如何异步中止 docplex 中的求解？

Question

我有 2 个同时使用 docplex 求解运行，我想在另一个求解完成后立即停止其中一个求解。有没有办法结束一个解决方案？

Answer 1

您可以使用 get_cplex() 函数返回的 low-level 引擎对象来执行此操作。这是 Cplex class of the CPLEX Python API. You can install an Aborter into that instance using function use_aborter().

的实例

如果您对所有 Cplex 个实例使用相同的中止器，那么您最终可以调用中止器 abort() 函数来停止所有求解。

请注意，中止请求并不总是立即得到处理。在 CPLEX 引擎确认中止之前可能会有一小段延迟。

Answer 2

谢谢，我能够使用以下代码添加该功能：

from docplex.mp.progress import ProgressListener, ProgressClock
class AutomaticAborter(ProgressListener):
    """ a simple implementation of an automatic search stopper.
    """
    def __init__(self):
        super(AutomaticAborter, self).__init__(ProgressClock.All)
        self.last_obj = None
        self.last_obj_time = None
        self.con = 0
        
    def notify_start(self):
        super(AutomaticAborter, self).notify_start()
        self.last_obj = None
        self.last_obj_time = None    
        self.con = 0
    def is_improving(self, new_obj, eps=1e-4):
        last_obj = self.last_obj
        return last_obj is None or (abs(new_obj- last_obj) >= eps)
            
    def notify_progress(self, pdata):
        super(AutomaticAborter, self).notify_progress(pdata)
        global con_f
        if pdata.has_incumbent and self.is_improving(pdata.current_objective):
            self.last_obj = pdata.current_objective
            self.last_obj_time = pdata.time
            print('----> #new objective={0}, time={1}s'.format(self.last_obj, self.last_obj_time))
        else:
            # a non improving move
            last_obj_time = self.last_obj_time
            this_time = pdata.time
            if last_obj_time is not None:
                self.con=con_f
                if con_f>0:
                    print('!! aborting cplex, con_f >{}'.format(self.con))
                    self.abort()
                else:
                    print('----> running {}'.format(con_f))
con_f=0

solver.add_progress_listener(AutomaticAborter())
solver1.add_progress_listener(AutomaticAborter())

def work(worker_queue, id, stop_event):
    while not stop_event.is_set():

        if id==1:
            work.msol=solver.solve(clean_before_solve=True,log_output=True)
        else:
            work.msol1=solver1.solve(clean_before_solve=True,log_output=True)
        # put worker ID in queue
        if not stop_event.is_set():
            worker_queue.put(id)
        break
# queue for workers
worker_queue = Queue()

# indicator for other threads to stop
stop_event = threading.Event()

# run workers
threads = []
threads.append(Thread(target=work, args=(worker_queue, 1, stop_event)))
threads.append(Thread(target=work, args=(worker_queue, 2, stop_event)))

for thread in threads:
    thread.start()
# this will block until the first element is in the queue
first_finished = worker_queue.get()

print(first_finished, 'was first!')

con_f=1


# signal the rest to stop working
stop_event.set()```

如何异步中止 docplex 中的求解？

How to asynchronously abort a solve in docplex?

python

docplex