def check(self,progress):
"""
Parameters
----------
progress : float
The current progress.
Returns
-------
self.difficult : bool
If ``True``, the branch is difficult because the progress rate is
below the threshold.
"""
time_now = time.time()
one_minute = 60 # [s]
if self.time_last is None:
self.time_last = time_now
self.progress_last = progress
else:
if time_now-self.time_last>one_minute:
progress_rate = progress-self.progress_last # [%/min]
self.time_last = time_now
self.progress_last = progress
self.difficult = progress_rate<self.threshold
if self.difficult:
tools.info_print('current branch is difficult')
return self.difficult
def status_publisher_thread(self):
"""Main loop thread which publishes the status."""
while True:
self.publisher_looprate.update()
#-- Main code ---------------------------------------
self.mutex.acquire()
queue_length = len(self.task_queue)
worker_status = copy.deepcopy(self.worker_proc_status)
looprates = dict(
publisher=self.publisher_looprate.get_frequency(),
dispatcher=self.dispatcher_looprate.get_frequency(),
collector=self.collector_looprate.get_frequency())
self.mutex.release()
self.status_publisher.update(worker_status, queue_length,
looprates)
#----------------------------------------------------
self.mutex.acquire()
stop = self.stop_threads
if stop:
self.status_publisher.update(self.worker_proc_status,
len(self.task_queue),
looprates,
force=True)
self.status_publisher.reset_estimators()
self.mutex.release()
if stop:
tools.info_print('status publisher stopping')
return
def offload_child_computation(self,child,location,which_alg,
prioritize_self=False,force='none'):
"""
Offload partitioning for child to another worker process.
Parameters
----------
child : Tree
The child for which computation is to be offloaded.
location : string
Location of the child in the overall tree.
which_alg : {'ecc','lcss'}
Which algorithm is to be run for the partitioning.
prioritize_self : bool, optional
If ``True``, ignore worker count but do respect recursion limit in
terms of assigning work to self.
force : {'none','offload','self'}, optional
'offload' means choose to submit task to queue, no matter what;
'self' means continue to work on task alone, no matter what; 'none'
means no such forcing.
"""
# --- Check worker count
with open(global_vars.IDLE_COUNT_FILE,'rb') as f:
try:
idle_worker_count = pickle.load(f)
except EOFError:
# This may occur if the file is currently being written to by
# the scheduler. In this case, conservatively assume that there
# are no idle workers
idle_worker_count = 0
tools.info_print('idle worker count = %d'%(idle_worker_count))
# --- Check recursion limit
recursion_depth = (len(location)-
len(self.status_publisher.data['current_branch']))
recurs_limit_reached = recursion_depth>global_vars.MAX_RECURSION_LIMIT
if recurs_limit_reached:
tools.error_print('recursion limit reached - submitting task'
' to queue')
# --- Check difficult of current branch
progress = self.status_publisher.data['volume_filled_current']
is_difficult = self.difficulty.check(progress)
# --- Offloading logic
if (force!='self' and
(force=='offload' or recurs_limit_reached or is_difficult or
(idle_worker_count>0 and not prioritize_self))):
new_task = dict(branch_root=child,location=location,
action=which_alg)
tools.info_print('sending task {}'.format(new_task))
tools.MPI.nonblocking_send(new_task,dest=global_vars.SCHEDULER_PROC,
tag=global_vars.NEW_BRANCH_TAG)
else:
self.status_publisher.update(algorithm=which_alg)
self.alg_call(which_alg,child,location)
def update(self,active=None,failed=False,volume_filled_increment=None,simplex_count_increment=None,location=None,algorithm=None):
"""
Update the data.
Parameters
----------
active : bool, optional
``True`` if the process is in the 'active' state.
failed : bool, optional
``True`` if algorithm failed (worker process shutdown)
volume_filled_increment : float, optional
Volume of closed lead.
simplex_count_increment : int, optional
How many additional simplices added to partition.
location : str, optional
Current location in the tree.
algorithm : {'ecc','lcss'}
Which algorithm is to be run for the partitioning.
"""
# Update time counters
dt = time.time()-self.time_previous
self.time_previous += dt
if self.data['status']=='active':
self.data['time_active_total'] += dt
self.data['time_active_current'] += dt
else:
self.data['time_idle'] += dt
if self.data['algorithm']=='ecc':
self.data['time_ecc'] += dt
else:
self.data['time_lcss'] += dt
# Update status
if active is not None:
self.data['status'] = 'active' if active else 'idle'
tools.info_print('sending status update, status = %s'%(self.data['status']))
if failed is True:
self.data['status'] = 'failed'
# Update volume counters
if volume_filled_increment is not None:
self.data['volume_filled_total'] += volume_filled_increment
self.data['volume_filled_current'] += volume_filled_increment/self.volume_current
# Update simplex counters
if simplex_count_increment is not None:
self.data['simplex_count_total'] += simplex_count_increment
self.data['simplex_count_current'] += simplex_count_increment
# Update location
if location is not None:
self.data['current_location'] = location
# Update algorithm
if algorithm is not None:
self.data['algorithm'] = algorithm
self.__write()
def ecc(self,node,location):
"""
Implementation of [1] Algorithm 2 lines 4-16. Pass a tree root
node and this grows the tree until its leaves are feasible partition
cells. **Caution**: modifies ``node`` (passed by reference).
[1] D. Malyuta, B. Acikmese, M. Cacan, and D. S. Bayard,
"Partition-based feasible integer solution pre-computation for hybrid
model predictive control," in 2019 European Control Conference
(accepted), IFAC, jun 2019.
Parameters
----------
node : Tree
Tree root. Sufficient that it just holds node.data.vertices for the
simplex vertices.
location : string
Location in tree of this node. String where '0' at index i means
take left child, '1' at index i means take right child (at depth
value i).
"""
self.status_publisher.update(location=location)
tools.info_print('ecc at location = %s'%(location))
c_R = np.average(node.data.vertices,axis=0) # Simplex barycenter
if not self.oracle.P_theta(theta=c_R,check_feasibility=True):
raise RuntimeError('STOP, Theta contains infeasible regions')
else:
delta_hat,vx_inputs_and_costs = self.oracle.V_R(node.data.vertices)
if delta_hat is None:
S_1,S_2 = tools.split_along_longest_edge(node.data.vertices)[:2]
child_left = NodeData(vertices=S_1)
child_right = NodeData(vertices=S_2)
node.grow(child_left,child_right)
self.status_publisher.update(simplex_count_increment=1)
# Recursive call for each resulting simplex
self.offload_child_computation(node.left,location+'0','ecc')
self.offload_child_computation(node.right,location+'1','ecc',
prioritize_self=True)
else:
# Assign feasible commutation to simplex
Nvx = node.data.vertices.shape[0]
vertex_costs = np.array([vx_inputs_and_costs[i][1]
for i in range(Nvx)])
vertex_inputs = np.array([vx_inputs_and_costs[i][0]
for i in range(Nvx)])
node.data = NodeData(vertices=node.data.vertices,
commutation=delta_hat,
vertex_costs=vertex_costs,
vertex_inputs=vertex_inputs)
self.offload_child_computation(node,location,'lcss',
force='self')
def __publish_idle_count(self):
"""
Communicate to worker processes how many more workers are idle than
there are tasks in the queue. If there are more workers idle then
there are tasks in the queue, we want currently active workers to
offload some of their work to these "slacking" workers.
**NOT THREAD SAFE -- wrap with a mutex!**
"""
num_tasks = len(self.task_queue)
num_idle_workers = len(self.idle_workers)
num_workers_with_no_work = max(num_idle_workers - num_tasks, 0)
tools.info_print('idle worker count = %d' % (num_idle_workers))
with open(global_vars.IDLE_COUNT_FILE, 'wb') as f:
pickle.dump(num_workers_with_no_work, f)
def work_dispatcher_thread(self):
"""Main loop thread which dispatches tasks to workers."""
while True:
self.dispatcher_looprate.update()
#-- Main code ---------------------------------------
# Dispatch work to idle workers
worker_count_changed = False
while True:
# Check exit condition
self.mutex.acquire()
num_tasks = len(self.task_queue)
num_idle_workers = len(self.idle_workers)
self.mutex.release()
if num_tasks == 0 or num_idle_workers == 0:
break
# Dispatch task to idle worker process
self.mutex.acquire()
task = self.task_queue.pop()
idle_worker_idx = self.idle_workers.pop()
self.mutex.release()
tools.info_print(('dispatching task to worker (%d) (%d '
'tasks left), data {}' %
(self.get_worker_proc_num(idle_worker_idx),
num_tasks - 1)).format(task))
self.mutex.acquire()
tools.MPI.blocking_send(
task,
dest=self.get_worker_proc_num(idle_worker_idx),
tag=global_vars.NEW_WORK_TAG)
self.mutex.release()
self.mutex.acquire()
self.worker2task[idle_worker_idx] = task
self.mutex.release()
worker_count_changed = True
if worker_count_changed:
self.mutex.acquire()
self.__publish_idle_count()
self.mutex.release()
#----------------------------------------------------
self.mutex.acquire()
stop = self.stop_threads
self.mutex.release()
if stop:
tools.info_print('work dispatcher stopping')
return
def setup(self):
# Optimization problem oracle
suboptimality_settings = tools.MPI.broadcast(None,root=global_vars.SCHEDULER_PROC)
self.oracle = example(abs_err=suboptimality_settings['abs_err'],
rel_err=suboptimality_settings['rel_err'])[2]
tools.info_print('made oracle')
# Checker whether a branch is "difficult"
self.difficulty = DifficultyChecker()
# Status publisher
self.status_publisher = WorkerStatusPublisher()
tools.MPI.global_sync() # wait for all slaves to setup
# Algorithm call selector
def alg_call(which_alg,branch,location):
if which_alg=='ecc':
return self.ecc(branch,location)
else:
return self.lcss(branch,location)
self.alg_call = alg_call
def spin(self):
"""
A loop which waits (by passive blocking) for the roots of a new branch
to partition to be received from the scheduler process. When received,
the branch is partitioned. When done, the partitioned branch ("grown
tree") is sent back to the scheduler. The scheduler is responsible for
aborting this loop.
"""
while True:
# Block until new data is received from scheduler
tools.info_print('waiting for data')
data = tools.MPI.blocking_receive(source=global_vars.SCHEDULER_PROC,
tag=global_vars.NEW_WORK_TAG)
tools.info_print('received data {}'.format(data))
if data['action']=='stop':
# Request from scheduler to stop
return
else:
tools.info_print('got branch at location = %s'%
(data['location']))
self.status_publisher.update(active=True)
# Get data about the branch to be worked on
branch = data['branch_root']
branch_location = data['location']
self.status_publisher.set_new_root_simplex(branch.data.vertices,
branch_location,
data['action'])
# Do work on this branch (i.e. partition this simplex)
try:
tools.info_print('calling algorithm')
self.difficulty.reset() # Reset difficult checking
self.alg_call(data['action'],branch,branch_location)
except:
self.status_publisher.update(failed=True)
raise
# Save completed branch and notify scheduler that it is
# available
with open(global_vars.DATA_DIR+'/branch_%s.pkl'%
(data['location']),'wb') as f:
pickle.dump(data,f)
tools.info_print('completed task at location = %s, '
'notifying scheduler'%(data['location']))
self.status_publisher.update(active=False)
def work_collector_thread(self):
"""Main loop thread which collects new and finished tasks from
workers. This thread also evaluates the stopping criterion."""
while True:
self.collector_looprate.update()
#-- Main code ---------------------------------------
# Capture finished workers that are now idle
any_workers_became_idle = False
for i in self.worker_idxs:
self.mutex.acquire()
status = self.status_msg[i].receive()
self.mutex.release()
if status is not None:
tools.info_print(
('got status update from worker (%d), '
'status {}' %
(self.get_worker_proc_num(i))).format(status))
self.mutex.acquire()
self.worker_proc_status[i] = status
self.mutex.release()
if status['status'] == 'idle':
self.mutex.acquire()
self.idle_workers.append(i)
if self.worker2task[i] is not None:
self.worker2task[i] = None # reset
self.mutex.release()
any_workers_became_idle = True
# Collect any new work from workers
new_tasks_available = False
for i in self.worker_idxs:
self.mutex.acquire()
task = self.task_msg[i].receive()
self.mutex.release()
if task is not None:
tools.info_print(
('received new task from worker (%d), '
'task {}' %
(self.get_worker_proc_num(i))).format(task))
self.mutex.acquire()
# Inserting at the front naturally "bubbles" the easier
# tasks to the top, while the difficult tasks gather at the
# beginning of self.task_queue
self.task_queue.insert(0, task)
self.mutex.release()
new_tasks_available = True
if any_workers_became_idle or new_tasks_available:
self.mutex.acquire()
self.__publish_idle_count()
self.mutex.release()
#----------------------------------------------------
self.mutex.acquire()
self.stop_threads = (len(self.idle_workers) == self.N_workers
and len(self.task_queue) == 0)
stop = self.stop_threads
self.mutex.release()
if stop:
tools.info_print('work collector is stopping')
return
def spin(self):
"""
Manages worker processes until the partitioning process is finished,
then shuts the processes down and exits.
"""
tools.info_print('creating the main loop threads')
publisher = threading.Thread(target=self.status_publisher_thread)
dispatcher = threading.Thread(target=self.work_dispatcher_thread)
collector = threading.Thread(target=self.work_collector_thread)
tools.info_print('starting the main loop threads...')
collector.start()
dispatcher.start()
publisher.start()
tools.info_print('waiting for the main loop threads to finish...')
collector.join()
dispatcher.join()
publisher.join()
tools.info_print('all main loop threads finished')
