From ba71ee6707dda7485c9dcf1a03cee54c1d382bd8 Mon Sep 17 00:00:00 2001
From: josh <josh@45c1a28c-8058-47b2-ae61-ca45b979098e>
Date: Sat, 27 Sep 2008 15:37:25 +0000
Subject: [PATCH] added return value information to threads and synchronized
 maximum values in main thread after joining worker threads

git-svn-id: svn://anubis/gvsu@178 45c1a28c-8058-47b2-ae61-ca45b979098e
---
 cs677/pa2/threaded.cc | 53 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 11 deletions(-)

diff --git a/cs677/pa2/threaded.cc b/cs677/pa2/threaded.cc
index f530c88..028e48d 100644
--- a/cs677/pa2/threaded.cc
+++ b/cs677/pa2/threaded.cc
@@ -25,6 +25,13 @@ int * matrix;
 vector<char> * s;
 vector<char> * t;
 
+struct retval_t
+{
+    int max_val;
+    int max_i;
+    int max_j;
+} retval;
+
 /* Print basic usage information */
 void usage(char * prog)
 {
@@ -106,13 +113,34 @@ int main(int argc, char * argv[])
         }
     }
 
+    int max_val = 0, max_i = 0, max_j = 0;
     for (int i = 0; i < num_threads; i++)
     {
-        pthread_join(threads[i], NULL);
+        struct retval_t * retval;
+        pthread_join(threads[i], (void **) &retval);
+        if (retval->max_val == max_val)
+        {
+            if ( (retval->max_i + retval->max_j) > (max_i + max_j) )
+            {
+                max_i = retval->max_i;
+                max_j = retval->max_j;
+            }
+        }
+        else if (retval->max_val > max_val)
+        {
+            max_val = retval->max_val;
+            max_i = retval->max_i;
+            max_j = retval->max_j;
+        }
+        delete retval;
     }
 
-    pthread_barrier_destroy(&barrier);
+    /* Print the maximum value and position */
+    cout << "Maximum value is " << max_val << " at position ("
+        << max_i << ", " << max_j << ")" << endl;
 
+    /* Clean up after ourselves */
+    pthread_barrier_destroy(&barrier);
     delete[] matrix;
     delete[] threads;
     return 0;
@@ -144,7 +172,7 @@ void * calcSimMatrixThread(void * arg)
     int t_size = t->size();
     int last_step = s_size + t_size;
     int (*F)[s_size+1][t_size+1] = (int (*) [s_size+1][t_size+1]) matrix;
-    int max_x = 0, max_y = 0, max_val = 0;
+    int max_i = 0, max_j = 0, max_val = 0;
     int first_task_id, num_tasks;
     taskAllocate(t_size+1, num_threads, id, &first_task_id, &num_tasks);
     for (int i = 0, idx = first_task_id; i < num_tasks; i++, idx++)
@@ -196,17 +224,17 @@ void * calcSimMatrixThread(void * arg)
             if ((*F)[i][j] > max_val)
             {
                 max_val = (*F)[i][j];
-                max_x = i;
-                max_y = j;
+                max_i = i;
+                max_j = j;
             }
             else if ((*F)[i][j] == max_val)
             {
                 /* If we found a value the same as our current maximum
                  * value, see if it has a greater i+j value */
-                if ( (i + j) > (max_x + max_y) )
+                if ( (i + j) > (max_i + max_j) )
                 {
-                    max_x = i;
-                    max_y = j;
+                    max_i = i;
+                    max_j = j;
                 }
             }
         }
@@ -224,9 +252,12 @@ void * calcSimMatrixThread(void * arg)
         printf("\n");
     }
 #endif
-    cout << "Maximum value is " << max_val << " at position ("
-        << max_x << ", " << max_y << ")" << endl;
+
+    struct retval_t * retval = new struct retval_t;
+    retval->max_val = max_val;
+    retval->max_i = max_i;
+    retval->max_j = max_j;
 
     delete realarg;
-    return NULL;
+    return retval;
 }