From 43a5b30712cae6de73517a394040f8950a082e50 Mon Sep 17 00:00:00 2001
From: josh <josh@45c1a28c-8058-47b2-ae61-ca45b979098e>
Date: Sun, 23 Nov 2008 03:23:55 +0000
Subject: [PATCH] first attempt completed, needs rework to receive multiple
 columns

git-svn-id: svn://anubis/gvsu@245 45c1a28c-8058-47b2-ae61-ca45b979098e
---
 cs677/hw4/src/transpose.cc | 41 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/cs677/hw4/src/transpose.cc b/cs677/hw4/src/transpose.cc
index c694f97..f991287 100644
--- a/cs677/hw4/src/transpose.cc
+++ b/cs677/hw4/src/transpose.cc
@@ -44,6 +44,7 @@ int main(int argc, char * argv[])
     MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
     MPI_Comm_size(MPI_COMM_WORLD, &p);
 
+#if 0
     for (int i = 0; i < argc; i++)
     {
         if (!strncmp(argv[i], "-s", 2))
@@ -53,8 +54,13 @@ int main(int argc, char * argv[])
                                : argv[++i]);
         }
     }
+#endif
 
+    /* Initialize the matrix */
     int matrix[n][n];
+    for (int i = 0; i < n; i++)
+        for (int j = 0; j < n; j++)
+            matrix[i][j] = 0;
     int my_first_row;
     int my_num_rows;
     taskAllocate(n, p, my_rank, &my_first_row, &my_num_rows);
@@ -66,6 +72,41 @@ int main(int argc, char * argv[])
         }
     }
 
+    /* Populate the displacements array */
+    int displs[p];
+    int counts[p];
+    for (int i = 0, total = 0; i < p; i++)
+    {
+        int first;
+        int count;
+        taskAllocate(n, p, i, &first, &count);
+        displs[i] = total;
+        count[i] = count;
+        total += count;
+    }
+
+    /* Transpose the matrix with p gather operations */
+    int recvbuf[p];
+    for (int i = 0; i < p; i++)
+    {
+        int col_i_vals_for_proc_p[my_num_rows];
+        for (int row_offset = 0; row_offset < my_num_rows; row_offset++)
+        {
+            col_i_vals_for_proc_p[row_offset] =
+                matrix[my_first_row + row_offset][i];
+        }
+        MPI_Gatherv(&col_i_vals_for_proc_p[0], my_num_rows, MPI_INT,
+                    &recvbuf[0], &counts[0], &displs[0],
+                    MPI_INT, MPI_COMM_WORLD);
+    }
+
+    /* Put my received entries into my columns of the matrix */
+    for (int i = 0; i < p; i++)
+    {
+        matrix[i][p] = recvbuf[i];
+    }
+
+    /* Print out the final matrix */
     if (my_rank == 0)
     {
         cout << "Final matrix:" << endl;