if (read != thrd_last_read_act[thread_id]) {
FuncNode * func_node = history->get_curr_func_node(tid);
Predicate * curr_pred = func_node->get_predicate_tree_position(tid);
+
FuncInst * read_inst = func_node->get_inst(read);
Predicate * selected_branch = selectBranch(tid, curr_pred, read_inst);
// No write satisfies the selected predicate, so pause this thread.
while ( rf_set->size() == 0 ) {
Thread * read_thread = execution->get_thread(tid);
+ Predicate * selected_branch = get_selected_child_branch(tid);
+ bool should_reselect_predicate = false;
//model_print("the %d read action of thread %d at %p is unsuccessful\n", read->get_seq_number(), read_thread->get_id(), read->get_location());
- if (find_threads(read)) {
+ if (!find_threads(read)) {
+ update_predicate_score(selected_branch, SLEEP_FAIL_TYPE1);
+ should_reselect_predicate = true;
+ } else if (!should_conditional_sleep(selected_branch)) {
+ update_predicate_score(selected_branch, SLEEP_FAIL_TYPE2);
+ should_reselect_predicate = true;
+ } else {
// reset thread pending action and revert sequence numbers
read_thread->set_pending(read);
read->reset_seq_number();
execution->restore_last_seq_num();
conditional_sleep(read_thread);
-
// Returning -1 stops the while loop of ModelExecution::process_read
return -1;
- } else {
- Predicate * selected_branch = get_selected_child_branch(tid);
- failed_predicates.put(selected_branch, true);
+ }
+ if (should_reselect_predicate) {
SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
for (uint i = 0; i < pruned_writes->size(); i++) {
rf_set->push_back( (*pruned_writes)[i] );
ModelVector<Predicate *> * children = curr_pred->get_children();
SnapVector<Predicate *> branches;
+ uint32_t numerator = 1;
for (uint i = 0; i < children->size(); i++) {
Predicate * child = (*children)[i];
if (child->get_func_inst() == read_inst && !failed_predicates.contains(child)) {
branches.push_back(child);
+
+ // max of (exploration counts + 1)
+ if (child->get_expl_count() + 1 > numerator)
+ numerator = child->get_expl_count() + 1;
}
}
}
// randomly select a branch
- int random_index = random() % branches.size();
- Predicate * random_branch = branches[ random_index ];
+ // int random_index = random() % branches.size();
+ // Predicate * random_branch = branches[ random_index ];
+
+ int index = choose_index(&branches, numerator);
+ Predicate * random_branch = branches[ index ];
thrd_selected_child_branch[thread_id] = random_branch;
+ // Update predicate tree position
+ FuncNode * func_node = history->get_curr_func_node(tid);
+ func_node->set_predicate_tree_position(tid, random_branch);
+
return random_branch;
}
+/**
+ * @brief Select a branch from the given predicate branches based
+ * on their exploration counts.
+ *
+ * Let b_1, ..., b_n be branches with exploration counts c_1, ..., c_n
+ * M := max(c_1, ..., c_n) + 1
+ * Factor f_i := M / (c_i + 1)
+ * The probability p_i that branch b_i is selected:
+ * p_i := f_i / (f_1 + ... + f_n)
+ * = \fraction{ 1/(c_i + 1) }{ 1/(c_1 + 1) + ... + 1/(c_n + 1) }
+ *
+ * Note: (1) c_i + 1 is used because counts may be 0.
+ * (2) The numerator of f_i is chosen to reduce the effect of underflow
+ *
+ * @param numerator is M defined above
+ */
+int NewFuzzer::choose_index(SnapVector<Predicate *> * branches, uint32_t numerator)
+{
+ if (branches->size() == 1)
+ return 0;
+
+ double total_factor = 0;
+ SnapVector<double> factors = SnapVector<double>( branches->size() + 1 );
+ for (uint i = 0; i < branches->size(); i++) {
+ Predicate * branch = (*branches)[i];
+ double factor = (double) numerator / (branch->get_expl_count() + 5 * branch->get_fail_count() + 1);
+ total_factor += factor;
+ factors.push_back(factor);
+ }
+
+ double prob = (double) random() / RAND_MAX;
+ double prob_sum = 0;
+ int index = 0;
+
+ for (uint i = 0; i < factors.size(); i++) {
+ index = i;
+ prob_sum += (double) (factors[i] / total_factor);
+ if (prob_sum > prob) {
+ break;
+ }
+ }
+
+ return index;
+}
+
Predicate * NewFuzzer::get_selected_child_branch(thread_id_t tid)
{
int thread_id = id_to_int(tid);
/* history->add_waiting_thread is already called in find_threads */
}
+bool NewFuzzer::should_conditional_sleep(Predicate *)
+{
+ return true;
+}
+
bool NewFuzzer::has_paused_threads()
{
return paused_thread_list.size() != 0;
history->remove_waiting_write(tid);
history->remove_waiting_thread(tid);
- //model_print("thread %d is woken up\n", tid);
threadlist[*numthreads] = tid;
(*numthreads)++;
+
+ Predicate * selected_branch = get_selected_child_branch(tid);
+ update_predicate_score(selected_branch, SLEEP_FAIL_TYPE3);
+
+ model_print("thread %d is woken up\n", tid);
}
/* Wake up conditional sleeping threads if the desired write is available */
thread_id_t tid = thread->get_id();
history->remove_waiting_write(tid);
history->remove_waiting_thread(tid);
+
+ Predicate * selected_branch = get_selected_child_branch(tid);
+ update_predicate_score(selected_branch, SLEEP_SUCCESS);
+
+ model_print("** thread %d is woken up\n", tid);
}
/* Find threads that may write values that the pending read action is waiting for
return finds_waiting_for;
}
+/* Update predicate counts and scores (asynchronous) when the read value is not available
+ *
+ * @param type
+ * type 1: find_threads return false
+ * type 2: find_threads return true, but the fuzzer decides that that thread shall not sleep based on sleep score
+ * type 3: threads are put to sleep but woken up before the waited value appears
+ * type 4: threads are put to sleep and the waited vaule appears (success)
+ */
+void NewFuzzer::update_predicate_score(Predicate * predicate, sleep_result_t type)
+{
+ switch (type) {
+ case SLEEP_FAIL_TYPE1:
+ predicate->incr_fail_count();
+
+ /* Do not choose this predicate when reselecting a new branch */
+ failed_predicates.put(predicate, true);
+ break;
+ case SLEEP_FAIL_TYPE2:
+ predicate->incr_fail_count();
+ predicate->decr_sleep_score(1);
+ failed_predicates.put(predicate, true);
+ break;
+ case SLEEP_FAIL_TYPE3:
+ predicate->incr_fail_count();
+ predicate->incr_sleep_score(10);
+ break;
+ case SLEEP_SUCCESS:
+ predicate->decr_sleep_score(10);
+ break;
+ default:
+ model_print("unknown predicate result type.\n");
+ break;
+ }
+}
+
bool NewFuzzer::shouldWait(const ModelAction * act)
{
return random() & 1;
projects / c11tester.git / blobdiff