Source code for magni.cs.reconstruction.sl0._sigma_start
"""
..
Copyright (c) 2015-2017, Magni developers.
All rights reserved.
See LICENSE.rst for further information.
Module providing functions for calculating the starting value of sigma used in
the Smoothed l0 algorithms.
Routine listings
----------------
calculate_using_fixed(var)
Calculate the fixed sigma value.
calculate_using_reciprocal(var)
Calculate a sigma value in a 'reciprocal' way.
get_function_handle(method)
Return a function handle to a given calculation method.
"""
from __future__ import division
[docs]def wrap_calculate_using_fixed(var):
"""
Arguments wrapper for calculate_using_fixed.
"""
convert = var['convert']
sigma_start = convert(var['param']['sigma_start_fixed'])
def calculate_using_fixed():
"""
Calculate the fixed sigma value.
Parameters
----------
var : dict
Dictionary of variables used in the calculation of the sigma
value.
Returns
-------
sigma : float
The sigma value to be used in the SL0 algorithm.
"""
return sigma_start
return calculate_using_fixed
[docs]def wrap_calculate_using_reciprocal(var):
"""
Arguments wrapper for calculate_using_reciprocal.
"""
convert = var['convert']
delta = var['A'].shape[0] / var['A'].shape[1]
factor = convert(var['param']['sigma_start_reciprocal'])
def calculate_using_reciprocal():
"""
Calculate a sigma value in a 'reciprocal' way.
Parameters
----------
var : dict
Dictionary of variables used in the calculation of the sigma value.
Returns
-------
sigma : float
The sigma value to be used in the SL0 algorithm.
"""
return 1 / (factor * delta)
return calculate_using_reciprocal
[docs]def get_function_handle(method, var):
"""
Return a function handle to a given calculation method.
Parameters
----------
method : str
Identifier of the calculation method to return a handle to.
var : dict
Local variables needed in the sigma method.
Returns
-------
f_handle : function
Handle to the calculation method defined in this globals scope.
"""
return globals()['wrap_calculate_using_' + method](var)