qiskit.optimization.algorithms.CobylaOptimizer

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

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.

サンプル

>>> 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.

パラメータ

• 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.

__init__(rhobeg=1.0, rhoend=0.0001, maxfun=1000, disp=None, catol=0.0002, trials=1, clip=100.0)

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.

パラメータ

• 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

__init__([rhobeg, rhoend, maxfun, disp, …])	Initializes the CobylaOptimizer.
get_compatibility_msg(problem)	Checks whether a given problem can be solved with this optimizer.
is_compatible(problem)	Checks whether a given problem can be solved with the optimizer implementing this method.
multi_start_solve(minimize, problem)	Applies a multi start method given a local optimizer.
solve(problem)	Tries to solves the given problem using the optimizer.

Attributes

clip	Returns the clip value for this optimizer.
trials	Returns the number of trials for this optimizer.

property clip

Returns the clip value for this optimizer.

戻り値の型

float

戻り値

The clip value.

get_compatibility_msg(problem)

Checks whether a given problem can be solved with this optimizer.

Checks whether the given problem is compatible, i.e., whether the problem contains only continuous variables, and otherwise, returns a message explaining the incompatibility.

パラメータ

problem (QuadraticProgram) – The optimization problem to check compatibility.

戻り値の型

str

戻り値

Returns a string describing the incompatibility.

is_compatible(problem)

Checks whether a given problem can be solved with the optimizer implementing this method.

パラメータ

problem (QuadraticProgram) – The optimization problem to check compatibility.

戻り値の型

bool

戻り値

Returns True if the problem is compatible, False otherwise.

multi_start_solve(minimize, problem)

Applies a multi start method given a local optimizer.

パラメータ

• minimize (Callable[[array], Tuple[array, Any]]) – A callable object that minimizes the problem specified

• problem (QuadraticProgram) – A problem to solve

戻り値の型

OptimizationResult

戻り値

The result of the multi start algorithm applied to the problem.

solve(problem)

Tries to solves the given problem using the optimizer.

Runs the optimizer to try to solve the optimization problem.

パラメータ

problem (QuadraticProgram) – The problem to be solved.

戻り値の型

OptimizationResult

戻り値

The result of the optimizer applied to the problem.

例外

QiskitOptimizationError – If the problem is incompatible with the optimizer.

property trials

Returns the number of trials for this optimizer.

戻り値の型

int

戻り値

The number of trials.