def compute_fit(self):
self._polychord_output = None
data = self._observed.spectrum
datastd = self._observed.errorBar
sqrtpi = np.sqrt(2 * np.pi)
ndim = len(self.fitting_parameters)
def polychord_loglike(cube):
# log-likelihood function called by polychord
fit_params_container = np.array(
[cube[i] for i in range(len(self.fitting_parameters))])
chi_t = self.chisq_trans(fit_params_container, data, datastd)
# print('---------START---------')
# print('chi_t',chi_t)
# print('LOG',loglike)
loglike = -np.sum(np.log(datastd * sqrtpi)) - 0.5 * chi_t
return loglike, [0.0]
def polychord_uniform_prior(hypercube):
# prior distributions called by polychord. Implements a uniform prior
# converting parameters from normalised grid to uniform prior
# print(type(cube))
cube = [0.0] * ndim
for idx, bounds in enumerate(self.fit_boundaries):
# print(idx,self.fitting_parameters[idx])
bound_min, bound_max = bounds
cube[idx] = (hypercube[idx] *
(bound_max - bound_min)) + bound_min
#print('CUBE idx',cube[idx])
# print('-----------')
return cube
status = None
datastd_mean = np.mean(datastd)
settings = PolyChordSettings(ndim, 1)
settings.nlive = ndim * 25
settings.num_repeats = ndim * 5
settings.do_clustering = self.do_clustering
settings.num_repeats = ndim
settings.precision_criterion = self.evidence_tolerance
settings.logzero = -1e70
settings.read_resume = self.resume
settings.base_dir = self.dir_polychord
settings.file_root = '1-'
self.warning('Number of dimensions {}'.format(ndim))
self.warning('Fitting parameters {}'.format(self.fitting_parameters))
self.info('Beginning fit......')
pypolychord.run_polychord(polychord_loglike, ndim, 1, settings,
polychord_uniform_prior)
self._polychord_output = self.store_polychord_solutions()
print(self._polychord_output)
def polychord_sampler(self):
import pypolychord
from pypolychord.settings import PolyChordSettings
from pypolychord.priors import UniformPrior, GaussianPrior
ndim = len(self.params.p0)
nder = 0
# Log-likelihood compliant with PolyChord's input
def likelihood(theta):
return self.lnlike(theta), [0]
def prior(hypercube):
prior = []
for h, pr in zip(hypercube, self.params.p_free_priors):
if pr[1] == 'Gaussian':
prior.append(
GaussianPrior(float(pr[2][0]), float(pr[2][1]))(h))
else:
prior.append(
UniformPrior(float(pr[2][0]), float(pr[2][2]))(h))
return prior
# Optional dumper function giving run-time read access to
# the live points, dead points, weights and evidences
def dumper(live, dead, logweights, logZ, logZerr):
print("Last dead point:", dead[-1])
settings = PolyChordSettings(ndim, nder)
settings.base_dir = self.get_output(
'param_chains')[:-4] # Remove ".npz"
settings.file_root = 'pch'
settings.nlive = self.config['nlive']
settings.num_repeats = self.config['nrepeat']
settings.do_clustering = False # Assume unimodal posterior
settings.boost_posterior = 10 # Increase number of posterior samples
settings.nprior = 200 # Draw nprior initial prior samples
settings.maximise = True # Maximize posterior at the end
settings.read_resume = False # Read from resume file of earlier run
settings.feedback = 2 # Verbosity {0,1,2,3}
output = pypolychord.run_polychord(likelihood, ndim, nder, settings,
prior, dumper)
return output
def run_polychord(num_live_points):
try:
import pypolychord
from pypolychord.settings import PolyChordSettings
from pypolychord.priors import UniformPrior
except:
raise ImportError("Polychord not installed.\nRun `git clone https://github.com/PolyChord/PolyChordLite.git \ncd PolyChordLite\npython setup.py install`.")
def likelihood(theta):
""" Simple Gaussian Likelihood"""
nDims = len(theta)
r2 = sum(theta**2)
logL = -log(2*pi*sigma*sigma)*nDims/2.0
logL += -r2/2/sigma/sigma
return logL, [r2]
def prior(hypercube):
""" Uniform prior from [-1,1]^D. """
return UniformPrior(-1, 1)(hypercube)
def dumper(live, dead, logweights, logZ, logZerr):
return
# print("Last dead point:", dead[-1])
settings = PolyChordSettings(ndims, 1)
settings.file_root = 'gaussian'
settings.nlive = num_live_points
settings.do_clustering = True
settings.read_resume = False
t0 = default_timer()
output = pypolychord.run_polychord(likelihood, ndims, 1, settings, prior, dumper)
run_time = default_timer() - t0
print("polychord log(Z):", output.logZ)
return run_time
# In this module I'm going to investigate the effect of the so-called
# Lasenby parameter as well as the effects of proper prior
# repartitioning, and benchmark to see a speedup.
# Vanilla
mu = numpy.array([1.0, 2.5])
cov = numpy.array([[1.0, 0.6], [0.6, 1.0]])
nDims = mu.size
settings = PolyChordSettings(nDims, 0)
settings.file_root = 'vanilla'
settings.nlive = 10**3
settings.read_resume = False
settings.do_clustering = True
settings.feedback = 0
def gaussian_likelihood(theta):
invSig = numpy.linalg.inv(cov)
norm = numpy.linalg.slogdet(2 * numpy.pi * cov)[1] / 2
logL = -norm - (theta - mu) @ invSig @ (theta - mu) / 2
return logL, []
def uniform_prior(point_in_hypercube):
return pypolychord.priors.UniformPrior(-20, 20)(point_in_hypercube)
# try:
def prior(hypercube):
""" Priors for each parameter. """
theta = [0.0] * nDims
for i, x in enumerate(hypercube):
theta[i] = priordict[parnames[i]].ppf(x)
return theta
# Define PolyChord settings
settings = PolyChordSettings(
nDims,
nDerived,
)
settings.do_clustering = args_params.noclust
settings.nlive = nDims * args_params.nlive
settings.base_dir = base_dir
settings.file_root = 'hd40307_k{}'.format(nplanets) # modelpath[12:-3]
settings.num_repeats = nDims * args_params.nrep
settings.precision_criterion = args_params.prec
settings.read_resume = False
# Change settings if resume is true
if args_params.resume:
settings.read_resume = args_params.resume
settings.base_dir = dirname + prev_run
# Run PolyChord
output = PPC.run_polychord(logLikelihood, nDims, nDerived, settings, prior)
def run_polychord(loglikelihood, prior, dumper, nDims, nlive, root, ndump,
num_repeats):
"""Run PolyChord.
See https://arxiv.org/abs/1506.00171 for more detail
Parameters
----------
loglikelihood: :obj:`callable`
probability function taking a single parameter:
- theta: numpy.array
physical parameters, `shape=(nDims,)`
returning a log-likelihood (float)
prior: :obj:`callable`
tranformation function taking a single parameter
- cube: numpy.array
hypercube parameters, `shape=(nDims,)`
returning physical parameters (`numpy.array`)
dumper: :obj:`callable`
access function called every nlive iterations giving a window onto
current live points. Single parameter, no return:
- live:
`numpy.array of` live parameters and loglikelihoods,
`shape=(nlive,nDims+1)`
nDims: int
Dimensionality of sampling space
nlive: int
Number of live points
root: str
base name for output files
ndump: int
How many iterations between dumper function calls
num_repeats: int
Length of chain to generate new live points
"""
import pypolychord
from pypolychord.settings import PolyChordSettings
nDerived = 0
settings = PolyChordSettings(nDims, nDerived)
settings.base_dir = os.path.dirname(root)
settings.file_root = os.path.basename(root)
settings.nlive = nlive
settings.num_repeats = num_repeats
settings.do_clustering = True
settings.read_resume = False
settings.compression_factor = numpy.exp(-float(ndump)/nlive)
settings.precision_criterion = 0.01
def polychord_loglikelihood(theta):
return loglikelihood(theta), []
def polychord_dumper(live, dead, logweights, logZ, logZerr):
dumper(live[:, :-2], live[:, -1], dead[:, :-2], dead[:, -1])
pypolychord.run_polychord(polychord_loglikelihood, nDims, nDerived,
settings, prior, polychord_dumper)
def pc(test_statistic,
transform,
n_dim,
observed,
n_live=100,
base_dir="chains/",
file_root="pc_",
do_clustering=False,
resume=False,
ev_data=False,
feedback=0,
**kwargs):
"""
Nested sampling with PC
"""
# copy key word arguments to settings object
settings = PolyChordSettings(n_dim, 0, **kwargs)
settings.nfail = n_live
settings.precision_criterion = 0.
settings.read_resume = resume
settings.base_dir = base_dir
settings.file_root = file_root
settings.nlive = n_live
settings.logLstop = observed
settings.do_clustering = do_clustering
settings.feedback = feedback
loglike = pc_wrap(test_statistic)
output = pypolychord.run_polychord(loglike, n_dim, 0, settings, transform,
dumper(0, observed))
# get number of calls directly
calls = output.nlike
# get log X from resume file
label = "=== local volume -- log(<X_p>) ==="
log_xp = None
res_name = "{}/{}.resume".format(base_dir, file_root)
with open(res_name) as res_file:
for line in res_file:
if line.strip() == label:
next_line = res_file.readline()
log_xp = np.array([float(e) for e in next_line.split()])
break
else:
raise RuntimeError("didn't find {}".format(label))
log_x = logsumexp(log_xp)
n_iter = -log_x * n_live
if not ev_data:
return Result.from_ns(n_iter, n_live, calls)
# get ev data
ev_name = "{}/{}_dead.txt".format(base_dir, file_root)
ev_data = np.genfromtxt(ev_name)
test_statistic = ev_data[:, 0]
log_x = -np.arange(0, len(test_statistic), 1.) / n_live
log_x_delta = np.sqrt(-log_x / n_live)
return Result.from_ns(n_iter, n_live,
calls), [test_statistic, log_x, log_x_delta]
def run_polychord(loglikelihood, prior, dumper, nDims, nlive, root,
num_repeats):
""" Wrapper function to run PolyChord
See https://arxiv.org/abs/1506.00171 for more detail
Parameters
----------
loglikelihood: callable
probability function taking a single parameter:
- theta: numpy.array
physical parameters, `shape=(nDims,)`
returning a log-likelihood (float)
prior: callable
tranformation function taking a single parameter
- cube: numpy.array
hypercube parameters, `shape=(nDims,)`
returning physical parameters (`numpy.array`)
dumper: callable
access function called every nlive iterations giving a window onto
current live points. Single parameter, no return:
- live: numpy.array
live parameters and loglikelihoods, `shape=(nlive,nDims+1)`
nDims: int
Dimensionality of sampling space
nlive: int
Number of live points
root: str
base name for output files
num_repeats: int
Length of chain to generate new live points
"""
import pypolychord
from pypolychord.settings import PolyChordSettings
basedir = os.path.dirname(root)
cluster_dir = os.path.join(basedir,'clusters')
with suppress(Exception): os.makedirs(cluster_dir)
nDerived = 0
settings = PolyChordSettings(nDims, nDerived)
settings.base_dir = os.path.dirname(root)
settings.file_root = os.path.basename(root)
settings.nlive = nlive
settings.num_repeats = num_repeats
settings.do_clustering = True
settings.read_resume = False
def polychord_loglikelihood(theta):
return loglikelihood(theta), []
def polychord_dumper(live, dead, logweights, logZ, logZerr):
dumper(live[:, :-1])
pypolychord.run_polychord(polychord_loglikelihood, nDims, nDerived,
settings, prior, polychord_dumper)