Scipy minimize error: 'numpy.float64' object is not callable

Question

I have defined a Class to minimize a standard function called rosen, in order to minimize rosen, the scipy.minimize function needs to call rosen repeatedly to minimize it.

from scipy.optimize import minimize
import numpy as np


class LocalMultivariateOptimization:

    def __init__(self, initial_guess_parameters, xtol, method):
        self.xtol = xtol
        self.method = method
        self.x = initial_guess_parameters

    def minimize(self):
        res = minimize(self.rosen(self.x), self.x, method=self.method, options={'xtol': self.xtol, 'disp': True})

    def rosen(self, x):
        return sum(100.0 * (x[1:] - x[:-1] ** 2.0) ** 2.0 + (1 - x[:-1]) ** 2.0)


args0 = np.array([1.3, 0.7, 0.8, 1.9, 1.2])
xtol = 1e-8
method = 'nelder-mead'

LocalMultivariateOptimizationObject = LocalMultivariateOptimization(args0, xtol, method)
LocalMultivariateOptimizationObject.minimize()

results in

TypeError: 'numpy.float64' object is not callable

This is my first learning attempt at OOP in Python. What am I doing wrong here? I am calling the function instead of sending just the data in minimize(). Which is basically correct.

I think in res = minimize(self.rosen(self.x),... you want res = minimize(self.rosen,... — progmatico
– progmatico, Commented Jan 26, 2019 at 17:18

Stephen Rauch · Accepted Answer · 2019-01-26 17:29:17Z

3

The first parameter to:

scipy.optimize.minimize()

is a callable. This bascially means you need to pass a function or a method that can be called by the optimization code. You however passed:

self.rosen(self.x)

which has already been called, instead you need:

self.rosen

In addition your minimize() method is not returning anything and should look more like:

def minimize(self):
    return minimize(self.rosen, self.x, method=self.method,
                    options={'xtol': self.xtol, 'disp': True})

edited Jan 26, 2019 at 17:29

answered Jan 26, 2019 at 17:20

Stephen Rauch♦

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3 Comments

Rene Duchamp Over a year ago

Thank you for explaining about the callable parameter. However, after changing to the minimize(self) function you gave, it resulted in TypeError: rosen() takes 1 positional argument but 2 were given

Stephen Rauch Over a year ago

So I just took your posted code and put in my minimize() and there was no exception thrown.

Rene Duchamp Over a year ago

I am very sorry, I was experimenting, and had some other variations compared to the original code I posted here. Your answer is correct.

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