#  _________________________________________________________________________
#
#  Pyomo: Python Optimization Modeling Objects
#  Copyright (c) 2014 Sandia Corporation.
#  Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
#  the U.S. Government retains certain rights in this software.
#  This software is distributed under the BSD License.
#  _________________________________________________________________________

from __future__ import division

import math
import os
import random

import pyomo.util.plugin
from pyomo.pysp import phextension
from pyomo.pysp.phutils import *
from pyomo.pysp.phsolverserverutils import \
    transmit_external_function_invocation_to_worker
from pyomo.pysp.generators import \
    scenario_tree_node_variables_generator_noinstances
from pyomo.core.base import *

import six
from six import iteritems
from six.moves import xrange

has_yaml = False
try:
    import yaml
    has_yaml = True
except:
    pass

#
# Create a dictionary mapping scenario tree id to
# variable bounds
#
def collect_node_variable_bounds(tree_node):
    assert tree_node._variable_datas is not None
    var_bounds = {}
    for variable_id, vardatas in iteritems(tree_node._variable_datas):
        vardata = vardatas[0][0]
        if not vardata.is_expression():
            var_bounds[variable_id] = (vardata.lb, vardata.ub)
        else:
            # Expression
            var_bounds[variable_id] = (None,None)

    return var_bounds

# This function will be executed on a phsolverserver using
# the transmit_external_function_invocation_to_worker utility
def external_collect_variable_bounds(ph,
                                     scenario_tree,
                                     scenario_or_bundle,
                                     node_list):

    variable_bounds = {}
    for node_name in node_list:
        tree_node = scenario_tree._tree_node_map[node_name]
        variable_bounds[node_name] = collect_node_variable_bounds(tree_node)

    return variable_bounds

#==================================================
class wwphextension(pyomo.util.plugin.SingletonPlugin):

    pyomo.util.plugin.implements(phextension.IPHExtension)
    
    # the below is a hack to get this extension into the
    # set of IPHExtension objects, so it can be queried
    # automagically by PH.
    pyomo.util.plugin.alias("WWPHExtension")

    def __init__(self, *args, **kwds):

        # TBD - migrate all of the self attributes defined on-the-fly
        #       in the post-post-initialization routine here!
        self._valid_suffix_names = [\
            'Iter0FixIfConvergedAtLB',   # has default
            'Iter0FixIfConvergedAtUB',   # has default
            'Iter0FixIfConvergedAtNB',   # has default
            'CostForRho',
            'FixWhenItersConvergedAtLB', # has default
            'FixWhenItersConvergedAtUB', # has default
            'FixWhenItersConvergedAtNB', # has default
            'CanSlamToLB',               # has default
            'CanSlamToMin',              # has default
            'CanSlamToUB',               # has default
            'CanSlamToMax',              # has default
            'CanSlamToAnywhere',         # has default
            'SlammingPriority']
        self._AnnotationTypes = {}
        # Real
        self._AnnotationTypes['going_price'] = None
        # String
        self._AnnotationTypes['obj_effect_family_name'] = None
        # Real
        self._AnnotationTypes['obj_effect_family_factor'] = None
        # non-negative int
        self._AnnotationTypes['decision_hierarchy_level'] = None
        self._AnnotationTypes['feasibility_direction'] = \
            ['down', 'up', 'either', 'None']
        # int
        self._AnnotationTypes['relax_int'] = None
        # int
        self._AnnotationTypes['reasonable_int'] = None
        # int
        self._AnnotationTypes['low_int'] = None

        assert len(set(self._valid_suffix_names).\
                   intersection(self._AnnotationTypes.keys())) == 0

        self._suffixes = {}
        for name in self._valid_suffix_names:
            self._suffixes[name] = {}
        for name in self._AnnotationTypes:
            self._suffixes[name] = {}

        # formerly known as self._suffixes["my_stage"]
        self._variable_stage = {}

        self._configuration_filename = None
        self._suffix_filename = None
        self._annotation_filename = None

        # we track various actions performed by this extension following a 
        # PH iteration - useful for reporting purposes, and for other plugins
        # to react to.
        self.variables_with_detected_cycles = []
        self.variable_fixed = False

    def _parse_yaml_file(self, ph, filename):

        if not has_yaml:
            raise RuntimeError("***WW PH Extension: The PyYAML module is required "
                               "to load file: "+filename)

        with open(filename) as f:
            config_data = yaml.load(f)

        for node_or_stage_name, variable_dicts in iteritems(config_data):

            # find the node or stage object in the scenario tree
            # and convert it to a list of nodes
            node_list = None
            for stage in ph._scenario_tree._stages[:-1]:
                if node_or_stage_name == stage._name:
                    node_list = stage._tree_nodes
                    break
                else:
                    for tree_node in stage._tree_nodes:
                        if tree_node._name == node_or_stage_name:
                            node_list = [tree_node]
                            break
                    if node_list is not None:
                        break

            if len(node_list) == 0:
                raise RuntimeError("***WW PH Extension: %s does not name an "
                                   "existing non-leaf Stage or Node in the "
                                   "scenario tree" % node_or_stage_name)
            
            for variable_string, variable_config_data in iteritems(variable_dicts):

                variable_name = None
                index_template = None
                if isVariableNameIndexed(variable_string):
                    variable_name, index_template = \
                        extractVariableNameAndIndex(variable_string)
                else:
                    variable_name = variable_string
                    index_template = None

                match_variable_ids = {}
                for node in node_list:
                    node_match_variable_ids = match_variable_ids[node._name] = []
                    for variable_id, (name,index) in iteritems(node._variable_ids):
                        if (variable_name == name):
                            if (index_template is None) and (index != None):
                                raise RuntimeError("***WW PH Extension: Illegal "
                                                   "match template="
                                                   +variable_string+" specified "
                                                   "in file="+filename)
                            if indexMatchesTemplate(index, index_template):
                                node_match_variable_ids.append(variable_id)
                # we shouldn't have any duplicates or empties
                for node in node_list:
                    assert len(set(match_variable_ids)) == len(match_variable_ids)
                    if len(match_variable_ids[node._name]) == 0:
                        raise RuntimeError("No variables matching string '%s' "
                                           "were found in scenario tree node %s"
                                           % (variable_string, node._name))

                for config_name, config_value in iteritems(variable_config_data):
                    
                    yield config_name, config_value, match_variable_ids


#==================================================

    def process_suffix_file(self, ph):

        self.slam_list = []

        if self._suffix_filename is None:
            return

        if os.path.exists(self._suffix_filename) is False:
            raise RuntimeError("***WW PH Extension: The suffix "
                               "file "+self._suffix_filename+
                               " either does not exist or cannot be read")

        print("WW PH Extension: Loading variable suffixes "
              "from file="+self._suffix_filename)

        for suffix_name, suffix_value, variable_ids in \
              self._parse_yaml_file(ph, self._suffix_filename):

            if suffix_name not in self._valid_suffix_names:
                raise RuntimeError("***WW PH Extension: %s is not a valid "
                                   "suffix name" % (suffix_name))

            # decide what type of suffix value we're dealing with.
            is_int = False
            is_bool = False
            converted_value = None
            try:
                converted_value = bool(suffix_value)
                is_bool = True
            except ValueError:
                pass
            try:
                converted_value = int(suffix_value)
                is_int = True
            except ValueError:
                pass

            if (not is_int) and (not is_bool):
                raise RuntimeError("WW PH Extension unable to deduce type of data "
                                   "referenced in ww ph extension suffix file"
                                   "="+self._suffix_filename+"; value="
                                   +suffix_value)

            self_suffix_dict = self._suffixes[suffix_name]
            for node_name, node_variable_ids in iteritems(variable_ids):
                for variable_id in node_variable_ids:
                    self_suffix_dict[variable_id] = converted_value

        self.slam_list = list(self._suffixes["SlammingPriority"].keys())

        if self.slam_list != []:
            #
            # We have been ordering this list largest slamming
            # priority to smallest (meaning a larger value for
            # slamming priority implies we're first in line to get
            # fixed). I can't decide if that is the most natural way
            # to interpret this, but I'm leaving it as it will likely
            # change solutions if changed.
            #
            self.slam_list.sort(key=self._suffixes["SlammingPriority"].get,
                                reverse=True)

    def process_annotation_file(self, ph):
        # note: these suffixes can have a string value very similar to
        # suffixes, except for the following: annotation names are
        # from a restricted list, and annotations can have various
        # types that might depend on the name of the annotation
        # not all type checking will be done here, but some might be

        self._obj_family_normalized_rho = {}

        if self._annotation_filename is None:
            return

        if os.path.exists(self._annotation_filename) is False:
            raise RuntimeError("***WW PH Extension: The annotation file "
                               +self._annotation_filename+" either does "
                               "not exist or cannot be read")

        print("WW PH Extension: Loading variable annotations from "
              "file="+self._annotation_filename)

        for annotation_name, annotation_value, variable_ids in \
              self._parse_yaml_file(ph, self._annotation_filename):

            # check for some input errors
            if annotation_name not in self._AnnotationTypes:
                print("Error encountered.")
                print("Here are the annotations that can be given "
                      "(they are case sensitive):")
                for i in self._AnnotationTypes:
                    print(i)
                raise RuntimeError("WW ph extension annotation file="
                                   +self._annotation_filename+"; "
                                   "contains unknown annotation: "+annotation_name)

            # check for some more input errors
            if self._AnnotationTypes[annotation_name] is not None:
                if annotation_value not in self._AnnotationTypes[annotation_name]:
                    raise RuntimeError("WW ph extension annotation file="
                                       +self._annotation_filename+"; "
                                       "contains unknown annotation value="
                                       +annotation_value+" for: "+annotation_name)

            # if this is a new obj effect family, then we need new maps
            if annotation_name == 'obj_effect_family_name':
                if annotation_value not in self._obj_family_normalized_rho:
                    self._obj_family_normalized_rho[annotation_value] = 0.0

            self_suffix_dict = self._suffixes[annotation_name]
            for node_name, node_variable_ids in iteritems(variable_ids):
                for variable_id in node_variable_ids:
                    self_suffix_dict[variable_id] = converted_value

    #
    # Store the variable bounds on the tree node by variable id
    # If this is parallel ph, then we need to do this by transmitting
    # an external function invocation that collects the variable
    # bounds from a given list of node names. We do this in such
    # a way as to minimize the amount of data we need to transfer
    # (e.g., in the case of a two stage problem, we request information
    # about the root node from only one of the PH solver servers)
    #

    def _collect_variable_bounds(self,ph):

        if not isinstance(ph._solver_manager,
                          pyomo.solvers.plugins.smanager.phpyro.SolverManager_PHPyro):

            for stage in ph._scenario_tree._stages[:-1]:

                for tree_node in stage._tree_nodes:

                    tree_node._variable_bounds = \
                        collect_node_variable_bounds(tree_node)

        else:

            nodes_needed = {}
            if ph._scenario_tree.contains_bundles():
                for tree_node in ph._scenario_tree._tree_nodes:
                    if not tree_node.is_leaf_node():
                        representative_scenario = tree_node._scenarios[0]._name
                        representative_bundle = None
                        for bundle in ph._scenario_tree._scenario_bundles:
                            if representative_scenario in bundle._scenario_names:
                                representative_bundle = bundle._name
                                break
                        assert representative_bundle != None
                        if representative_bundle not in nodes_needed:
                            nodes_needed[representative_bundle] = \
                                [tree_node._name]
                        else:
                            nodes_needed[representative_bundle].\
                                append(tree_node._name)
            else:
                for tree_node in ph._scenario_tree._tree_nodes:
                    if not tree_node.is_leaf_node():
                        representative_scenario = tree_node._scenarios[0]._name
                        if representative_scenario not in nodes_needed:
                            nodes_needed[representative_scenario] = \
                                [tree_node._name]
                        else:
                            nodes_needed[representative_scenario].\
                                append(tree_node._name)

            action_handle_map = {}
            for object_name, node_list in iteritems(nodes_needed):
                function_args = (node_list,)
                new_action_handle = \
                    transmit_external_function_invocation_to_worker(
                        ph,
                        object_name,
                        "pyomo.pysp.plugins.wwphextension",
                        "external_collect_variable_bounds",
                        return_action_handle=True,
                        function_args=function_args)

                action_handle_map[new_action_handle] = object_name

            num_results_so_far = 0
            num_results = len(action_handle_map)
            while (num_results_so_far < num_results):
                ah = ph._solver_manager.wait_any()
                results = ph._solver_manager.get_results(ah)
                object_name = action_handle_map[ah]
                for node_name, node_bounds in iteritems(results):
                    tree_node = ph._scenario_tree._tree_node_map[node_name]
                    tree_node._variable_bounds = node_bounds
                num_results_so_far += 1

    def reset(self, ph):
        self.__init__()

    def pre_ph_initialization(self,ph):
        # we don't need to intefere with PH initialization.
        pass

    def post_instance_creation(self, ph):
        # we don't muck with the instances.
        pass

    def post_ph_initialization(self, ph):
        
        # Be verbose (even if ph is not)
        self.Verbose = False

        # set up "global" record keeping.
        self.cumulative_discrete_fixed_count = 0
        self.cumulative_continuous_fixed_count = 0

        # we always track convergence of continuous variables, but we
        # may not want to fix/slam them.
        self.fix_continuous_variables = False

        # there are occasions where we might want to fix any values at
        # the end of the run if the scenarios agree - even if the
        # normal fixing criterion (e.g., converged for N iterations)
        # don't apply. one example is when the term-diff is 0, at
        # which point you really do have a solution. currently only
        # applies to discrete variables.
        self.fix_converged_discrete_variables_at_exit = False

        # set up the mipgap parameters (zero means ignore)
        # note:
        # because we lag one iteration, the final will be less than
        # requested initial and final refer to PH iteration 1 and PH
        # iteration X, where X is the iteration at which the
        # convergence metric hits 0.
        self.Iteration0MipGap = 0.0
        self.InitialMipGap = 0.0
        self.FinalMipGap = 0.0
        self.MipGapExponent = 1.0 # linear by default

        # the comparison tolerance for two hashed weight values.
        # by default, 1e-5 should suffice. however, depending on
        # solution structure and mipgap, non-default values may
        # be necessary. 
        # IMPT (and new): this value is interpreted as a percentage,
        # i.e., a value of 1 indicates a 1% difference in hash values
        # is sufficient to trigger a cycle detection claim.
        self.WHashComparisonTolerance = 1e-5

        # it is occasionally useful to see the W hash histories
        # when a cycle is detected, to examine patterns in support
        # of identifying an appropriate comparison tolerance. 
        # defaults to False.
        self.ReportCycleWHashDetail = False

        # use the convergence metric value from iteration 0 as the
        # basis for scaling the mipgap in subsequent iterations. if
        # set to False, we instaed start scaling from the convergence
        # metric value following iteration 1. the latter arguably
        # makes more sense, as it accounts for weights and such, i.e.,
        # some sub-prolem interactions.
        self.StartMipGapFromIter0Metric = True 

        # when cylcing is detected for a variable, the 
        # rho will be multiplied by this factor.
        # NOTE: 1 is a no-op
        self.RhoReductionFactor = 1.0

        # when cycling is detected for a variable, the
        # rho on a per scenario basis will be perturbed
        # by the following factor (uniformly sampled,
        # plus/minus this factor). 
        # NOTE: 0 is a no-op
        self.ScenarioRhoPerturbation = 0.0

        # "Read" the defaults for parameters that control fixing
        # (these defaults can be overridden at the variable level) for
        # all six of these, zero means don't do it.
        self.Iter0FixIfConvergedAtLB = 0 # 1 or 0
        self.Iter0FixIfConvergedAtUB = 0  # 1 or 0
        self.Iter0FixIfConvergedAtNB = 0  # 1 or 0 (converged to a non-bound)
        # TBD: check for range errors for all six of these
        self.FixWhenItersConvergedAtLB = 10
        self.FixWhenItersConvergedAtUB = 10
        # converged to a non-bound
        self.FixWhenItersConvergedAtNB = 12
        self.FixWhenItersConvergedContinuous = 0

        # "default" slamming parms:
        self.CanSlamToLB = False
        self.CanSlamToMin = False
        self.CanSlamToAnywhere = True
        self.CanSlamToMax = False
        self.CanSlamToUB = False
        # zero means "slam at will"
        self.PH_Iters_Between_Cycle_Slams = 1
        # this is a simple heuristic - and probably a bad one!
        self.SlamAfterIter = len(ph._scenario_tree._stages[-1]._tree_nodes) 
        # slam only if the convergence metric is not improving. defaults to
        # false. in general, if the convergence metric is improving, then
        # we would like PH to enforce non-antipicativity on its own. that 
        # said, there are counter-examples - particularly when we have
        # continuous variables.
        self.SlamOnlyIfNotConverging = False

        # default params associated with fixing due to weight vector oscillation.
        self.CheckWeightOscillationAfterIter = 0
        self.FixIfWeightOscillationCycleLessThan = 10        

        # flags enabling various rho computation schemes.
        self.ComputeRhosWithpreSEP = False
        self.ComputeRhosWithSEP = False
        self.RhosSEPMult = None  # the user needs an error if not set...

        self.CycleLengthSlamThreshold = \
            len(ph._scenario_tree._stages[-1]._tree_nodes)
        self.W_hash_history_len = max(100, self.CycleLengthSlamThreshold+1)

        # do I report potential cycles, i.e., those too short to base
        # slamming on?
        self.ReportPotentialCycles = False

        # end of parms

        self._last_slam_iter = -1    # dynamic

        # constants for W vector hashing (low cost rand() is all we need)
        # note: July 09, dlw is planning to eschew pre-computed random
        #   vector (dlw April 2014: "huh?")
        # another note: the top level reset is OK, but really it should
        #   done way down at the index level with a serial number (stored)
        #   to avoid correlated hash errors
        # the hash seed was deleted in 1.1 and we seed with the

        # we will reset for dynamic rand vector generation
        self.W_hash_seed = 17
        # current rand
        self.W_hash_rand_val = self.W_hash_seed
        # a,b, and c are for a simple generator
        self.W_hash_a = 1317
        self.W_hash_b = 27699
        # that period should be usually long enough for us!
        # (assuming fewer than c scenarios)
        self.W_hash_c = 131072

        my_stage_suffix = self._variable_stage

        # set up tree storage for statistics that we care about tracking.
        for stage in ph._scenario_tree._stages[:-1]:

            for tree_node in stage._tree_nodes:

                # we're adding a lot of statistics / tracking data to
                # each tree node.  these are all maps from variable
                # name to a parameter that tracks the corresponding
                # information.
                tree_node._num_iters_converged = \
                    dict.fromkeys(tree_node._variable_ids,0)
                tree_node._last_converged_val = \
                    dict.fromkeys(tree_node._variable_ids,0.5)
                tree_node._w_hash = \
                    dict(((variable_id,ph_iter),0) \
                         for variable_id in tree_node._variable_ids \
                         for ph_iter in ph._iteration_index_set)
                # sign vector for weights at the last PH iteration
                tree_node._w_sign_vector = \
                    dict.fromkeys(tree_node._variable_ids,[])
                # the number of iterations since the last flip in the
                # sign (TBD - of any scenario in the vector)?
                tree_node._w_last_sign_flip_iter = \
                    dict.fromkeys(tree_node._variable_ids,0)

                my_stage_suffix.update((variable_id,stage) \
                                       for variable_id in tree_node._variable_ids)

        if self._configuration_filename is not None:
            if os.path.exists(self._configuration_filename) is True:
                print("WW PH Extension: Loading user-specified configuration "
                      "from file=" + self._configuration_filename)
                try:
                    if six.PY3:
                        with open(self._configuration_filename,"rb") as f:
                            code = compile(f.read(), self._configuration_filename, 'exec')
                            exec(code) in globals(), locals()
                    else:
                        execfile(self._configuration_filename)
                except:
                    raise RuntimeError("Failed to load WW PH configuration file="
                                       +self._configuration_filename)
            else:
                raise RuntimeError("***WW PH Extension: The configuration file "
                                   +self._configuration_filename+" either does "
                                   "not exist or cannot be read")
        else:
            print("WW PH Extension: No user-specified configuration file "
                  "supplied - using defaults")

        # process any suffix and/or annotation data, if they exists.
        self.process_suffix_file(ph)
        self.process_annotation_file(ph)

        # set up the mip gap for iteration 0.
        if self.Iteration0MipGap > 0.0:
            print("WW PH Extension: Setting mipgap to %.7f, as specified in "
                  "the configuration file" % self.Iteration0MipGap)
            ph._mipgap = self.Iteration0MipGap

        # search for the presence of the normalized-term-diff converger 
        # (first priority) or the standard term-diff converger (second priority).
        self.converger_to_use = None
        for converger in ph._convergers:
            if converger._name == "normalized-term-diff":
                self.converger_to_use = converger
                break
            elif converger._name == "term-diff":
                self.converger_to_use = converger
                break
        if self.converger_to_use == None:
            raise RuntimeError("WW PH extension plugin failed to locate a normalized term-diff or term-diff converger on the PH object")

#==================================================
    def post_iteration_0_solves(self, ph):

        self._collect_variable_bounds(ph)

        # Collect suffix dictionaries that we will check inside the
        # next loop
        Iter0FixIfConvergedAtLB = self._suffixes['Iter0FixIfConvergedAtLB']
        Iter0FixIfConvergedAtUB = self._suffixes['Iter0FixIfConvergedAtUB']
        Iter0FixIfConvergedAtNB = self._suffixes['Iter0FixIfConvergedAtNB']
        CostForRho = self._suffixes['CostForRho']

        for stage, tree_node, variable_id, variable_values, is_fixed, is_stale in \
              scenario_tree_node_variables_generator_noinstances(
                  ph._scenario_tree,
                  includeDerivedVariables=False,
                  includeLastStage=False):

            if (is_stale is False):
                """ preSEP is not a good idea; E[W] will not be 0
                if (self.ComputeRhosWithpreSEP) and (variable_id in CostForRho):
                    # Watson and Woodruff Comp. Mgt. Sci. 
                    # right before the SEP expressions: a per-scenario rho

                    node_average = tree_node._averages[variable_id]
                    for scenario in tree_node._scenarios:
                        var_value = scenario._x[tree_node._name][variable_id]
                        # dlw: not sure that max(.,1) is the right thing...
                        rhoval = CostForRho[variable_id] * self.RhosSEPMult / max(math.fabs(var_value - node_average), 1)
                        if self.Verbose or ph._verbose:
                            print ("wwphextension is setting rho to %f for scenario=%s, variable id=%s" % (rhoval, str(scenario) , str(variable_id))) 
                    ph.setRhoOneScenario(
                        tree_node,
                        scenario,
                        variable_id,
                        rhoval)
                """
                if (self.ComputeRhosWithSEP) and (variable_id in CostForRho):

                    node_average = tree_node._averages[variable_id]
                    deviation_from_average = 0.0
                    sumprob = 0.0
                    for scenario in tree_node._scenarios:
                        scenario_probability = scenario._probability
                        var_value = scenario._x[tree_node._name][variable_id]
                        deviation_from_average += \
                            (scenario_probability * \
                             math.fabs(var_value - node_average))
                        sumprob += scenario_probability
                    # expected deviation
                    deviation_from_average /= sumprob

                    node_min = \
                        self.Int_If_Close_Enough(ph,
                                                 tree_node._minimums[variable_id])
                    node_max = \
                        self.Int_If_Close_Enough(ph,
                                                 tree_node._maximums[variable_id])

                    if tree_node.is_variable_discrete(variable_id):
                        denominator = max(node_max - node_min + 1, 1)
                    else:
                        denominator = max(deviation_from_average, 1)

                    # CostForRho are the costs to be used as the
                    # numerator in the rho computation below.
                    if self.Verbose or ph._verbose:
                        print ("wwphextension is setting rho to %f for variable id=%s" % (CostForRho[variable_id] * self.RhosSEPMult / denominator , str(variable_id))) 
                    ph.setRhoAllScenarios(
                        tree_node,
                        variable_id,
                        CostForRho[variable_id] * self.RhosSEPMult / denominator)
                
                if is_fixed is False:

                    if tree_node.is_variable_discrete(variable_id):
                        node_min = \
                            self.Int_If_Close_Enough(
                                ph,
                                tree_node._minimums[variable_id])
                        node_max = \
                            self.Int_If_Close_Enough(
                                ph,
                                tree_node._maximums[variable_id])

                        # update convergence prior to checking for fixing.
                        self._int_convergence_tracking(ph,
                                                       tree_node,
                                                       variable_id,
                                                       node_min,
                                                       node_max)
                                    
                        lb = self.Iter0FixIfConvergedAtLB
                        if variable_id in Iter0FixIfConvergedAtLB:
                            lb = Iter0FixIfConvergedAtLB[variable_id]

                        ub = self.Iter0FixIfConvergedAtUB
                        if variable_id in Iter0FixIfConvergedAtUB:
                            ub = Iter0FixIfConvergedAtUB[variable_id]

                        nb = self.Iter0FixIfConvergedAtNB
                        if variable_id in Iter0FixIfConvergedAtNB:
                            nb = Iter0FixIfConvergedAtNB[variable_id]

                        if self._should_fix_discrete_due_to_conv(tree_node,
                                                                 variable_id,
                                                                 lb,
                                                                 ub,
                                                                 nb):
                            self._fix_var(ph, tree_node, variable_id, node_min)
                        elif self.W_hash_history_len > 0:
                            # if not fixed, then hash - no slamming at iteration 0

                            # obviously not checking for cycles at iteration 0!
                            self._w_history_accounting(ph, tree_node, variable_id)

                    else:

                        node_min = tree_node._minimums[variable_id]
                        node_max = tree_node._maximums[variable_id]

                        self._continuous_convergence_tracking(ph,
                                                              tree_node,
                                                              variable_id,
                                                              node_min,
                                                              node_max)

# jpw: not sure if we care about cycle detection in continuous variables?
#                           if self.W_hash_history_len > 0:
#                              self._w_history_accounting(ph, tree_node, variable_id)


#==================================================
    def post_iteration_0(self, ph):

        pass

#==================================================

    def pre_iteration_k_solves(self, ph):

        # NOTE: iteration 0 mipgaps are handled during extension
        # initialization, following PH initialization.

        if (self.InitialMipGap > 0 and self.FinalMipGap >= 0) and \
           self.InitialMipGap > self.FinalMipGap:

            if ph._current_iteration == 1:
                print("WW PH Extension: Setting mipgap to %.7f, as "
                      "specified in the configuration file" % self.InitialMipGap)
                ph._mipgap = self.InitialMipGap

            else:

                m0 = self.converger_to_use._metric_history[0]
                m1 = self.converger_to_use._metric_history[1]
                m = self.converger_to_use.lastMetric()
                mlast = self.converger_to_use._convergence_threshold

                basis_value = m0
                if self.StartMipGapFromIter0Metric == False:
                    basis_value = m1

                x = 1.0 - (m-mlast)/(basis_value-mlast)
                y = 1.0 - x**self.MipGapExponent

                g0 = self.InitialMipGap
                glast = self.FinalMipGap

                new_gap = y * (g0-glast) + glast

                if new_gap > g0:
                    print("WW PH Extension: ***CAUTION - setting mipgap to "
                          "thresholded maximal initial value=%.7f; "
                          "unthresholded value=%.7f" % (g0, new_gap))
                    new_gap = g0
                else:
                    print("WW PH Extension: Setting mipgap to %.7f, based "
                          "on current value of the convergence metric"
                          % (new_gap))
                ph._mipgap = new_gap

#==================================================
    def post_iteration_k_solves(self, ph):

        # Collect suffix dictionaries that we will check inside the
        # next loop
        FixWhenItersConvergedAtLB = self._suffixes['FixWhenItersConvergedAtLB']
        FixWhenItersConvergedAtUB = self._suffixes['FixWhenItersConvergedAtUB']
        FixWhenItersConvergedAtNB = self._suffixes['FixWhenItersConvergedAtNB']

        # track all variables for which cycles have been detected -
        # other plugins may want to react to / report on this
        # information.
        self.variables_with_detected_cycles = [] # consists of tuples of variable id, name, cycle length, cycle message, and tree node
        self.variable_fixed = False

        print ("WW PH Extension: Analyzing variables for fixing")

        for stage, tree_node, variable_id, variable_values, is_fixed, is_stale in \
              scenario_tree_node_variables_generator_noinstances(
                  ph._scenario_tree,
                  includeDerivedVariables=False,
                  includeLastStage=False):

            # if the variable is stale, don't waste time fixing and
            # cycle checking. for one, the code will crash :-) due to
            # None values observed during the cycle checking
            # computation.
            if (is_stale is False) and (is_fixed is False):

                variable_name, index = tree_node._variable_ids[variable_id]
                full_variable_name = variable_name+indexToString(index)
                if tree_node.is_variable_discrete(variable_id):
                    node_min = \
                        self.Int_If_Close_Enough(ph,
                                                 tree_node._minimums[variable_id])
                    node_max = \
                        self.Int_If_Close_Enough(ph,
                                                 tree_node._maximums[variable_id])

                    # update convergence prior to checking for fixing.
                    self._int_convergence_tracking(ph,
                                                   tree_node,
                                                   variable_id,
                                                   node_min,
                                                   node_max)

                    lb = self.FixWhenItersConvergedAtLB
                    if variable_id in FixWhenItersConvergedAtLB:
                        lb = FixWhenItersConvergedAtLB[variable_id]

                    ub = self.FixWhenItersConvergedAtUB
                    if variable_id in FixWhenItersConvergedAtUB:
                        ub = FixWhenItersConvergedAtUB[variable_id]

                    nb = self.FixWhenItersConvergedAtNB
                    if variable_id in FixWhenItersConvergedAtNB:
                        nb = FixWhenItersConvergedAtNB[variable_id]

                    if self._should_fix_discrete_due_to_conv(tree_node,
                                                             variable_id,
                                                             lb,
                                                             ub,
                                                             nb):
                            
                        self._fix_var(ph, tree_node, variable_id, node_min)
                        
                    else:

                        # check to see if a cycle exists for this variable,
                        # and record it if it does - cycle breaking will
                        # happen later, if it happens at all.
                        if self.W_hash_history_len > 0:

                            self._w_history_accounting(ph, tree_node, variable_id)

                            computed_cycle_length, msg = \
                                self.compute_cycle_length(ph,
                                                          tree_node,
                                                          variable_id,
                                                          False)

                            if computed_cycle_length > 0:
                                if (computed_cycle_length >= self.CycleLengthSlamThreshold) or \
                                        self.ReportPotentialCycles:
                                    self.variables_with_detected_cycles.append(
                                        (variable_id, full_variable_name, 
                                         computed_cycle_length, msg, tree_node))

                else:

                    # obviously don't round in the continuous case.
                    node_min = tree_node._minimums[variable_id]
                    node_max = tree_node._maximums[variable_id]

                    # update w statistics for whatever nefarious
                    # purposes are enabled.
                    if self.W_hash_history_len > 0:
                        self._w_history_accounting(ph,
                                                   tree_node,
                                                   variable_id)

                        # update convergence prior to checking for
                        # fixing.
                        self._continuous_convergence_tracking(ph,
                                                              tree_node,
                                                              variable_id,
                                                              node_min,
                                                              node_max)

                    if self._should_fix_continuous_due_to_conv(tree_node,
                                                               variable_id):
                        # fixing to max value for safety (could only
                        # be an issue due to tolerances).
                        self._fix_var(ph, tree_node, variable_id, node_max)
                        # note: we currently don't slam continuous variables!

        # while cycles could be broken by variable fixing, the
        # notions of cycle breaking and variable fixing are really
        # independent. in particular, cycles is indicative of bad
        # rhos and/or xbar estimates, indicating the weights 
        # probably need to be adjusted in any case.
        if len(self.variables_with_detected_cycles) > 0:
            print ("WW PH Extension: Cycles were detected - initiating cycle analysis and remediation")
            if self.Verbose or ph._verbose:
                    print ("WW PH Extension: Cycle information:")
                    print ("Variable            Cycle Length     Cycle Details")
            for variable_id, full_variable_name, computed_cycle_length, cycle_msg, tree_node in self.variables_with_detected_cycles:
                if self.Verbose or ph._verbose:
                    print ("%20s %4d         %s" % (full_variable_name, computed_cycle_length, cycle_msg))
                if (computed_cycle_length \
                       >= self.CycleLengthSlamThreshold) and \
                       ((ph._current_iteration - self._last_slam_iter) \
                             > self.PH_Iters_Between_Cycle_Slams):
                    # TBD: we may not want to slam
                    # immediately - it may disappear on
                    # its own after a few iterations,
                    # depending on what other variables do.
                    # note: we are *not* slamming the
                    # offending variable, but a selected variable
                    if self.Verbose or ph._verbose:
                        print(cycle_msg)
                        print("        Cycle length exceeds iteration slamming "
                              "threshold="
                              +str(self.CycleLengthSlamThreshold)+
                              "; choosing a variable to slam")
                        
                        self._pick_one_and_slam_it(ph)
                        self._reset_w_reduce_rho(ph,
                                                 tree_node,
                                                 variable_id,
                                                 full_variable_name)
                    elif (computed_cycle_length > 1) and \
                            (computed_cycle_length \
                                 < self.CycleLengthSlamThreshold):
                        # there was a (potential) cycle, but
                        # the slam threshold wasn't reached.
                        if (self.Verbose or ph._verbose):
                            print(cycle_msg)
                            print("    Taking no action to break cycle - "
                                  "length="+str(computed_cycle_length)+
                                  " does not exceed slam threshold="
                                  +str(self.CycleLengthSlamThreshold))
                    elif (computed_cycle_length \
                              >= self.CycleLengthSlamThreshold) and \
                              ((ph._current_iteration - self._last_slam_iter) \
                                   > self.PH_Iters_Between_Cycle_Slams):
                        # we could have slammed, but we
                        # recently did and are taking a break
                        # to see if things settle down on
                        # their own.
                        if self.Verbose or ph._verbose:
                            print(cycle_msg)
                            print("    Taking no action to break cycle - "
                                  "length="+str(computed_cycle_length)+
                                  " does exceed slam threshold="
                                  +str(self.CycleLengthSlamThreshold)+
                                  ", but another variable was slammed "
                                  "within the past "
                                  +str(self.PH_Iters_Between_Cycle_Slams)+
                                  " iterations")

        #######

        if (ph._current_iteration > self.SlamAfterIter) and \
           ((ph._current_iteration - self._last_slam_iter) \
            > self.PH_Iters_Between_Cycle_Slams):

            if (self.SlamOnlyIfNotConverging and not self.converger_to_use.isImproving(self.PH_Iters_Between_Cycle_Slams)) or \
                    (not self.SlamOnlyIfNotConverging):
                print("Slamming criteria are satisifed - accelerating convergence")
                self._pick_one_and_slam_it(ph)
                self._just_slammed_ = True
            else:
                self._just_slammed_ = False                
        else:
            self._just_slammed_ = False

        ### THIS IS EXPERIMENTAL - CODE MAY BELONG SOMEWHERE ELSE ###
        for stage, tree_node, variable_id, variable_values, is_fixed, is_stale in \
              scenario_tree_node_variables_generator_noinstances(
                  ph._scenario_tree,
                  includeDerivedVariables=False,
                  includeLastStage=False):

            last_flip_iter = tree_node._w_last_sign_flip_iter[variable_id]
            flip_duration = ph._current_iteration - last_flip_iter

            if (self.CheckWeightOscillationAfterIter > 0) and \
               (ph._current_iteration >= self.CheckWeightOscillationAfterIter):
                if (last_flip_iter is 0) or \
                   (flip_duration >= self.FixIfWeightOscillationCycleLessThan):
                    pass
                else:
                    if self._slam(ph, tree_node, variable_id) is True:
                        tree_node._w_last_sign_flip_iter[variable_id] = 0 
                        return            

#==================================================
    def post_iteration_k(self, ph):

        pass

#==================================================
    def post_ph_execution(self, ph):

        if self.fix_converged_discrete_variables_at_exit is True:
            print("WW PH extension: Fixing all discrete variables that "
                  "are converged at termination")
            self._fix_all_converged_discrete_variables(ph)

#=========================
    def Int_If_Close_Enough(self, ph, x):
        # if x is close enough to the nearest integer, return the integer
        # else return x
        if abs(round(x)-x) <= ph._integer_tolerance:
            return int(round(x))
        else:
            return x

#=========================
    def _int_convergence_tracking(self,
                                  ph,
                                  tree_node,
                                  variable_id,
                                  node_min,
                                  node_max):
        
        # keep track of cumulative iters of convergence to the same int
        if (node_min == node_max) and (type(node_min) is int):
            if node_min == tree_node._last_converged_val[variable_id]:
                tree_node._num_iters_converged[variable_id] += 1
            else:
                tree_node._num_iters_converged[variable_id] = 1
                tree_node._last_converged_val[variable_id] = node_min
        else:
            tree_node._num_iters_converged[variable_id] = 0
            tree_node._last_converged_val[variable_id] = 0.5

#=========================
    def _continuous_convergence_tracking(self,
                                         ph,
                                         tree_node,
                                         variable_id,
                                         node_min,
                                         node_max):
        # keep track of cumulative iters of convergence to the same
        # value within tolerance.
        if abs(node_max - node_min) <= ph._integer_tolerance:
            if abs(node_min - tree_node._last_converged_val[variable_id]) \
               <= ph._integer_tolerance:
                tree_node._num_iters_converged[variable_id] = \
                    tree_node._num_iters_converged[variable_id] + 1
            else:
                tree_node._num_iters_converged[variable_id] = 1
                tree_node._last_converged_val[variable_id] = node_min
        else:
            tree_node._num_iters_converged[variable_id] = 0
            # TBD - avoid the magic constant!
            tree_node._last_converged_val[variable_id] = 0.2342343243223423

#=========================
    def _w_history_accounting(self, ph, tree_node, variable_id):
        # do the w hash accounting work
        # we hash on the variable ph weights, and not the values; the
        # latter may not shift for some time, while the former should.
        self.W_hash_rand_val = self.W_hash_seed

        new_sign_vector = []
        old_sign_vector = tree_node._w_sign_vector[variable_id]

        for scenario in tree_node._scenarios:
            weight_value = scenario._w[tree_node._name][variable_id]
            weight_sign = True
            if weight_value < 0.0:
                weight_sign = False
            tree_node._w_hash[variable_id,ph._current_iteration] += \
                weight_value * self.W_hash_rand_val

            new_sign_vector.append(weight_sign)
            self.W_hash_rand_val = \
                (self.W_hash_b + self.W_hash_a * self.W_hash_rand_val) \
                % self.W_hash_c

        hash_val = tree_node._w_hash[variable_id,ph._current_iteration]

        num_flips = 0
        for i in xrange(0,len(old_sign_vector)):
            if new_sign_vector[i] != old_sign_vector[i]:
                num_flips += 1

        tree_node._w_sign_vector[variable_id] = new_sign_vector

        if num_flips >= 1:
            tree_node._w_last_sign_flip_iter[variable_id] = ph._current_iteration

    def compute_cycle_length(self,
                             ph,
                             tree_node,
                             variable_id,
                             report_possible_cycles):

        # return cycles back to closest hash hit for hashval or 0 if
        # no hash hit

        # if the values are converged, then don't report a cycle -
        # often, the weights at convergence are 0s, and even if they
        # aren't, they won't move if the values are uniform.
        if (tree_node._num_iters_converged[variable_id] == 0) and \
           (variable_id not in tree_node._fixed):
            current_hash_value = None
            current_hash_value = \
                tree_node._w_hash[variable_id,ph._current_iteration]
            # scan starting from the farthest point back in history to
            # the closest - this is required to identify the longest
            # possible cycles, which is what we want.
            for i in xrange(max(ph._current_iteration-self.W_hash_history_len-1,1),
                            ph._current_iteration - 1, 1):
                this_hash_value = tree_node._w_hash[variable_id,i]
                if current_hash_value == 0.0: 
                    relative_diff = float("inf")
                else:
                    relative_diff = math.fabs(this_hash_value - current_hash_value) / math.fabs(current_hash_value) * 100.0
                # we compare w hash values relatively, as opposed to absolutely.
                if relative_diff <= self.WHashComparisonTolerance:
                    if report_possible_cycles is True:
                        variable_name, index = tree_node._variable_ids[variable_id]
                        print("        Possible cycle detected via PH weight hashing - "
                              "variable="+variable_name+indexToString(index)+
                              " node="+ tree_node._name)
                    msg = ("        Current hash value="+str(current_hash_value)+
                           " matched (within tolerance) hash value="
                           +str(this_hash_value)+" found at PH iteration="
                           +str(i)+"; cycle length="
                           +str(ph._current_iteration - i))

                    if self.ReportCycleWHashDetail:
                        variable_name, index = tree_node._variable_ids[variable_id]
                        print("Cycle W hash history detail for variable="+variable_name+indexToString(index))
                        print("Current hash value: %f" % current_hash_value)
                        print("Iteration  Hash Value   % Diff. Relative to Current Hash Value")
                        for j in xrange(max(ph._current_iteration-self.W_hash_history_len-1,1),
                                        ph._current_iteration - 1, 1):
                            iteration_j_hash_value = tree_node._w_hash[variable_id,j]
                            relative_diff = math.fabs(iteration_j_hash_value - current_hash_value)/math.fabs(current_hash_value)
                            print("%4d %16.6f %10.4f" % (j, iteration_j_hash_value, relative_diff*100.0))
                    return ph._current_iteration - i, msg
        return 0, ""

    def _fix_var(self, ph, tree_node, variable_id, fix_value):

        # fix the variable, account for it and maybe output some trace
        # information
        # note: whether you fix at current values or not can severly
        # impact feasibility later in the game. my original thought
        # was below - but that didn't work out. if you make integers,
        # well, integers, all appears to be well.
        # IMPT: we are leaving the values for individual variables
        #       alone, at potentially smallish and heterogeneous
        #       values. if we fix/round, we run the risk of
        #       infeasibilities due to numerical issues. the computed
        #       value below is strictly for output purposes.
        #       dlw note:
        #       as of aug 1 '09, node_min and node_max should be int
        #       if they should be (so to speak)

        variable_name, index = tree_node._variable_ids[variable_id]
        if self.Verbose or ph._verbose:
            print("        Fixing variable="+variable_name+indexToString(index)+
                  " at tree node="+tree_node._name+" to value="
                  +str(fix_value)+"; converged for "
                  +str(tree_node._num_iters_converged[variable_id])+
                  " iterations")

        tree_node.fix_variable(variable_id, fix_value)

        if tree_node.is_variable_discrete(variable_id):
            self.cumulative_discrete_fixed_count += 1
        else:
            self.cumulative_continuous_fixed_count += 1

        # set the global state flag indicator
        self.variable_fixed = True

    # the last 3 input arguments are the number of iterations the
    # variable is required to be at the respective bound (or lack
    # thereof) before fixing can be initiated.
    def _should_fix_discrete_due_to_conv(self,
                                         tree_node,
                                         variable_id,
                                         lb_iters,
                                         ub_iters,
                                         nb_iters):
        # return True if this should be fixed due to convergence

        # jpw: i don't think this logic is correct - shouldn't
        #   "non-bound" be moved after the lb/ub checks - this doesn't
        #   check a bound!
        # dlw reply: i meant it to mean "without regard to bound" so i
        #   have updated the document
        if nb_iters > 0 and tree_node._num_iters_converged[variable_id] >= nb_iters:
            return True
        else:
            # there is a possibility that the variable doesn't have a
            # bound specified, in which case we should obviously
            # ignore the corresponding lb_iters/ub_iters/nb_iters -
            # which
            # should be none as well!
            (lb, ub) = tree_node._variable_bounds[variable_id]
            conval = tree_node._last_converged_val[variable_id]
            # note: if they are converged node_max == node_min
            if (lb is not None) and (lb_iters > 0) and \
               (tree_node._num_iters_converged[variable_id] >= lb_iters) and \
               (conval == lb):
                return True
            elif (ub is not None) and (ub_iters > 0) and \
                 (tree_node._num_iters_converged[variable_id] >= ub_iters) and \
                 (conval == ub):
                return True
        # if we are still here, nothing triggered fixing
        return False

#=========================
    def _should_fix_continuous_due_to_conv(self, tree_node, variable_id):

        if self.fix_continuous_variables:
            if (self.FixWhenItersConvergedContinuous > 0) and \
               (tree_node._num_iters_converged[variable_id] \
                >= self.FixWhenItersConvergedContinuous):

                return True

        # if we are still here, nothing triggered fixing
        return False

#=========================
    def _slam(self, ph, tree_node, variable_id):
        # this function returns a boolean indicating if it slammed
        # TBD: in the distant future: also: slam it to somewhere it
        #      sort of wants to go
        # e.g., the anywhere case could be to the mode or if more than
        #   one dest is True, pick the one closest to the average as
        #   of sept 09, it is written with the implicit assumption
        #   that only one destination is True or that if not, then
        #   min/max trumps lb/ub and anywhere trumps all

        variable_name, index = tree_node._variable_ids[variable_id]
        lb, ub = tree_node._variable_bounds[variable_id]

        if tree_node.is_variable_discrete(variable_id):
            node_min = \
                self.Int_If_Close_Enough(
                    ph,
                    tree_node._minimums[variable_id])
            node_max = \
                self.Int_If_Close_Enough(
                    ph,
                    tree_node._maximums[variable_id])
            anywhere = round(tree_node._averages[variable_id])
        else:
            node_min = tree_node._minimums[variable_id]
            node_max = tree_node._maximums[variable_id]
            anywhere = tree_node._averages[variable_id]

        slam_basis_string = ""
        fix_value = None
        if self._suffixes['CanSlamToLB'].get(variable_id,
                                             self.CanSlamToLB):
            fix_value = lb
            slam_basis_string = "lower bound"
        if self._suffixes['CanSlamToMin'].get(variable_id,
                                              self.CanSlamToMin):
            fix_value = node_min
            slam_basis_string = "node minimum"
        if self._suffixes['CanSlamToUB'].get(variable_id,
                                             self.CanSlamToUB):
            fix_value = ub
            slam_basis_string = "upper bound"
        if self._suffixes['CanSlamToMax'].get(variable_id,
                                              self.CanSlamToMax):
            fix_value = node_max
            slam_basis_string = "node maximum"
        if self._suffixes['CanSlamToAnywhere'].get(variable_id,
                                                   self.CanSlamToAnywhere):
            fix_value = anywhere
            slam_basis_string = "node average (anywhere)"
        if fix_value is None:
            print("        Warning: Not allowed to slam variable="
                  +variable_name+indexToString(index)+" at tree node="
                  +tree_node._name)
            return False
        else:
            print("        Slamming variable="+variable_name+indexToString(index)+
                  " at tree node="+tree_node._name+" to value="
                  +str(fix_value)+"; value="+slam_basis_string)
            self._fix_var(ph, tree_node, variable_id, fix_value)
            return True

#=========================
    def _pick_one_and_slam_it(self, ph):

        my_stage_suffix = self._variable_stage

        for variable_id in self.slam_list:

            # did we find at least one node to slam in?
            didone = False;

            # it is possible (even likely) that the slam list contains
            # variable values that reside in the final stage - which,
            # because of the initialization loops in the
            # post_ph_initialization() method, will not have a _stage
            # attribute defined.  check for the presence of this
            # attribute and skip if not present, as it doesn't make
            # sense to slam variable values in the final stage anyway.
            if variable_id in my_stage_suffix:
                variable_stage = my_stage_suffix[variable_id]
                for tree_node in variable_stage._tree_nodes:
                    # Find the correct tree node
                    if variable_id in tree_node._variable_ids:
                        # determine if the variable is already fixed (the
                        # trusting version...).
                        if not tree_node.is_variable_fixed(variable_id):
                            didone = self._slam(ph, tree_node, variable_id)
                        break
                if didone:
                    self._last_slam_iter = ph._current_iteration
                    return

        if self.Verbose or ph._verbose:
            print("        Warning: Nothing free with a non-zero slam priority - "
                  "no variable will be slammed")

        # DLW says: Hey, look at this: if we were to start deleting
        # from the slam list this would be wrong."
        if len(self.slam_list) == 0:
            if self.Verbose or ph._verbose:
                print("        (No Slamming Priorities were specified in "
                      "a suffix file.)")

    def _reset_w_reduce_rho(self, ph, tree_node, variable_id, variable_name):

        # only output the rho reduction information if the rho factor
        # will actually have an impact (i.e., it is non-unity).
        if self.Verbose or ph._verbose:
            print("        Resetting W for variable="+variable_name+" to zero"),
            if self.RhoReductionFactor != 1.0:
                print (" and multiplying rho by the RhoReductionFactor="
                  +str(self.RhoReductionFactor)),

        # reset w to zero and reduce rho
        average_rho_value = 0.0
        for scenario in tree_node._scenarios:
            scenario._w[tree_node._name][variable_id] = 0.0
            scenario._rho[tree_node._name][variable_id] *= self.RhoReductionFactor
            average_rho_value += scenario._rho[tree_node._name][variable_id]
        average_rho_value /= float(len(tree_node._scenarios))
        if self.Verbose or ph._verbose:
            if self.RhoReductionFactor != 1.0:
                print("- new average (across all scenarios) rho value="+str(average_rho_value)),

        if self.ScenarioRhoPerturbation != 0.0:
            if self.Verbose or ph._verbose:            
                print("; perturbing rho per-scenario")
            lb = 1.0 - self.ScenarioRhoPerturbation
            ub = 1.0 + self.ScenarioRhoPerturbation
            for scenario in tree_node._scenarios:        
                scenario._rho[tree_node._name][variable_id] *= random.uniform(lb,ub)
        
        if self.Verbose or ph._verbose:
            print("")

    # a simple utility to fix any discrete variables to their common
    # value, assuming they are at a common value
    def _fix_all_converged_discrete_variables(self, ph):

        num_variables_fixed = 0

        for stage, tree_node, variable_id, variable_values, is_fixed, is_stale in \
              scenario_tree_node_variables_generator_noinstances(
                  ph._scenario_tree,
                  includeDerivedVariables=False,
                  includeLastStage=False):

            # if the variable is stale, don't waste time fixing and
            # cycle checking. for one, the code will crash :-) due to
            # None values observed during the cycle checking
            # computation.
            if (is_stale is False) and (is_fixed is False):

                if tree_node.is_variable_discrete(variable_id):
                    node_min = \
                        self.Int_If_Close_Enough(ph,
                                                 tree_node._minimums[variable_id])
                    node_max = \
                        self.Int_If_Close_Enough(ph,
                                                 tree_node._maximums[variable_id])

                    if node_min == node_max:
                        self._fix_var(ph, tree_node, variable_id, node_min)
                        num_variables_fixed += 1

        print("WW PH Extension: Total number of variables fixed at PH termination "
              "due to convergence="+str(num_variables_fixed))
