/Users/sean/workspace/ContribSLIMpy/slimpy_contrib/ana/utils/thresholds.py

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"""
Theshold schemes to pass to landweber solver
"""

__copyright__ = """
Copyright 2008 Sean Ross-Ross
"""
__license__ =  """
This file is part of SLIMpy .

SLIMpy is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

SLIMpy is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with SLIMpy . If not, see <http://www.gnu.org/licenses/>.
"""

from slimpy_base.SLIMmath.Steppers import OneDimStepN

class threshobj( object ):
    """
    Base class for the shreshold schemes.
    
    """
    def __init__( self ):
        pass
    
    def choose( self, param=0.007, **kargs ):
        """
        choose must be called with the key word param
        """
        return param
    
class LinearCooling( threshobj ):
    """
    Linear Threshold scheme for landweber
    """
    def __init__( self, lambdaMax, lambdaMin, OuterN ):
        self.lambdaMax = lambdaMax
        self.lambdaMin = lambdaMin
        self.OuterN = OuterN
        self.prev_i = None
        stepper = OneDimStepN( lambdaMax, lambdaMin, OuterN )
        self.slist = list(stepper) 
        self.stepper = self.slist.__iter__()
        
        
    def choose( self, coefs, i, OuterN, **kargs ):
        """
        """
        if self.prev_i != i:
#            print self.prev_i , i
            self.prev_i = i
            self.step  =self.stepper.next( )
            
        return self.step

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