我实现了 scipy.optimize.minimize,以最小化具有 128 个值的一维数组的 pandas 数据帧的增量值的平均值。
它似乎可以运行并执行一些操作,但它不会停止在 maxiter
处,也不会停止在取自另一个 Stack Overflow 问题的回调函数处。
我的代码是:
import numpy as np
from scipy.optimize import minimize, rosen
import time
import warnings
class TookTooLong(Warning):
pass
class MinimizeStopper(object):
def __init__(self, max_sec=60*60*5):
self.max_sec = max_sec
self.start = time.time()
def __call__(self, xk=None):
elapsed = time.time() - self.start
if elapsed > self.max_sec:
warnings.warn("Terminating optimization: time limit reached",
TookTooLong)
else:
# you might want to report other stuff here
print("Elapsed: %.3f sec" % elapsed)
import scipy.optimize
res = scipy.optimize.minimize(minFunct,oned,options=
{"disp":True,"maxiter":100},tol=0.01,
method ="BFGS",callback=MinimizeStopper(1E-3))
一段时间后显示的消息告诉我已经达到了 maxiter
并且已经达到了比开始时更小的函数值,但它只是没有停止。由于它在 jupyter 中运行,因此在单元完成之前我无法到达 res
。
最佳答案
根据docs回调应该是一个可调用的,返回 True
来终止,并具有以下格式 callback(xk)
。而在您的代码中,您将其定义为类的初始化。相反,您应该定义类的实例,然后将其 __call__()
函数分配给 callback
,如下所示:
import time
import warnings
import numpy as np
from scipy.optimize import minimize, rosen
class TookTooLong(Warning):
pass
class MinimizeStopper(object):
def __init__(self, max_sec=10):
self.max_sec = max_sec
self.start = time.time()
def __call__(self, xk):
# callback to terminate if max_sec exceeded
elapsed = time.time() - self.start
if elapsed > self.max_sec:
warnings.warn("Terminating optimization: time limit reached",
TookTooLong)
else:
# you might want to report other stuff here
print("Elapsed: %.3f sec" % elapsed)
# init stopper
minimize_stopper = MinimizeStopper()
# minimze
res = minimize(rosen,
x0 = np.random.randint(5, size=128),
method ="BFGS",
tol = 0.01,
options = {"maxiter":10, "disp":True},
callback = minimize_stopper.__call__)
或者,您可以为最小化器定义一个类,并在其中构建一个回调函数以在一定时间后终止最小化。这可以这样完成:
import time
import warnings
import numpy as np
from scipy.optimize import minimize, rosen
class TookTooLong(Warning):
pass
class Minimizer:
def __init__(self, timeout, maxiter):
self.timeout = timeout
self.maxiter = maxiter
def minimize(self):
self.start_time = time.time()
# minimize
res = minimize(rosen,
x0 = np.random.randint(5, size=128),
method ="BFGS",
tol = 0.01,
options = {"maxiter":self.maxiter, "disp":True},
callback = self.callback)
return res
def callback(self, x):
# callback to terminate if max_sec exceeded
elapsed = time.time() - self.start_time
if elapsed > self.timeout:
warnings.warn("Terminating optimization: time limit reached",
TookTooLong)
return True
else:
print("Elapsed: %.3f sec" % elapsed)
# init minimizer and minimize
minimizer = Minimizer(0.1, 100)
result = minimizer.minimize()
使用以下命令测试这些代码:timeout=0.1 & maxiter=100
,然后 timeout=10 & maxiter=10
以观察两种类型的终止。
关于python - scipy.optimize.minimize 不会在 maxiter 或回调处停止,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/56252003/