Question

Pyomo需要解决三层多线程框架底层的优化问题。为了更好地说明这一点，下面显示了一个简化的示例：TopProblem是主线程，它创建了三个MiddleProblem线程；然后，每个MiddleProblem线程都会创建三个BottomProblem线程来解决Pyomo问题。

import threading

from pyomo.environ import *

import pyutilib.subprocess.GlobalData
pyutilib.subprocess.GlobalData.DEFINE_SIGNAL_HANDLERS_DEFAULT = False  # This enables multi-thread for pyomo


class BottomProblem(threading.Thread):

    def __init__(self, i, j):
        threading.Thread.__init__(self)
        self.i = i
        self.j = j

    def run(self):

        model = ConcreteModel()

        model.x = Var([1, 2])
        model.obj = Objective(expr=model.x[1] ** 2 + model.x[2] ** 2)
        model.constraint = Constraint(expr=(self.i + 1) * model.x[1] + (self.j + 1) * model.x[2] == 2)

        opt = SolverFactory('ipopt')
        opt.solve(model)
        print('Solved problem (%d, %d)!' % (self.i, self.j))


class MiddleProblem(threading.Thread):

    def __init__(self, i):
        threading.Thread.__init__(self)
        self.i = i

    def run(self):

        threads = [None, None, None]

        for idx in range(3):
            threads[idx] = BottomProblem(self.i, idx)
            threads[idx].start()

        for idx in range(3):
            threads[idx].join()


class TopProblem(object):

    def run(self):
        top_threads = [None, None, None]

        for idx in range(3):
            top_threads[idx] = MiddleProblem(idx)
            top_threads[idx].start()

        for idx in range(3):
            top_threads[idx].join()


top = TopProblem()
top.run()

这是简化版本，所有其他无关的细节均被省略。（在MiddleProblem层中还需要执行其他一些任务，因此我有必要创建一个三层的多线程框架。）

运行此代码时，发生求解器错误：

ERROR: Solver (ipopt) returned non-zero return code (1)
ERROR: Solver log: Ipopt 3.12.12: /anaconda3/envs/pyomo/bin/ipopt: can't open
    /var/folders/r7/1rbnyqbn1pv0dhb787m40qk50w71fq/T/tmpqtaxc2li.pyomo.nl
Exception in thread Thread-10:
Traceback (most recent call last):
  File "/anaconda3/envs/pyomo/lib/python3.7/threading.py", line 917, in _bootstrap_inner
    self.run()
  File "multithread_pyomo_test.py", line 29, in run
    opt.solve(model)
  File "/anaconda3/envs/pyomo/lib/python3.7/site-packages/pyomo/opt/base/solvers.py", line 600, in solve
    "Solver (%s) did not exit normally" % self.name)
pyutilib.common._exceptions.ApplicationError: Solver (ipopt) did not exit normally

此错误的发生是随机的：有时无错误；有时会出现一些线程错误。

在我看来Pyomo和三层多线程搞砸了。那么正确的方法是什么？

Pyomo的三层多线程

0 个答案: