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/*************************************************************************
* Copyright (C) 2009-2014 Tavian Barnes <tavianator@tavianator.com> *
* *
* This file is part of The Dimension Library. *
* *
* The Dimension Library is free software; you can redistribute it and/ *
* or modify it under the terms of the GNU Lesser General Public License *
* as published by the Free Software Foundation; either version 3 of the *
* License, or (at your option) any later version. *
* *
* The Dimension Library is distributed in the hope that it will be *
* useful, but WITHOUT ANY WARRANTY; without even the implied warranty *
* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
* Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public *
* License along with this program. If not, see *
* <http://www.gnu.org/licenses/>. *
*************************************************************************/
/**
* @file
* Future objects.
*/
#include "dimension-internal.h"
#include <pthread.h>
/**
* Since C doesn't support anything like C++'s mutable, we fake it by casting
* away the constness. This is okay since all valid dmnsn_futures live on the
* heap, so cannot be const.
*/
#define MUTATE(future) ((dmnsn_future *)(future))
/* Allocate a new dmnsn_future* */
dmnsn_future *
dmnsn_new_future(void)
{
dmnsn_future *future = DMNSN_MALLOC(dmnsn_future);
future->progress = 0;
future->total = 1;
dmnsn_initialize_mutex(&future->mutex);
dmnsn_initialize_cond(&future->cond);
future->min_wait = 1.0;
future->nthreads = future->nrunning = 1;
future->npaused = 0;
dmnsn_initialize_cond(&future->none_running_cond);
dmnsn_initialize_cond(&future->all_running_cond);
dmnsn_initialize_cond(&future->resume_cond);
return future;
}
static void
dmnsn_delete_future(dmnsn_future *future)
{
if (future) {
dmnsn_destroy_cond(&future->resume_cond);
dmnsn_destroy_cond(&future->all_running_cond);
dmnsn_destroy_cond(&future->none_running_cond);
dmnsn_destroy_cond(&future->cond);
dmnsn_destroy_mutex(&future->mutex);
dmnsn_free(future);
}
}
/* Join the worker thread and delete `future'. */
int
dmnsn_future_join(dmnsn_future *future)
{
void *ptr;
int retval = -1;
if (future) {
dmnsn_assert(future->npaused == 0, "Attempt to join future while paused");
/* Get the thread's return value */
dmnsn_join_thread(future->thread, &ptr);
if (ptr && ptr != PTHREAD_CANCELED) {
retval = *(int *)ptr;
dmnsn_free(ptr);
}
/* Free the future object */
dmnsn_delete_future(future);
}
return retval;
}
/* Cancel a background thread */
void
dmnsn_future_cancel(dmnsn_future *future)
{
pthread_cancel(future->thread);
}
/**
* Get the current progress, without locking anything.
*
* future->mutex must be locked for this call to be safe.
*/
static inline double
dmnsn_future_progress_unlocked(const dmnsn_future *future)
{
return (double)future->progress/future->total;
}
/* Get the current progress of the worker thread, in [0.0, 1.0] */
double
dmnsn_future_progress(const dmnsn_future *future)
{
dmnsn_future *mfuture = MUTATE(future);
double progress;
dmnsn_lock_mutex(&mfuture->mutex);
progress = dmnsn_future_progress_unlocked(mfuture);
dmnsn_unlock_mutex(&mfuture->mutex);
return progress;
}
/* Find out whether the task is complete. */
bool
dmnsn_future_is_done(const dmnsn_future *future)
{
dmnsn_future *mfuture = MUTATE(future);
bool result;
dmnsn_lock_mutex(&mfuture->mutex);
result = future->progress == future->total;
dmnsn_unlock_mutex(&mfuture->mutex);
return result;
}
/* Wait until dmnsn_future_progress(future) >= progress */
void
dmnsn_future_wait(const dmnsn_future *future, double progress)
{
dmnsn_future *mfuture = MUTATE(future);
dmnsn_lock_mutex(&mfuture->mutex);
while (dmnsn_future_progress_unlocked(mfuture) < progress) {
/* Set the minimum waited-on value */
if (progress < mfuture->min_wait) {
mfuture->min_wait = progress;
}
dmnsn_cond_wait_safely(&mfuture->cond, &mfuture->mutex);
}
dmnsn_unlock_mutex(&mfuture->mutex);
}
/* Pause all threads working on a future. */
void
dmnsn_future_pause(dmnsn_future *future)
{
dmnsn_lock_mutex(&future->mutex);
while (future->nrunning < future->nthreads) {
dmnsn_cond_wait_safely(&future->all_running_cond, &future->mutex);
}
if (future->npaused++ == 0) {
while (future->nrunning > 0) {
dmnsn_cond_wait_safely(&future->none_running_cond, &future->mutex);
}
}
dmnsn_unlock_mutex(&future->mutex);
}
/* Resume all threads working on a future. */
void
dmnsn_future_resume(dmnsn_future *future)
{
dmnsn_lock_mutex(&future->mutex);
dmnsn_assert(future->npaused > 0,
"dmnsn_future_resume() without matching dmnsn_future_pause()");
if (--future->npaused == 0) {
dmnsn_cond_broadcast(&future->resume_cond);
}
dmnsn_unlock_mutex(&future->mutex);
}
/* Set the total number of loop iterations */
void
dmnsn_future_set_total(dmnsn_future *future, size_t total)
{
dmnsn_lock_mutex(&future->mutex);
future->total = total;
dmnsn_unlock_mutex(&future->mutex);
}
static void
dmnsn_future_increment_cleanup(void *ptr)
{
dmnsn_future *future = ptr;
++future->nrunning;
dmnsn_unlock_mutex_impl(&future->mutex);
}
/* Increment the number of completed loop iterations */
void
dmnsn_future_increment(dmnsn_future *future)
{
/* Allow a thread to be canceled whenever it increments a future object --
this is close to PTHREAD_CANCEL_ASYNCHRONOUS but allows consistent state
on cancellation */
pthread_testcancel();
dmnsn_lock_mutex(&future->mutex);
++future->progress;
if (dmnsn_future_progress_unlocked(future) >= future->min_wait) {
future->min_wait = 1.0;
dmnsn_cond_broadcast(&future->cond);
}
if (future->npaused > 0) {
dmnsn_assert(future->nrunning > 0, "More worker threads than expected");
if (--future->nrunning == 0) {
dmnsn_cond_broadcast(&future->none_running_cond);
}
pthread_cleanup_push(dmnsn_future_increment_cleanup, future);
do {
dmnsn_cond_wait(&future->resume_cond, &future->mutex);
} while (future->npaused > 0);
pthread_cleanup_pop(false);
if (++future->nrunning == future->nthreads) {
dmnsn_cond_broadcast(&future->all_running_cond);
}
}
dmnsn_unlock_mutex(&future->mutex);
}
/* Immediately set to 100% completion */
void
dmnsn_future_finish(dmnsn_future *future)
{
dmnsn_lock_mutex(&future->mutex);
future->progress = future->total;
future->nthreads = future->nrunning = 0;
dmnsn_cond_broadcast(&future->cond);
dmnsn_cond_broadcast(&future->none_running_cond);
dmnsn_cond_broadcast(&future->all_running_cond);
dmnsn_unlock_mutex(&future->mutex);
}
/* Set the number of threads */
void
dmnsn_future_set_nthreads(dmnsn_future *future, unsigned int nthreads)
{
dmnsn_lock_mutex(&future->mutex);
dmnsn_assert(future->nrunning == future->nthreads,
"dmnsn_future_set_nthreads() called with paused threads");
future->nthreads = future->nrunning = nthreads;
dmnsn_unlock_mutex(&future->mutex);
}
/* Notify completion of a worker thread */
void
dmnsn_future_finish_thread(dmnsn_future *future)
{
dmnsn_lock_mutex(&future->mutex);
dmnsn_assert(future->nthreads > 0,
"dmnsn_future_finish_thread() called with no threads");
--future->nthreads;
dmnsn_assert(future->nrunning > 0,
"dmnsn_future_finish_thread() called with no running threads");
if (--future->nrunning == 0) {
dmnsn_cond_broadcast(&future->none_running_cond);
}
dmnsn_unlock_mutex(&future->mutex);
}
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