IndexError: too many indices for array in Scipy.Optimize - python-3.x

Question

I'm trying to debbug some code with Scipy.Optimize.
The bug comes from the constante: the optimisation works fine without it. The constante itself seems to works fine outside scipy.optimize (the variable testconst is computed normally). The code is the following:
from scipy.optimize import minimize
import numpy as np
def totaldist(dy):
n = np.shape(dy)[0]
temp = 0
for i in range(n):
temp += dy[i] ** 2
return -0.5 * temp
def create_bond(dy_max):
n = np.shape(dy_max)[0]
bond = np.zeros((n, 2))
for i in range(n):
bond[i, :] = [0, dy_max[i]]
tot = tuple([tuple(row) for row in bond])
return tot
# def create_const(type_x, dx, gamma, P):
def create_const(dy, *args):
arg = np.asarray(args)
n = np.shape(dy)[0]
dx = np.zeros((n, 2))
bnd = np.zeros((n, 2))
# from args to numpy array
type_x = np.zeros(n)
dP = 0
delta1 = np.zeros(n)
delta2 = np.zeros(n)
gamma = np.zeros((n, n))
for i in range(n):
a, b = bndr(arg[0, i])
delta1[i] = arg[0, i + n + 1]
delta2[i] = arg[0, i + 2*n + 1]
dx[i, 0] = (b - a) * dy[i]
gamma = GammaApprox(delta1, delta2, dx[:, 1], dx[:, 0])
d = np.dot(delta2, dx[:, 0])
g = np.dot(dx[:, 0], gamma)
g = np.dot(g, dx[:, 0])
dP = float(arg[0, n])
return d + 0.5 * g - dP
def GammaApprox(delta1, delta2, x1, x2):
n = np.shape(delta1)[0]
gamma = np.zeros((n, n))
for i in range(n):
if x2[i] == x1[i]:
gamma[i, i] = 0
else:
gamma[i, i] = (delta2[i] - delta1[i]) / (x2[i] - x1[i])
return gamma
def GetNewPoint(x1, x2, delta1, delta2, type_x, P):
n = np.shape(delta1)[0]
dmax = np.zeros(n)
dy0 = np.zeros(n)
# create the inequality data and initial points
for i in range(n):
a, b = bndr(type_x[i])
if x2[i] > x1[i]:
dmax[i] = (x2[i] - x1[i])/(b - a)
dy0[i] = 1 / (b - a) * (x2[i] - x1[i]) / 2
else:
dmax[i] = (x1[i] - x2[i])/(b - a)
dy0[i] = 1 / (b - a) * (x1[i] - x2[i]) / 2
bond = create_bond(dmax)
# create the args tuple
arg = ()
# type x
for i in range(n):
arg = arg + (type_x[i],)
# dP
arg = arg + (abs(P[0] - P[1]), )
# delta1
for i in range(n):
arg = arg + (delta1[i], )
# delta1
for i in range(n):
arg = arg + (delta2[i], )
testconst = create_const(dy0, arg)
# create the equality constraint
con1 = {'type': 'eq', 'fun': create_const}
cons = ([con1, ])
solution = minimize(totaldist, dy0, args=arg, method='SLSQP', bounds=bond, constraints=cons, options={'disp': True})
x = solution.x
print(x)
return x
def bndr(type_x):
if type_x == 'normal':
x_0 = -5
x_f = 1.5
if type_x == 'lognorm':
x_0 = 0.0001
x_f = 5
if type_x == 'chisquare':
x_0 = 0.0001
x_f = (0.8 * (10 ** .5))
return x_0, x_f
def test():
x1 = np.array([0.0001, 0.0001, -5])
x2 = np.array([1.6673, 0.84334, -5])
delta1 = np.array([0, 0, 0])
delta2 = np.array([2.44E-7, 2.41E-6, 4.07E-7])
type_x = np.array(['lognorm', 'chisquare', 'normal'])
P = (0, 6.54E-8)
f = GetNewPoint(x1, x2, delta1, delta2, type_x, P)
return f
test()
the error message is the following:
Traceback (most recent call last):
File "D:/Anaconda Project/TestQP - Simplified/QP.py", line 134, in <module>
test()
File "D:/Anaconda Project/TestQP - Simplified/QP.py", line 130, in test
f = GetNewPoint(x1, x2, delta1, delta2, type_x, P)
File "D:/Anaconda Project/TestQP - Simplified/QP.py", line 103, in GetNewPoint
solution = minimize(totaldist, dy0, args=arg, method='SLSQP', bounds=bond, constraints=cons, options={'disp': True})
File "C:\Program Files\Anaconda\lib\site-packages\scipy\optimize\_minimize.py", line 458, in minimize
constraints, callback=callback, **options)
File "C:\Program Files\Anaconda\lib\site-packages\scipy\optimize\slsqp.py", line 311, in _minimize_slsqp
meq = sum(map(len, [atleast_1d(c['fun'](x, *c['args'])) for c in cons['eq']]))
File "C:\Program Files\Anaconda\lib\site-packages\scipy\optimize\slsqp.py", line 311, in <listcomp>
meq = sum(map(len, [atleast_1d(c['fun'](x, *c['args'])) for c in cons['eq']]))
File "D:/Anaconda Project/TestQP - Simplified/QP.py", line 40, in create_const
a, b = bndr(arg[0, i])
IndexError: too many indices for array
I find roughly similar error in the website like: IndexError: index 1 is out of bounds for axis 0 with size 1/ForwardEuler
...but I failed to see it's really the same problem.

Answer 1

args is not passed to constraint-functions (automatically)!
This is indicated in the docs:
args : tuple, optional
Extra arguments passed to the objective function and its derivatives (Jacobian, Hessian).
You can see the problem easily by adding a print:
def create_const(dy, *args):
print('args:')
print(args)
arg = np.asarray(args)
...
which will output something like:
args:
(('lognorm', 'chisquare', 'normal', 6.54e-08, 0, 0, 0, 2.4400000000000001e-07, 2.4099999999999998e-06, 4.0699999999999998e-07),)
args:
()
ERROR...
If you remove your test (which is manually passing args; which works) testconst = create_const(dy0, arg), you will see only the non-working output:
args:
()
ERROR...
Constraints have their own mechanism of passing args as described in the docs:
constraints : dict or sequence of dict, optional
Constraints definition (only for COBYLA and SLSQP). Each constraint is defined in a dictionary with fields:
type : str
Constraint type: ‘eq’ for equality, ‘ineq’ for inequality.
fun : callable
The function defining the constraint.
jac : callable, optional
The Jacobian of fun (only for SLSQP).
args : sequence, optional
Extra arguments to be passed to the function and Jacobian.
Equality constraint means that the constraint function result is to be zero whereas inequality means that it is to be non-negative. Note that COBYLA only supports inequality constraints.
In your case:
con1 = {'type': 'eq', 'fun': create_const} # incomplete!
con1 = {'type': 'eq', 'fun': create_const, 'args': (arg,)} # (,)
# to make it behave as needed
# for your code!
This will make it run until some other problem occurs!