improve randomization

[c11tester.git] / schedule.cc

diff --git a/schedule.cc b/schedule.cc
index 2ef4c4d2f968ef2c97dffbf8f17a3e80c447c9cd..2a02e307cf69f3a6a35058254bcafd046300645e 100644 (file)
--- a/schedule.cc
+++ b/schedule.cc
@@ -214,8 +214,6 @@ void Scheduler::wake(Thread *t)
  */
 Thread * Scheduler::select_next_thread(Node *n)
 {
-       int old_curr_thread = curr_thread_index;
-
        bool have_enabled_thread_with_priority = false;
        if (model->params.fairwindow != 0) {
                for (int i = 0; i < enabled_len; i++) {
@@ -228,8 +226,17 @@ Thread * Scheduler::select_next_thread(Node *n)
                }
        }       
 
-       for (int i = 0; i < enabled_len; i++) {
-               curr_thread_index = (old_curr_thread + i + 1) % enabled_len;
+       int avail_threads = enabled_len;        // number of available threads
+       int thread_list[enabled_len];   // keep a list of threads to select from
+       for (int i = 0; i< enabled_len; i++){
+               thread_list[i] = i;
+       }
+
+       while (avail_threads > 0) {
+               int random_index = rand() % avail_threads;
+               curr_thread_index = thread_list[random_index];  // randomly select a thread from available threads
+               
+               // curr_thread_index = (curr_thread_index + i + 1) % enabled_len;
                thread_id_t curr_tid = int_to_id(curr_thread_index);
                if (model->params.yieldon) {
                        bool bad_thread = false;
@@ -240,13 +247,20 @@ Thread * Scheduler::select_next_thread(Node *n)
                                        break;
                                }
                        }
-                       if (bad_thread)
+                       if (bad_thread) {
+                               thread_list[random_index] = thread_list[avail_threads - 1]; // remove this threads from available threads 
+                               avail_threads--;
+
                                continue;
+                       }
                }
                
                if (enabled[curr_thread_index] == THREAD_ENABLED &&
                                (!have_enabled_thread_with_priority || n->has_priority(curr_tid))) {
                        return model->get_thread(curr_tid);
+               } else {        // remove this threads from available threads 
+                       thread_list[random_index] = thread_list[avail_threads - 1]; 
+                       avail_threads--;
                }
        }