I want to solve the following optimization problem with scipy (python3):
where I[.,.] is the "incomplete gamma function" (scipy.special.gammainc)
I followed the scipy optimization guide and came up with this code:
from scipy.special import gammainc
from scipy.optimize import NonlinearConstraint
from scipy.optimize import BFGS
from scipy.optimize import minimize
import numpy as np
q = 200
k = 1.5625
alpha = 0.03125
def func(s):
return s
def constraints(s):
return q - k/alpha * (gammainc(k+1, s*alpha) + gammainc(k+1, (s+q)*alpha)) + s*gammainc(k, s*alpha) + (s+q)*gammainc(k, (s+q)*alpha)
nonlinear_constraint = NonlinearConstraint(constraints, -np.inf, 10.0, jac='2-point', hess=BFGS())
s0 = 1000
res = minimize(func, s0, method='trust-constr', jac='2-point', hess=BFGS(), constraints=[nonlinear_constraint], options={'verbose': 1})
print(res.x)
when I run the code, I get this (error) output:
/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/optimize/_hessian_update_strategy.py:187: UserWarning: delta_grad == 0.0. Check if the approximated function is linear. If the function is linear better results can be obtained by defining the Hessian as zero instead of using quasi-Newton approximations.
'approximations.', UserWarning)
Traceback (most recent call last):
File "s_opt.py", line 23, in <module>
res = minimize(func, s0, method='trust-constr', jac='2-point', hess=BFGS(), constraints=[nonlinear_constraint], options={'verbose': 1})
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/optimize/_minimize.py", line 622, in minimize
callback=callback, **options)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/optimize/_trustregion_constr/minimize_trustregion_constr.py", line 519, in _minimize_trustregion_constr
factorization_method)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/optimize/_trustregion_constr/tr_interior_point.py", line 329, in tr_interior_point
factorization_method, trust_lb, trust_ub, subprob.scaling)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/optimize/_trustregion_constr/equality_constrained_sqp.py", line 121, in equality_constrained_sqp
lb_t, ub_t)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/optimize/_trustregion_constr/qp_subproblem.py", line 499, in projected_cg
r = Z.dot(H.dot(x) + c)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/sparse/linalg/interface.py", line 415, in dot
return self.matvec(x)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/sparse/linalg/interface.py", line 229, in matvec
y = self._matvec(x)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/sparse/linalg/interface.py", line 527, in _matvec
return self.__matvec_impl(x)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/optimize/_trustregion_constr/projections.py", line 193, in null_space
aux2 = scipy.linalg.solve_triangular(R, aux1, lower=False)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/linalg/basic.py", line 336, in solve_triangular
b1 = _asarray_validated(b, check_finite=check_finite)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/scipy/_lib/_util.py", line 246, in _asarray_validated
a = toarray(a)
File "/home/andreasziegler/miniconda3/lib/python3.7/site-packages/numpy/lib/function_base.py", line 499, in asarray_chkfinite
"array must not contain infs or NaNs")
ValueError: array must not contain infs or NaNs
which tells me that I did something wrong. It's the first time I use the optimizer in scipy and therefore chances are high, that I misunderstand something (essential). I'm glad for any hint.
