Added comment and moved magic value to constant

game_of_life/main.c

+/**
+ * Author: Baptiste Coudray
+ * School: HEPIA
+ * Class: ITI-3
+ * Year 2020-2021
+ */
+
 #include <stdio.h>
 #include <stdint.h>
 #include <mpi.h>
@@ -28,14 +35,8 @@
 
 #define CHUNK_BOARD_TAG 8
 
-//void printChunkBoard(int8_t *chunkBoard, int n1, int n2) {
-//    for (int i = 0; i < n1; ++i) {
-//        for (int j = 0; j < n2; ++j) {
-//            printf("%d ", chunkBoard[INDEX_2D_TO_1D(i, j, n2)]);
-//        }
-//        printf("\n");
-//    }
-//}
+#define ROOT_RANK 0
+#define FPS 60
 
 int createGridCommunicators(MPI_Comm *cartComm, MPI_Comm *rowComm, MPI_Comm *colComm, int nProc) {
     int gridN = (int) sqrt(nProc);
@@ -148,6 +149,7 @@ void shareAndBuildEnvelope(int8_t *chunkBoardMyEnvelope, int8_t *chunkBoardEnvel
 
         MPI_Isend(chunkBoardMyEnvelopeNorthEast, 1, MPI_INT8_T, destSource, NORTH_EAST_CELL_TAG, MPI_COMM_WORLD,
                   &requests[iRequest++]);
+        /* Neighbour send south-west cell, which correspond to north-east cell */
         MPI_Irecv(&missingCells[1], 1, MPI_INT8_T, destSource, SOUTH_WEST_CELL_TAG, MPI_COMM_WORLD,
                   &requests[iRequest++]);
     }
@@ -161,6 +163,7 @@ void shareAndBuildEnvelope(int8_t *chunkBoardMyEnvelope, int8_t *chunkBoardEnvel
 
         MPI_Isend(chunkBoardMyEnvelopeSouthEast, 1, MPI_INT8_T, destSource, SOUTH_EAST_CELL_TAG, MPI_COMM_WORLD,
                   &requests[iRequest++]);
+        /* Neighbour send north-west cell, which correspond to south-east cell */
         MPI_Irecv(&missingCells[2], 1, MPI_INT8_T, destSource, NORTH_WEST_CELL_TAG, MPI_COMM_WORLD,
                   &requests[iRequest++]);
     }
@@ -174,6 +177,7 @@ void shareAndBuildEnvelope(int8_t *chunkBoardMyEnvelope, int8_t *chunkBoardEnvel
 
         MPI_Isend(chunkBoardMyEnvelopeSouthWest, 1, MPI_INT8_T, destSource, SOUTH_WEST_CELL_TAG, MPI_COMM_WORLD,
                   &requests[iRequest++]);
+        /* Neighbour send north-east cell, which correspond to south-west cell */
         MPI_Irecv(&missingCells[3], 1, MPI_INT8_T, destSource, NORTH_EAST_CELL_TAG, MPI_COMM_WORLD,
                   &requests[iRequest++]);
     }
@@ -187,12 +191,14 @@ void shareAndBuildEnvelope(int8_t *chunkBoardMyEnvelope, int8_t *chunkBoardEnvel
 
         MPI_Isend(chunkBoardMyEnvelopeNorthWest, 1, MPI_INT8_T, destSource, NORTH_WEST_CELL_TAG, MPI_COMM_WORLD,
                   &requests[iRequest++]);
+        /* Neighbour send south-east cell, which correspond to north-west cell */
         MPI_Irecv(&missingCells[0], 1, MPI_INT8_T, destSource, SOUTH_EAST_CELL_TAG, MPI_COMM_WORLD,
                   &requests[iRequest]);
     }
 
     MPI_Waitall(16, requests, MPI_STATUSES_IGNORE);
 
+    /* Copy missing cells into the envelope */
     chunkBoardEnvelope[INDEX_2D_TO_1D(NORTH_INDEX, chunkN, chunkM)] = chunkBoardEnvelope[INDEX_2D_TO_1D(
             EAST_INDEX, 0, chunkM)] = missingCells[1];
     chunkBoardEnvelope[INDEX_2D_TO_1D(SOUTH_INDEX, chunkN, chunkM)] = chunkBoardEnvelope[INDEX_2D_TO_1D(EAST_INDEX,
@@ -246,12 +252,12 @@ int main(int argc, char *argv[]) {
     struct futhark_context *futharkContext = futhark_context_new(contextConfig);
 
     /* GFX Initialization */
-    struct gfx_context_t *gfxContext = myRank == 0 ? gfx_create("Game of Life", BOARD_N, BOARD_N) : NULL;
-    if (myRank == 0 && !gfxContext) {
+    struct gfx_context_t *gfxContext = myRank == ROOT_RANK ? gfx_create("Game of Life", BOARD_N, BOARD_N) : NULL;
+    if (myRank == ROOT_RANK && !gfxContext) {
         fprintf(stderr, "Graphic mode initialization failed!\n");
         return EXIT_FAILURE;
     }
-    if (myRank == 0) {
+    if (myRank == ROOT_RANK) {
         SDL_ShowCursor(SDL_ENABLE);
     }
 
@@ -261,7 +267,7 @@ int main(int argc, char *argv[]) {
     int chunkM = chunkN + 2;
     int *indexes = divideBoard(BOARD_N, chunkN, nProc);
 
-    int8_t *board = myRank == 0 ? calloc(BOARD_N * BOARD_N, sizeof(int8_t)) : NULL;
+    int8_t *board = myRank == ROOT_RANK ? calloc(BOARD_N * BOARD_N, sizeof(int8_t)) : NULL;
     int8_t *chunkBoard = calloc((size_t) chunkNN, sizeof(int8_t));
     int8_t *chunkBoardMyEnvelope = calloc(((size_t) (4 * chunkN)), sizeof(int8_t));
     int8_t *chunkBoardEnvelope = calloc(((size_t) (4 * chunkM)), sizeof(int8_t));
@@ -289,7 +295,7 @@ int main(int argc, char *argv[]) {
         futhark_values_i8_2d(futharkContext, futNextChunkBoard, chunkBoard);
         futhark_context_sync(futharkContext);
 
-        if (myRank == 0) {
+        if (myRank == ROOT_RANK) {
             chunkBoardToBoard(board, BOARD_N, chunkBoard, chunkN, indexes, myRank);
             int8_t *tmpChunkBoard = calloc((size_t) chunkNN, sizeof(int8_t));
             MPI_Status status = {0};
@@ -299,10 +305,10 @@ int main(int argc, char *argv[]) {
             }
             free(tmpChunkBoard);
         } else {
-            MPI_Send(chunkBoard, chunkNN, MPI_INT8_T, 0, CHUNK_BOARD_TAG, MPI_COMM_WORLD);
+            MPI_Send(chunkBoard, chunkNN, MPI_INT8_T, ROOT_RANK, CHUNK_BOARD_TAG, MPI_COMM_WORLD);
         }
 
-        if (myRank == 0) {
+        if (myRank == ROOT_RANK) {
             SDL_PumpEvents();
             SDL_Event event;
             SDL_PollEvent(&event);
@@ -326,8 +332,8 @@ int main(int argc, char *argv[]) {
         futhark_free_i8_2d(futharkContext, futChunkBoardEnvelope);
         futhark_free_i8_2d(futharkContext, futNextChunkBoard);
 
-        MPI_Bcast(&exit, 1, MPI_C_BOOL, 0, MPI_COMM_WORLD);
-        usleep(16666);
+        MPI_Bcast(&exit, 1, MPI_C_BOOL, ROOT_RANK, MPI_COMM_WORLD);
+        usleep(1000000 / FPS);
     }
 
     free(indexes);
@@ -335,7 +341,7 @@ int main(int argc, char *argv[]) {
     free(chunkBoardEnvelope);
     free(chunkBoardMyEnvelope);
 
-    if (myRank == 0) {
+    if (myRank == ROOT_RANK) {
         free(board);
         gfx_destroy(gfxContext);
     }