def logp(self, pvals=None):
"""
Calculate the log-prior of the system
Parameters
----------
pvals : array-like or refnx.analysis.Parameters
values for the varying or entire set of parameters
Returns
-------
logp : float
log-prior probability
Notes
-----
The log-prior is calculated as:
.. code-block:: python
logp = np.sum(param.logp() for param in
self.varying_parameters())
"""
self.setp(pvals)
logp = np.sum([
param.logp() for param in f_unique(
p for p in flatten(self.parameters) if p.vary)
])
if not np.isfinite(logp):
return -np.inf
return logp
def setp(self, pvals):
"""
Set the parameters from pvals.
Parameters
----------
pvals : array-like or refnx.analysis.Parameters
values for the varying or entire set of parameters
"""
if pvals is None:
return
# set here rather than delegating to a Parameters
# object, because it may not necessarily be a
# Parameters object
_varying_parameters = self.varying_parameters()
if len(pvals) == len(_varying_parameters):
for idx, param in enumerate(_varying_parameters):
param.value = pvals[idx]
return
# values supplied are enough to specify all parameter values
# even those that are repeated
flattened_parameters = list(flatten(self.parameters))
if len(pvals) == len(flattened_parameters):
for idx, param in enumerate(flattened_parameters):
param.value = pvals[idx]
return
raise ValueError('Incorrect number of values supplied, supply either'
' the full number of parameters, or only the varying'
' parameters.')
def test_spline_smoke(self):
# smoke test to make Spline at least gives us something
a = Spline(100, [2], [0.5], zgrad=False, microslab_max_thickness=1)
s = self.left | a | self.right | self.solvent
b = a.slabs(s)
assert_equal(b[:, 2], 0)
# microslabs are assessed in the middle of the slab
assert_equal(b[0, 1], a(0.5 * b[0, 0], s))
# with the ends turned off the profile should be a straight line
assert_equal(a(50, s), 2.0)
# construct a structure
a = Spline(
100,
[2.0, 3.0, 4.0],
[0.25] * 3,
zgrad=False,
microslab_max_thickness=1,
)
# s.solvent = None
s = self.left | a | self.right | self.solvent
# calculate an SLD profile
s.sld_profile()
# ask for the parameters
for p in flatten(s.parameters):
assert_(isinstance(p, Parameter))
# s.solvent is not None
s.solvent = self.solvent
# calculate an SLD profile
s.sld_profile()
def _calculate_constraints(i, objective):
# builds constraints strings for an objective which has a local variable
# name of objective_{i}
all_pars = list(flatten(objective.parameters))
var_pars = objective.varying_parameters()
non_var_pars = [p for p in all_pars if p not in var_pars]
# now get parameters with constraints
con_pars = [par for par in non_var_pars if par.constraint is not None]
tab = " "
constrain_strings = [
tab + "parameters = list(flatten("
"objective_{}.parameters))".format(i)
]
for con_par in con_pars:
idx = all_pars.index(con_par)
con_tree = constraint_tree(con_par.constraint)
for j, v in enumerate(con_tree):
if v in operators:
con_tree[j] = operators[v]
elif v in all_pars:
con_tree[j] = "parameters[{}]".format(all_pars.index(v))
else:
con_tree[j] = repr(v)
s = ", ".join(con_tree)
constraint = "build_constraint_from_tree([" + s + "])"
item = tab + "parameters[{}].constraint = {}".format(idx, constraint)
constrain_strings.append(item)
return constrain_strings
def _interfaces_get(self):
repeats = round(abs(self.repeats.value))
interfaces = list(flatten([i.interfaces for i in self.data]))
if repeats > 1:
interfaces = interfaces * repeats
return interfaces
def test_structure_construction(self):
# structures are constructed by or-ing slabs
# test that the slab representation is correct
assert_equal(
self.s.slabs(),
np.array([[0, 0, 0, 0, 0], [100, 3.47, 0, 5, 0],
[0, 6.36, 0, 4, 0]]))
self.s[1] = SLD(3.47 + 1j, name='sio2')(100, 5)
self.s[1].vfsolv.value = 0.9
oldpars = len(list(flatten(self.s.parameters)))
# slabs have solvent penetration
self.s.solvent = SLD(5 + 1.2j)
sld = 5 * 0.9 + 0.1 * 3.47
sldi = 1 * 0.1 + 0.9 * 1.2
assert_almost_equal(
self.s.slabs(),
np.array([[0, 0, 0, 0, 0], [100, sld, sldi, 5, 0.9],
[0, 6.36, 0, 4, 0]]))
# when the structure._solvent is not None, but an SLD object, then
# it's number of parameters should increase by 2.
newpars = len(list(flatten(self.s.parameters)))
assert_equal(newpars, oldpars + 2)
# by default solvation is done by backing medium
self.s.solvent = None
sld = 6.36 * 0.9 + 0.1 * 3.47
sldi = 1 * 0.1
assert_almost_equal(
self.s.slabs(),
np.array([[0, 0, 0, 0, 0], [100, sld, sldi, 5, 0.9],
[0, 6.36, 0, 4, 0]]))
# by default solvation is done by backing medium, except when structure
# is reversed
self.s.reverse_structure = True
sld = 0 * 0.9 + 0.1 * 3.47
sldi = 0 * 0.9 + 1 * 0.1
assert_almost_equal(
self.s.slabs(),
np.array([[0, 6.36, 0, 0, 0], [100, sld, sldi, 4, 0.9],
[0, 0, 0, 5, 0]]))
def __repr__(self):
s = list()
s.append("{:_>80}".format(''))
s.append("Parameters: {0: ^15}".format(repr(self.name)))
for el in self._pprint():
s.append(el)
return '\n'.join(list(flatten(s)))
def names(self):
"""
Returns
-------
names : list
A list of all the names of all the :class:`Parameter` contained in
this object.
"""
return [param.name for param in flatten(self.data)]
def pvals(self, pvals):
varying = [param for param in f_unique(flatten(self.data))
if param.vary]
if np.size(pvals) == len(varying):
[setattr(param, 'value', pvals[i]) for i, param
in enumerate(varying)]
return
flattened_parameters = list(flatten(self.data))
if np.size(pvals) == len(flattened_parameters):
[setattr(param, 'value', pvals[i]) for i, param
in enumerate(flattened_parameters)]
return
else:
raise ValueError("You supplied the wrong number of values %d when "
"setting this Parameters.pvals attribute"
% len(pvals))
def constrained_parameters(self):
"""
Returns
-------
constrained_parameters : list
A list of unique :class:`Parameter` contained in this object that
have constraints.
"""
return [param for param in f_unique(flatten(self.data))
if param.constraint is not None]
def nvary(self):
"""
Returns
-------
nvary : int
The number of :class:`Parameter` contained in this object that are
allowed to vary.
"""
return len([1 for param in f_unique(flatten(self.data)) if param.vary])
def constraint_tree(expr):
"""
builds a mathematical tree of a constraint expression
this can be fed into build_constraint_from_tree to
reconstitute a constraint
"""
if isinstance(expr, Parameter):
return [expr]
if isinstance(expr, Constant):
return [expr]
return list(flatten(_constraint_tree_helper(expr)))
def dependencies(self):
dep_list = []
for _dep in self._deps:
if isinstance(_dep, Parameter):
if _dep.constraint is not None:
dep_list.append(_dep.dependencies())
else:
dep_list.append(_dep)
if isinstance(_dep, (_UnaryOp, _BinaryOp)):
dep_list.append(_dep.dependencies())
return list(flatten(dep_list))
def flattened(self, unique=False):
"""
A list of all the :class:`Parameter` contained in this object,
including those contained within :class:`Parameters` at any depth.
Parameters
----------
unique : bool
The list will only contain unique objects.
Returns
-------
params : list
A list of :class:`Parameter` contained in this object.
"""
if unique:
return list(f_unique(flatten(self.data)))
else:
return list(flatten(self.data))
def logp(self):
"""
Calculates logp for all the parameters
Returns
-------
logp : float
Log probability for all the parameters
"""
# logp for all the parameters
return np.sum([param.logp() for param in f_unique(flatten(self.data))
if param.vary])
def _on_slab_varies_modified(self, change):
d = self.param_widgets_link
slab = self.slab
for par in flatten(slab.parameters):
if id(par) in d and change["owner"] in d[id(par)]:
wids = d[id(par)]
par.vary = wids[1].value
break
self.param_being_varied = change["owner"]
self.view_changed = time.time()
def plot_corner(objective, samples):
labels = []
for i in flatten(objective.parameters.varying_parameters()):
labels.append(i.name)
fig = corner.corner(samples,
labels=labels,
quantiles=[0.025, 0.5, 0.975],
show_titles=True,
title_kwargs={"fontsize": 12})
return fig
def refresh(self):
"""
Updates the widget values from the underlying `Slab` parameters.
"""
d = self.param_widgets_link
ids = {id(p): p for p in flatten(self.slab.parameters) if id(p) in d}
for idx, par in ids.items():
widgets = d[idx]
widgets[0].value = par.value
widgets[1].value = par.vary
widgets[2].value = par.bounds.lb
widgets[3].value = par.bounds.ub
def varying_parameters(self):
"""
Unique list of varying parameters
Returns
-------
p : list
Unique list of varying parameters
"""
p = [param for param in f_unique(flatten(self.data)) if param.vary]
q = Parameters()
q.data = p
return q
def varying_parameters(self):
"""
Returns
-------
varying_parameters : refnx.analysis.Parameters
The varying Parameter objects allowed to vary during the fit.
"""
# create and return a Parameters object because it has the
# __array__ method, which allows one to quickly get numerical values.
p = Parameters()
p.data = list(f_unique(p for p in flatten(self.parameters) if p.vary))
return p
def _on_slab_limits_modified(self, change):
slab = self.slab
d = self.param_widgets_link
for par in flatten(slab.parameters):
if id(par) in d and change["owner"] in d[id(par)]:
wids = d[id(par)]
loc = wids.index(change["owner"])
if loc == 2:
par.bounds.lb = wids[loc].value
break
elif loc == 3:
par.bounds.ub = wids[loc].value
break
else:
return
def _on_slab_params_modified(self, change):
d = self.param_widgets_link
slab = self.slab
for par in flatten(slab.parameters):
if id(par) in d and change['owner'] in d[id(par)]:
wids = d[id(par)]
loc = wids.index(change['owner'])
if loc == 0:
par.value = wids[0].value
break
elif loc == 1:
par.vary = wids[1].value
break
self.param_being_varied = change['owner']
self.view_changed = time.time()
def __init__(self, data, model, parent=QtCore.QModelIndex(), flat=True):
"""
Parameters
----------
flat : bool
If `flat is True`, then this superclass will flatten out all
the parameters in a model and append them as child items.
"""
super(ComponentNode, self).__init__(data, model, parent)
if flat:
for par in flatten(data.parameters):
pn = ParNode(par, model, parent=self)
self.appendChild(pn)
else:
for p in data.parameters:
if isinstance(p, Parameters):
n = ParametersNode(p, model, self)
if isinstance(p, Parameter):
n = ParNode(p, model, self)
self.appendChild(n)
def test_materialsld(self):
p = MaterialSLD("SiO2", density=2.2, name="silica")
sldc = complex(p)
assert_allclose(sldc.real, 3.4752690258246504)
assert_allclose(sldc.imag, 1.0508799522721932e-05)
assert p.probe == "neutron"
# is X-ray SLD correct?
p.wavelength = 1.54
p.probe = "x-ray"
sldc = complex(p)
assert_allclose(sldc.real, 18.864796064009866)
assert_allclose(sldc.imag, 0.2436013463223236)
assert len(p.parameters) == 1
assert p.formula == "SiO2"
# the density value should change the SLD
p.probe = "neutron"
p.density.value = 4.4
sldc = complex(p)
assert_allclose(sldc.real, 3.4752690258246504 * 2)
assert_allclose(sldc.imag, 1.0508799522721932e-05 * 2)
# should be able to make a Slab from MaterialSLD
slab = p(10, 3)
assert isinstance(slab, Slab)
slab = Slab(10, p, 3)
assert isinstance(slab, Slab)
# make a full structure and check that the reflectivity calc works
air = SLD(0)
sio2 = MaterialSLD("SiO2", density=2.2)
si = MaterialSLD("Si", density=2.33)
s = air | sio2(10, 3) | si(0, 3)
s.reflectivity(np.linspace(0.005, 0.3, 100))
p = s.parameters
assert len(list(flatten(p))) == 5 + 4 + 4
def _micro_slabs(self, slice_size=0.5):
"""
Creates a microslab representation of the Structure.
Parameters
----------
slice_size : float
Thickness of each slab in the micro-slab representation
Returns
-------
micro_slabs : np.ndarray
The micro-slab representation of the model. See the
`Structure.slabs` method for a description of the array.
"""
# solvate the slabs from each component
sl = [c.slabs(structure=self) for c in self.components]
total_slabs = np.concatenate(sl)
total_slabs[1:-1] = self.overall_sld(total_slabs[1:-1], self.solvent)
total_slabs[:, 0] = np.fabs(total_slabs[:, 0])
total_slabs[:, 3] = np.fabs(total_slabs[:, 3])
# interfaces between all the slabs
_interfaces = self.interfaces
erf_interface = Erf()
i = 0
# the default Interface is None.
# The Component.interfaces property may not have the same length as the
# Component.slabs. Expand it so it matches the number of slabs,
# otherwise the calculation of microslabs fails.
for _interface, _slabs in zip(_interfaces, sl):
if _interface is None or isinstance(_interface, Interface):
f = _interface or erf_interface
_interfaces[i] = [f] * len(_slabs)
i += 1
_interfaces = list(flatten(_interfaces))
_interfaces = [erf_interface if i is None else i for i in _interfaces]
# distance of each interface from the fronting interface
dist = np.cumsum(total_slabs[:-1, 0])
# workout how much space the SLD profile should encompass
zstart = -5. - 8 * total_slabs[1, 3]
zend = 5. + dist[-1] + 8 * total_slabs[-1, 3]
nsteps = int((zend - zstart) / slice_size + 1)
zed = np.linspace(zstart, zend, num=nsteps)
# the output arrays
sld = np.ones_like(zed, dtype=float) * total_slabs[0, 1]
isld = np.ones_like(zed, dtype=float) * total_slabs[0, 2]
# work out the step in SLD at an interface
delta_rho = total_slabs[1:, 1] - total_slabs[:-1, 1]
delta_irho = total_slabs[1:, 2] - total_slabs[:-1, 2]
# the RMS roughness of each step
sigma = total_slabs[1:, 3]
step = Step()
# accumulate the SLD of each step.
for i in range(len(total_slabs) - 1):
f = _interfaces[i + 1]
if sigma[i] == 0:
f = step
p = f(zed, scale=sigma[i], loc=dist[i])
sld += delta_rho[i] * p
isld += delta_irho[i] * p
sld[0] = total_slabs[0, 1]
isld[0] = total_slabs[0, 2]
sld[-1] = total_slabs[-1, 1]
isld[-1] = total_slabs[-1, 2]
micro_slabs = np.zeros((len(zed), 5), float)
micro_slabs[:, 0] = zed[1] - zed[0]
micro_slabs[:, 1] = sld
micro_slabs[:, 2] = isld
return micro_slabs
def slabs(self, **kwds):
r"""
Returns
-------
slabs : :class:`np.ndarray`
Slab representation of this structure.
Has shape (N, 5).
- slab[N, 0]
thickness of layer N
- slab[N, 1]
*overall* SLD.real of layer N (material AND solvent)
- slab[N, 2]
*overall* SLD.imag of layer N (material AND solvent)
- slab[N, 3]
roughness between layer N and N-1
- slab[N, 4]
volume fraction of solvent in layer N.
Notes
-----
If `Structure.reversed is True` then the slab representation order is
reversed. The slab order is reversed before the solvation calculation
is done. I.e. if `Structure.solvent == 'backing'` and
`Structure.reversed is True` then the material that solvates the system
is the component in `Structure[0]`, which corresponds to
`Structure.slab[-1]`.
"""
if not len(self):
return None
if not (isinstance(self.data[-1], Slab)
and isinstance(self.data[0], Slab)):
raise ValueError("The first and last Components in a Structure"
" need to be Slabs")
# Each layer can be given a different type of roughness profile
# that defines transition between successive layers.
# The default interface is specified by None (= Gaussian roughness)
interfaces = flatten(self.interfaces)
if all([i is None for i in interfaces]):
# if all the interfaces are Gaussian, then simply concatenate
# the default slabs property of each component.
sl = [c.slabs(structure=self) for c in self.components]
try:
slabs = np.concatenate(sl)
except ValueError:
# some of slabs may be None. np can't concatenate arr and None
slabs = np.concatenate([s for s in sl if s is not None])
else:
# there is a non-default interfacial roughness, create a microslab
# representation
slabs = self._micro_slabs()
# if the slab representation needs to be reversed.
if self.reverse_structure:
roughnesses = slabs[1:, 3]
slabs = np.flipud(slabs)
slabs[1:, 3] = roughnesses[::-1]
slabs[0, 3] = 0.
if np.any(slabs[:, 4] > 0):
# overall SLD is a weighted average of the vfs and slds
slabs[1:-1] = self.overall_sld(slabs[1:-1], self.solvent)
if self.contract > 0:
return _contract_by_area(slabs, self.contract)
else:
return slabs
def process_chain(objective, chain, nburn=0, nthin=1, flatchain=False):
"""
Process the chain produced by a sampler for a given Objective
Parameters
----------
objective : refnx.analysis.Objective
The Objective function that the Posterior was sampled for
chain : array
The MCMC chain
nburn : int, optional
discard this many steps from the start of the chain
nthin : int, optional
only accept every `nthin` samples from the chain
flatchain : bool, optional
collapse the walkers down into a single dimension.
Returns
-------
[(param, stderr, chain)] : list
List of (param, stderr, chain) tuples.
If `isinstance(objective.parameters, Parameters)` then `param` is a
`Parameter` instance. `param.value`, `param.stderr` and
`param.chain` will contain the median, stderr and chain samples,
respectively. Otherwise `param` will be a float representing the
median of the chain samples.
`stderr` is the half width of the [15.87, 84.13] spread (similar to
standard deviation) and `chain` is an array containing the MCMC
samples for that parameter.
Notes
-----
The chain should have the shape `(iterations, nwalkers, nvary)` or
`(iterations, ntemps, nwalkers, nvary)` if parallel tempering was
employed.
The burned and thinned chain is created via:
`chain[nburn::nthin]`.
Note, if parallel tempering is employed, then only the lowest temperature
of the parallel tempering chain is processed and returned as it
corresponds to the (lowest energy) target distribution.
If `flatten is True` then the burned/thinned chain is reshaped and
`arr.reshape(-1, nvary)` is returned.
This function has the effect of setting the parameter stderr's.
"""
chain = chain[nburn::nthin]
shape = chain.shape
nvary = shape[-1]
# nwalkers = shape[1]
if len(shape) == 4:
ntemps = shape[1]
elif len(shape) == 3:
ntemps = -1
if ntemps != -1:
# PTSampler, we require the target distribution in the first row.
chain = chain[:, 0]
_flatchain = chain.reshape((-1, nvary))
if flatchain:
chain = _flatchain
flat_params = list(f_unique(flatten(objective.parameters)))
varying_parameters = objective.varying_parameters()
# set the stderr of each of the Parameters
result_list = []
if np.all([is_parameter(param) for param in flat_params]):
# zero out all the old parameter stderrs
for param in flat_params:
param.stderr = None
param.chain = None
# do the error calcn for the varying parameters and set the chain
quantiles = np.percentile(_flatchain, [15.87, 50, 84.13], axis=0)
for i, param in enumerate(varying_parameters):
std_l, median, std_u = quantiles[:, i]
param.value = median
param.stderr = 0.5 * (std_u - std_l)
# copy in the chain
param.chain = np.copy(chain[..., i])
res = MCMCResult(
name=param.name,
param=param,
median=param.value,
stderr=param.stderr,
chain=param.chain,
)
result_list.append(res)
fitted_values = np.array(varying_parameters)
# give each constrained param a chain (to be reshaped later)
constrained_params = [
param for param in flat_params if param.constraint is not None
]
for constrain_param in constrained_params:
constrain_param.chain = np.empty(chain.shape[:-1], float)
# now iterate through the varying parameters, set the values, thereby
# setting the constraint value
if len(constrained_params):
for index in np.ndindex(chain.shape[:-1]):
# iterate over parameter vectors
pvals = chain[index]
objective.setp(pvals)
for constrain_param in constrained_params:
constrain_param.chain[index] = constrain_param.value
for constrain_param in constrained_params:
quantiles = np.percentile(constrain_param.chain,
[15.87, 50, 84.13])
std_l, median, std_u = quantiles
constrain_param.value = median
constrain_param.stderr = 0.5 * (std_u - std_l)
# now reset fitted parameter values (they would've been changed by
# constraints calculations
objective.setp(fitted_values)
# the parameter set are not Parameter objects, an array was probably
# being used with BaseObjective.
else:
for i in range(nvary):
c = np.copy(chain[..., i])
median, stderr = uncertainty_from_chain(c)
res = MCMCResult(name="",
param=median,
median=median,
stderr=stderr,
chain=c)
result_list.append(res)
return result_list
def fit(self, method="L-BFGS-B", target="nll", verbose=True, **kws):
"""
Obtain the maximum log-likelihood, or log-posterior, estimate (mode)
of the objective. Maximising the log-likelihood is equivalent to
minimising chi2 in a least squares fit.
Parameters
----------
method : str
which method to use for the optimisation. One of:
- `'least_squares'`: :func:`scipy.optimize.least_squares`.
- `'L-BFGS-B'`: L-BFGS-B.
- `'differential_evolution'`:
:func:`scipy.optimize.differential_evolution`
- `'dual_annealing'`:
:func:`scipy.optimize.dual_annealing` (SciPy >= 1.2.0)
- `'shgo'`: :func:`scipy.optimize.shgo` (SciPy >= 1.2.0)
You can also choose many of the minimizers from
:func:`scipy.optimize.minimize`.
target : {'nll', 'nlpost'}, optional
Minimize the negative log-likelihood (`'nll'`) or the negative
log-posterior (`'nlpost'`). This is equivalent to maximising the
likelihood or posterior probabilities respectively.
Maximising the likelihood is equivalent to minimising chi^2 in a
least-squares fit.
This option only applies to the `differential_evolution`, `shgo`,
`dual_annealing` or `L-BFGS-B` methods.
These optimisers require lower and upper (box) bounds for each
parameter. If the `Bounds` on a parameter are not an `Interval`,
but a `PDF` specifying a statistical distribution, then the lower
and upper bounds are approximated as
``PDF.rv.ppf([0.005, 0.995])``, covering 99 % of the statistical
distribution.
verbose : bool, optional
Gives fitting progress. To see a progress bar tqdm has to be
installed.
kws : dict
Additional arguments are passed to the underlying minimization
method.
Returns
-------
result, covar : :class:`scipy.optimize.OptimizeResult`, np.ndarray
`result.x` contains the best fit parameters
`result.covar` is the covariance matrix for the fit.
`result.stderr` is the uncertainties on each of the fit parameters.
Notes
-----
If the `objective` supplies a `residuals` method then `least_squares`
can be used. Otherwise the `nll` method of the `objective` is
minimised. Use this method just before a sampling run.
If `self.objective.parameters` is a `Parameters` instance, then each
of the varying parameters has its value updated by the fit, and each
`Parameter` has a `stderr` attribute which represents the uncertainty
on the fit parameter.
The use of `dual annealing` and `shgo` requires that `scipy >= 1.2.0`
be installed.
"""
_varying_parameters = self.objective.varying_parameters()
init_pars = np.array(_varying_parameters)
_min_kws = {}
_min_kws.update(kws)
_bounds = bounds_list(self.objective.varying_parameters())
_min_kws["bounds"] = _bounds
# setup callback default
_min_kws.setdefault("callback", None)
cost = self.objective.nll
if target == "nlpost":
cost = self.objective.nlpost
# a decorator for the progress bar updater
def _callback_wrapper(callback_func, pbar):
def callback(*args, **kwds):
pbar.update(1)
if callback_func is None:
return None
else:
return callback_func(*args, **kwds)
return callback
# least_squares Trust Region Reflective by default
if method == "least_squares":
b = np.array(_bounds)
_min_kws["bounds"] = (b[..., 0], b[..., 1])
# least_squares doesn't have a callback
_min_kws.pop("callback", None)
res = least_squares(self.objective.residuals, init_pars,
**_min_kws)
# differential_evolution, dual_annealing, shgo require lower and upper
# bounds
elif method in ["differential_evolution", "dual_annealing", "shgo"]:
mini = getattr(sciopt, method)
with get_progress_bar(verbose, None) as pbar:
_min_kws["callback"] = _callback_wrapper(
_min_kws["callback"], pbar)
res = mini(cost, **_min_kws)
else:
# otherwise stick it to minimizer. Default being L-BFGS-B
_min_kws["method"] = method
_min_kws["bounds"] = _bounds
with get_progress_bar(verbose, None) as pbar:
_min_kws["callback"] = _callback_wrapper(
_min_kws["callback"], pbar)
res = minimize(cost, init_pars, **_min_kws)
# OptimizeResult.success may not be present (dual annealing)
if hasattr(res, "success") and res.success:
self.objective.setp(res.x)
# Covariance matrix estimation
covar = self.objective.covar()
errors = np.sqrt(np.diag(covar))
res["covar"] = covar
res["stderr"] = errors
# check if the parameters are all Parameter instances.
flat_params = list(f_unique(flatten(self.objective.parameters)))
if np.all([is_parameter(param) for param in flat_params]):
# zero out all the old parameter stderrs
for param in flat_params:
param.stderr = None
param.chain = None
for i, param in enumerate(_varying_parameters):
param.stderr = errors[i]
# need to touch up the output to check we leave
# parameters as we found them
self.objective.setp(res.x)
return res
def sample(
self,
steps,
nthin=1,
random_state=None,
f=None,
callback=None,
verbose=True,
pool=-1,
):
"""
Performs sampling from the objective.
Parameters
----------
steps : int
Collect `steps` samples into the chain. The sampler will run a
total of `steps * nthin` moves.
nthin : int, optional
Each chain sample is separated by `nthin` iterations.
random_state : {int, `np.random.RandomState`, `np.random.Generator`}
If `random_state` is not specified the `~np.random.RandomState`
singleton is used.
If `random_state` is an int, a new ``RandomState`` instance is
used, seeded with random_state.
If `random_state` is already a ``RandomState`` or a ``Generator``
instance, then that object is used.
Specify `random_state` for repeatable minimizations.
f : file-like or str
File to incrementally save chain progress to. Each row in the file
is a flattened array of size `(nwalkers, ndim)` or
`(ntemps, nwalkers, ndim)`. There are `steps` rows in the
file.
callback : callable
callback function to be called at each iteration step. Has the
signature `callback(coords, logprob)`.
verbose : bool, optional
Gives updates on the sampling progress
pool : int or map-like object, optional
If `pool` is an `int` then it specifies the number of threads to
use for parallelization. If `pool == -1`, then all CPU's are used.
If pool is a map-like callable that follows the same calling
sequence as the built-in map function, then this pool is used for
parallelisation.
Notes
-----
Please see :class:`emcee.EnsembleSampler` for its detailed behaviour.
>>> # we'll burn the first 500 steps
>>> fitter.sample(500)
>>> # after you've run those, then discard them by resetting the
>>> # sampler.
>>> fitter.sampler.reset()
>>> # Now collect 40 steps, each step separated by 50 sampler
>>> # generations.
>>> fitter.sample(40, nthin=50)
One can also burn and thin in `Curvefitter.process_chain`.
"""
self._check_vars_unchanged()
# setup a random number generator
rng = check_random_state(random_state)
if self._state is None:
self.initialise(random_state=rng)
# for saving progress to file
def _callback_wrapper(state, h=None):
if callback is not None:
callback(state.coords, state.log_prob)
if h is not None:
h.write(" ".join(map(str, state.coords.ravel())))
h.write("\n")
# remove chains from each of the parameters because they slow down
# pickling but only if they are parameter objects.
flat_params = f_unique(flatten(self.objective.parameters))
flat_params = [param for param in flat_params if is_parameter(param)]
# zero out all the old parameter stderrs
for param in flat_params:
param.stderr = None
param.chain = None
# make sure the checkpoint file exists
if f is not None:
with possibly_open_file(f, "w") as h:
# write the shape of each step of the chain
h.write("# ")
shape = self._state.coords.shape
h.write(", ".join(map(str, shape)))
h.write("\n")
# set the random state of the sampler
# normally one could give this as an argument to the sample method
# but PTSampler didn't historically accept that...
if isinstance(rng, np.random.RandomState):
rstate0 = rng.get_state()
self._state.random_state = rstate0
self.sampler.random_state = rstate0
# using context manager means we kill off zombie pool objects
# but does mean that the pool has to be specified each time.
with MapWrapper(pool) as g, possibly_open_file(f, "a") as h:
# these kwargs are provided to the sampler.sample method
kwargs = {"iterations": steps, "thin": nthin}
# if you're not creating more than 1 thread, then don't bother with
# a pool.
if isinstance(self.sampler, emcee.EnsembleSampler):
if pool == 1:
self.sampler.pool = None
else:
self.sampler.pool = g
else:
kwargs["mapper"] = g
# new emcee arguments
sampler_args = getargspec(self.sampler.sample).args
if "progress" in sampler_args and verbose:
kwargs["progress"] = True
verbose = False
if "thin_by" in sampler_args:
kwargs["thin_by"] = nthin
kwargs.pop("thin", 0)
# perform the sampling
for state in self.sampler.sample(self._state, **kwargs):
self._state = state
_callback_wrapper(state, h=h)
if isinstance(self.sampler, emcee.EnsembleSampler):
self.sampler.pool = None
# sets parameter value and stderr
return process_chain(self.objective, self.chain)
def nDim(self):
if self.nDimensions is None:
self.nDimensions = len(list(p for p
in f_unique(flatten(self.objective.parameters)) if p.vary ))
return self.nDimensions
