Commit ae3bde0a authored by Pedro Gonnet's avatar Pedro Gonnet
Browse files

fixed a silly inefficiency that made scheduler_ranktasks run in o(n^2) instead of o(n).

parent 898d3ae6
......@@ -768,47 +768,49 @@ void scheduler_ranktasks(struct scheduler *s) {
/* Run through the tasks and get all the waits right. */
for (int k = 0; k < nr_tasks; k++) {
tid[k] = k;
for (int j = 0; j < tasks[k].nr_unlock_tasks; j++)
tasks[k].unlock_tasks[j]->wait += 1;
}
/* Load the tids of tasks with no waits. */
int left = 0;
for (int k = 0; k < nr_tasks; k++)
if (tasks[k].wait == 0) {
tid[left] = k;
left += 1;
}
/* Main loop. */
for (int j = 0, rank = 0, left = 0; left < nr_tasks; rank++) {
/* Load the tids of tasks with no waits. */
for (int k = left; k < nr_tasks; k++)
if (tasks[tid[k]].wait == 0) {
int temp = tid[j];
tid[j] = tid[k];
tid[k] = temp;
j += 1;
}
for (int j = 0, rank = 0; left < nr_tasks; rank++) {
/* Did we get anything? */
if (j == left) error("Unsatisfiable task dependencies detected.");
const int left_old = left;
/* Unlock the next layer of tasks. */
for (int i = left; i < j; i++) {
struct task *t = &tasks[tid[i]];
for (; j < left_old; j++) {
struct task *t = &tasks[tid[j]];
t->rank = rank;
tid[i] = t - tasks;
if (tid[i] >= nr_tasks) error("Task index overshoot.");
/* message( "task %i of type %s has rank %i." , i ,
(t->type == task_type_self) ? "self" : (t->type == task_type_pair) ?
"pair" : "sort" , rank ); */
for (int k = 0; k < t->nr_unlock_tasks; k++)
t->unlock_tasks[k]->wait -= 1;
for (int k = 0; k < t->nr_unlock_tasks; k++) {
struct task *u = t->unlock_tasks[k];
if (--u->wait == 0) {
tid[left] = u - tasks;
left += 1;
}
}
}
/* The new left (no, not tony). */
left = j;
/* Move back to the old left (like Sanders). */
j = left_old;
}
/* Verify that the tasks were ranked correctly. */
/* for ( k = 1 ; k < s->nr_tasks ; k++ )
if ( tasks[ tid[k-1] ].rank > tasks[ tid[k-1] ].rank )
error( "Task ranking failed." ); */
for (int k = 1; k < s->nr_tasks; k++)
if (tasks[tid[k - 1]].rank > tasks[tid[k - 1]].rank)
error("Task ranking failed.");
}
/**
......
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