CobylaOptimizer¶

class CobylaOptimizer(rhobeg=1.0, rhoend=0.0001, maxfun=1000, disp=None, catol=0.0002, trials=1, clip=100.0)[source]¶

Bases: qiskit.optimization.algorithms.multistart_optimizer.MultiStartOptimizer

The SciPy COBYLA optimizer wrapped as an Qiskit OptimizationAlgorithm.

This class provides a wrapper for scipy.optimize.fmin_cobyla (https://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.optimize.fmin_cobyla.html) to be used within the optimization module. The arguments for fmin_cobyla are passed via the constructor.

Examples

>>> from qiskit.optimization.problems import QuadraticProgram
>>> from qiskit.optimization.algorithms import CobylaOptimizer
>>> problem = QuadraticProgram()
>>> # specify problem here
>>> optimizer = CobylaOptimizer()
>>> result = optimizer.solve(problem)

Initializes the CobylaOptimizer.

This initializer takes the algorithmic parameters of COBYLA and stores them for later use of fmin_cobyla when solve() is invoked. This optimizer can be applied to find a (local) optimum for problems consisting of only continuous variables.

Parameters

rhobeg (float) – Reasonable initial changes to the variables.
rhoend (float) – Final accuracy in the optimization (not precisely guaranteed). This is a lower bound on the size of the trust region.
disp (Optional[int]) – Controls the frequency of output; 0 implies no output. Feasible values are {0, 1, 2, 3}.
maxfun (int) – Maximum number of function evaluations.
catol (float) – Absolute tolerance for constraint violations.
trials (int) – The number of trials for multi-start method. The first trial is solved with the initial guess of zero. If more than one trial is specified then initial guesses are uniformly drawn from [lowerbound, upperbound] with potential clipping.
clip (float) – Clipping parameter for the initial guesses in the multi-start method. If a variable is unbounded then the lower bound and/or upper bound are replaced with the -clip or clip values correspondingly for the initial guesses.

Methods

`get_compatibility_msg`	Checks whether a given problem can be solved with this optimizer.
`is_compatible`	Checks whether a given problem can be solved with the optimizer implementing this method.
`multi_start_solve`	Applies a multi start method given a local optimizer.
`solve`	Tries to solves the given problem using the optimizer.

Attributes

clip¶

Returns the clip value for this optimizer.

Return type: float
Returns: The clip value.

trials¶

Returns the number of trials for this optimizer.

Return type: int
Returns: The number of trials.