axiter : int, optional
The maximum number of generations over which the entire population is
evolved. The maximum number of function evaluations (with no polishing)
is: ``(maxiter + 1) * popsize * (N - N_equal)``
popsize : int, optional
A multiplier for setting the total population size. The population has
``popsize * (N - N_equal)`` individuals. This keyword is overridden if
an initial population is supplied via the `init` keyword. When using
``init='sobol'`` the population size is calculated as the next power
of 2 after ``popsize * (N - N_equal)``.
tol : float, optional
Relative tolerance for convergence, the solving stops when
``np.std(population_energies) <= atol + tol * np.abs(np.mean(population_energies))``,
where and `atol` and `tol` are the absolute and relative tolerance
respectively.
mutation : float or tuple(float, float), optional
The mutation constant. In the literature this is also known as
differential weight, being denoted by F.
If specified as a float it should be in the range [0, 2].
If specified as a tuple ``(min, max)`` dithering is employed. Dithering
randomly changes the mutation constant on a generation by generation
basis. The mutation constant for that generation is taken from
U[min, max). Dithering can help speed convergence significantly.
Increasing the mutation constant increases the search radius, but will
slow down convergence.
recombination : float, optional
The recombination constant, should be in the range [0, 1]. In the
literature this is also known as the crossover probability, being
denoted by CR. Increasing this value allows a larger number of mutants
to progress into the next generation, but at the risk of population
stability.
rng : {None, int, `numpy.random.Generator`}, optional
..versionchanged:: 1.15.0
As part of the `SPEC-007 `_
transition from use of `numpy.random.RandomState` to
`numpy.random.Generator` this keyword was changed from `seed` to `rng`.
For an interim period both keywords will continue to work (only specify
one of them). After the interim period using the `seed` keyword will emit
warnings. The behavior of the `seed` and `rng` keywords is outlined below.
If `rng` is passed by keyword, types other than `numpy.random.Generator` are
passed to `numpy.random.default_rng` to instantiate a `Generator`.
If `rng` is already a `Generator` instance, then the provided instance is
used.
If this argument is passed by position or `seed` is passed by keyword, the
behavior is:
- If `seed` is None (or `np.random`), the `numpy.random.RandomState`
singleton is used.
- If `seed` is an int, a new `RandomState` instance is used,
seeded with `seed`.
- If `seed` is already a `Generator` or `RandomState` instance then
that instance is used.
Specify `seed`/`rng` for repeatable minimizations.
disp : bool, optional
Prints the evaluated `func` at every iteration.
callback : callable, optional
A callable called after each iteration. Has the signature:
``callback(intermediate_result: OptimizeResult)``
where ``intermediate_result`` is a keyword parameter containing an
`OptimizeResult` with attributes ``x`` and ``fun``, the best solution
found so far and the objective function. Note that the name
of the parameter must be ``intermediate_result`` for the callback
to be passed an `OptimizeResult`.
The callback also supports a signature like:
``callback(x, convergence: float=val)``
``val`` represents the fractional value of the population convergence.
When ``val`` is greater than ``1.0``, the function halts.
Introspection is used to determine which of the signatures is invoked.
Global minimization will halt if the callback raises ``StopIteration``
or returns ``True``; any polishing is still carried out.
.. versionchanged:: 1.12.0
callback accepts the ``intermediate_result`` keyword.
polish : bool, optional
If True (default), then `scipy.optimize.minimize` with the `L-BFGS-B`
method is used to polish the best population member at the end, which
can improve the minimization slightly. If a constrained problem is
being studied then the `trust-constr` method is used instead. For large
problems with many constraints, polishing can take a long time due to
the Jacobian computations.
maxfun : int, optional
Set the maximum number of function evaluations. However, it probably
makes more sense to set `maxiter` instead.
init : str or array-like, optional
Specify which type of population initialization is performed. Should be
one of:
- 'latinhypercube'
- 'sobol'
- 'halton'
- 'random'
- array specifying the initial population. The array should have
shape ``(S, N)``, where S is the total population size and
N is the number of parameters.
`init` is clipped to `bounds` before use.
The default is 'latinhypercube'. Latin Hypercube sampling tries to
maximize coverage of the available parameter space.
'sobol' and 'halton' are superior alternatives and maximize even more
the parameter space. 'sobol' will enforce an initial population
size which is calculated as the next power of 2 after
``popsize * (N - N_equal)``. 'halton' has no requirements but is a bit
less efficient. See `scipy.stats.qmc` for more details.
'random' initializes the population randomly - this has the drawback
that clustering can occur, preventing the whole of parameter space
being covered. Use of an array to specify a population could be used,
for example, to create a tight bunch of initial guesses in an location
where the solution is known to exist, thereby reducing time for
convergence.
atol : float, optional
Absolute tolerance for convergence, the solving stops when
``np.std(pop) <= atol + tol * np.abs(np.mean(population_energies))``,
where and `atol` and `tol` are the absolute and relative tolerance
respectively.
updating : {'immediate', 'deferred'}, optional
If ``'immediate'``, the best solution vector is continuously updated
within a single generation [4]_. This can lead to faster convergence as
trial vectors can take advantage of continuous improvements in the best
solution.
With ``'deferred'``, the best solution vector is updated once per
generation. Only ``'deferred'`` is compatible with parallelization or
vectorization, and the `workers` and `vectorized` keywords can
over-ride this option.
workers : int or map-like callable, optional
If `workers` is an int the population is subdivided into `workers`
sections and evaluated in parallel
(uses `multiprocessing.Pool `).
Supply `-1` to use all cores available to the Process.
Alternatively supply a map-like callable, such as
`multiprocessing.Pool.map` for evaluating the population in parallel.
This evaluation is carried out as ``workers(func, iterable)``.
This option will override the `updating` keyword to
`updating='deferred'` if `workers != 1`.
Requires that `func` be pickleable.
constraints : {NonLinearConstraint, LinearConstraint, Bounds}
Constraints on the solver, over and above those applied by the `bounds`
kwd. Uses the approach by Lampinen.
x0 : None or array-like, optional
Provides an initial guess to the minimization. Once the population has
been initialized this vector replaces the first (best) member. This
replacement is done even if `init` is given an initial population.
``x0.shape == (N,)``.
integrality : 1-D array, optional
For each decision variable, a boolean value indicating whether the
decision variable is constrained to integer values. The array is
broadcast to ``(N,)``.
If any decision variables are constrained to be integral, they will not
be changed during polishing.
Only integer values lying between the lower and upper bounds are used.
If there are no integer values lying between the bounds then a
`ValueError` is raised.
vectorized : bool, optional
If ``vectorized is True``, `func` is sent an `x` array with
``x.shape == (N, S)``, and is expected to return an array of shape
``(S,)``, where `S` is the number of solution vectors to be calculated.
If constraints are applied, each of the functions used to construct
a `Constraint` object should accept an `x` array with
``x.shape == (N, S)``, and return an array of shape ``(M, S)``, where
`M` is the number of constraint components.
This option is an alternative to the parallelization offered by
`workers`, and may help in optimization speed. This keyword is
ignored if ``workers != 1``.
This option will override the `updating` keyword to
``updating='deferred'``.
Ú