0; i < steps; i++ ) {
         x = (i + start) * dx;
         y[0][i + 1] = x < xp ? x / xp : (l - x) / (l - xp);
     }
@@ -75,8 +70,8 @@ void init_plucked(double l, double dx, double xp) {
 #define PRINT_FORMAT "%e"
 
 void print(int index) {
-    for( int i = 0; i < steps; i++ ) {
-        if( i )
+    for( int i = 1; i <= steps; i++ ) {
+        if( i > 1 )
             fprintf(file, " ");
 
         fprintf(file, PRINT_FORMAT, y[index][i]);
@@ -91,16 +86,19 @@ void print(int index) {
  */
 void calculate_steps(int time, double dx, double tau) {
     double x;
-    int i, t, prev = 0, current = 1, next = 2;
+    int i, t, prev = 0, current = 1, next = 2,
+        s = rank ? 1 : 2, e = rank == tasks - 1 ? steps - 1 : steps;
 
     // Calculate the position over the entire string at time dt using the
     // position at t = 0 and the information that y(x, -dt) == y(x, dt)
-    for( i = 1; i <= steps; i++ ) {
+    for( i = s; i <= e; i++ ) {
         x = i * dx;
-        y[1][i] = y[0][i] + .5 * tau * tau * (y[0][i-1] - 2 * y[0][i]
-                  + y[0][i+1]);
+        y[current][i] = y[0][i] + .5 * tau * tau * (y[0][i - 1] - 2 * y[0][i]
+                  + y[0][i + 1]);
     }
 
+    interact(current);
+
     #ifdef VERBOSE
     // Print x values (which are the same for every y-series)
     for( i = 0; i < steps; i++ ) {
@@ -119,11 +117,13 @@ void calculate_steps(int time, double dx, double tau) {
 
     // Iterate over the length of the string for each time interval step
     for( t = 2; t < time; t++ ) {
-        for( i = 1; i <= steps; i++ ) {
+        for( i = s; i <= e; i++ ) {
             y[next][i] = 2 * y[current][i] - y[prev][i] + tau * tau
                 * (y[current][i-1] - 2 * y[current][i] + y[current][i+1]);
         }
 
+        interact(next);
+
         #ifdef VERBOSE
         print(next);
         #endif
@@ -131,8 +131,6 @@ void calculate_steps(int time, double dx, double tau) {
         prev = current;
         current = next;
         next = (next + 1) % 3;
-
-        interact(next);
     }
 }
 
@@ -187,7 +185,7 @@ int main(int argc, char **argv) {
     // allocate the left and right outer border values that are calculated by
     // other nodes
     if( rank == tasks - 1 )
-        steps += total_steps - steps * (tasks - 1);
+        steps += total_steps % steps;
 
     // Allocate a 3xN two-dimensional area for this part of the string that
     // functions as a cyclic buffer for three states of the string (previous,

modsim/ass4_taddeus/vibstring/par.sh

@@ -6,7 +6,7 @@ PROGRAM_EXEC=./par
 ARGS=sinus 1001 1 .01 1 1
 
 #mpirun -np $NUM_PROCESSES ./par sinus 100 1 .01 1 1
-mpirun -np $NUM_PROCESSES ./par sinus 3 1 .01 1 1
+mpirun -np $NUM_PROCESSES ./par sinus 50 1 .01 1 1
 #mpirun -np $NUM_PROCESSES $PROGRAM_EXEC $ARGS
 #mpirun -np $NUM_PROCESSES --mca pls_rsh_agent $RSH_AGENT \
 #    --hostfile $MPI_HOSTFILE $PROGRAM_EXEC