def __init__(self, include, require=None, exclude=None, subquery=None, position_cutoff=None):
     self.include = OrderedSet(include)
     self.require = require or OrderedSet()
     self.exclude = exclude or OrderedSet()
     self.subquery = subquery or {}
     self.position_cutoff = position_cutoff
     if isinstance(self.require, (list, tuple)):
         self.require = OrderedSet(self.require)
     if isinstance(self.exclude, (list, tuple)):
         self.exclude = OrderedSet(self.exclude)

    def on_attach(self, fgraph):
        """
        When attaching to a new fgraph, check that
            1) This DestroyHandler wasn't already attached to some fgraph
               (its data structures are only set up to serve one)
            2) The FunctionGraph doesn't already have a DestroyHandler.
               This would result in it validating everything twice, causing
               compilation to be slower.

        Give the FunctionGraph instance:
            1) A new method "destroyers(var)"
                TODO: what does this do exactly?
            2) A new attribute, "destroy_handler"
        TODO: WRITEME: what does this do besides the checks?
        """

        ####### Do the checking ###########
        already_there = False
        if self.fgraph is fgraph:
            already_there = True
        if self.fgraph is not None:
            raise Exception("A DestroyHandler instance can only serve one" " FunctionGraph. (Matthew 6:24)")
        for attr in ("destroyers", "destroy_handler"):
            if hasattr(fgraph, attr):
                already_there = True

        if already_there:
            # FunctionGraph.attach_feature catches AlreadyThere and cancels the attachment
            raise toolbox.AlreadyThere(
                "DestroyHandler feature is already present" " or in conflict with another plugin."
            )

        ####### Annotate the FunctionGraph ############

        def get_destroyers_of(r):
            droot, impact, root_destroyer = self.refresh_droot_impact()
            try:
                return [root_destroyer[droot[r]]]
            except Exception:
                return []

        fgraph.destroyers = get_destroyers_of
        fgraph.destroy_handler = self

        self.fgraph = fgraph
        self.destroyers = OrderedSet()  # set of Apply instances with non-null destroy_map
        self.view_i = OrderedDict()  # variable -> variable used in calculation
        self.view_o = OrderedDict()  # variable -> set of variables that use this one as a direct input
        # clients: how many times does an apply use a given variable
        self.clients = OrderedDict()  # variable -> apply -> ninputs
        self.stale_droot = True

        self.debug_all_apps = OrderedSet()
        if self.do_imports_on_attach:
            toolbox.Bookkeeper.on_attach(self, fgraph)

class Query(object):
    """

    Parameters
    ----------
    position_cutoff : float
        Used by SequenceDB to keep only optimizer that are positioned before
        the cut_off point.

    """

    def __init__(self, include, require=None, exclude=None,
                 subquery=None, position_cutoff=None):
        self.include = OrderedSet(include)
        self.require = require or OrderedSet()
        self.exclude = exclude or OrderedSet()
        self.subquery = subquery or {}
        self.position_cutoff = position_cutoff
        if isinstance(self.require, (list, tuple)):
            self.require = OrderedSet(self.require)
        if isinstance(self.exclude, (list, tuple)):
            self.exclude = OrderedSet(self.exclude)

    def __str__(self):
        return ("Query{inc=%s,ex=%s,require=%s,subquery=%s,"
                "position_cutoff=%d}" %
                (self.include, self.exclude, self.require, self.subquery,
                 self.position_cutoff))

    # add all opt with this tag
    def including(self, *tags):
        return Query(self.include.union(tags),
                     self.require,
                     self.exclude,
                     self.subquery,
                     self.position_cutoff)

    # remove all opt with this tag
    def excluding(self, *tags):
        return Query(self.include,
                     self.require,
                     self.exclude.union(tags),
                     self.subquery,
                     self.position_cutoff)

    # keep only opt with this tag.
    def requiring(self, *tags):
        return Query(self.include,
                     self.require.union(tags),
                     self.exclude,
                     self.subquery,
                     self.position_cutoff)

 def __init__(
     self, include, require=None, exclude=None, subquery=None, position_cutoff=float("inf"), extra_optimizations=None
 ):
     self.include = OrderedSet(include)
     self.require = require or OrderedSet()
     self.exclude = exclude or OrderedSet()
     self.subquery = subquery or {}
     self.position_cutoff = position_cutoff
     if extra_optimizations is None:
         extra_optimizations = []
     self.extra_optimizations = extra_optimizations
     if isinstance(self.require, (list, tuple)):
         self.require = OrderedSet(self.require)
     if isinstance(self.exclude, (list, tuple)):
         self.exclude = OrderedSet(self.exclude)

 def __init__(self, include, require=None, exclude=None,
              subquery=None, position_cutoff=None):
     """
     :type position_cutoff: float
     :param position_cutoff: Used by SequenceDB to keep only optimizer that
                             are positioned before the cut_off point.
     """
     self.include = OrderedSet(include)
     self.require = require or OrderedSet()
     self.exclude = exclude or OrderedSet()
     self.subquery = subquery or {}
     self.position_cutoff = position_cutoff
     if isinstance(self.require, (list, tuple)):
         self.require = OrderedSet(self.require)
     if isinstance(self.exclude, (list, tuple)):
         self.exclude = OrderedSet(self.exclude)

        def on_attach(self, fgraph):
            """
            When attaching to a new fgraph, check that
            1) This DestroyHandler wasn't already attached to some fgraph
               (its data structures are only set up to serve one)
            2) The FunctionGraph doesn't already have a DestroyHandler.
               This would result in it validating everything twice, causing
               compilation to be slower.

            TODO: WRITEME: what does this do besides the checks?
            """

            ####### Do the checking ###########
            already_there = False
            if self.fgraph is fgraph:
                already_there = True
            if self.fgraph not in [None, fgraph]:
                raise Exception("A DestroyHandler instance can only serve"
                                " one FunctionGraph. (Matthew 6:24)")
            for attr in ('destroyers', 'destroy_handler'):
                if hasattr(fgraph, attr):
                    already_there = True

            if already_there:
                # FunctionGraph.attach_feature catches AlreadyThere
                # and cancels the attachment
                raise toolbox.AlreadyThere(
                    "DestroyHandler feature is already present or in"
                    " conflict with another plugin.")

            ####### end of checking ############

            def get_destroyers_of(r):
                droot, impact, root_destroyer = self.refresh_droot_impact()
                try:
                    return [root_destroyer[droot[r]]]
                except Exception:
                    return []

            fgraph.destroyers = get_destroyers_of
            fgraph.destroy_handler = self

            self.fgraph = fgraph
            self.destroyers = OrderedSet() #set of Apply instances with non-null destroy_map
            self.view_i = {}  # variable -> variable used in calculation
            self.view_o = {}  # variable -> set of variables that use this one as a direct input
            #clients: how many times does an apply use a given variable
            self.clients = {} # variable -> apply -> ninputs
            self.stale_droot = True

            # IG: It's unclear if this is meant to be included in deployed code. It looks like
            # it is unnecessary if FunctionGraph is working correctly, so I am commenting uses
            # of it (for speed) but leaving the commented code in place so it is easy to restore
            # for debugging purposes.
            # Note: is there anything like the C preprocessor for python? It would be useful to
            # just ifdef these things out
            # self.debug_all_apps = set()
            if self.do_imports_on_attach:
                toolbox.Bookkeeper.on_attach(self, fgraph)

def _build_droot_impact(destroy_handler):
    droot = {}   # destroyed view + nonview variables -> foundation
    impact = {}  # destroyed nonview variable -> it + all views of it
    root_destroyer = {}  # root -> destroyer apply

    for app in destroy_handler.destroyers:
        for output_idx, input_idx_list in app.op.destroy_map.items():
            if len(input_idx_list) != 1:
                raise NotImplementedError()
            input_idx = input_idx_list[0]
            input = app.inputs[input_idx]

            # Find non-view variable which is ultimatly viewed by input.
            view_i = destroy_handler.view_i
            _r = input
            while _r is not None:
                r = _r
                _r = view_i.get(r)
            input_root = r

            if input_root in droot:
                raise InconsistencyError(
                    "Multiple destroyers of %s" % input_root)
            droot[input_root] = input_root
            root_destroyer[input_root] = app

            # The code here add all the variables that are views of r into
            # an OrderedSet input_impact
            input_impact = OrderedSet()

            q = deque()
            q.append(input_root)
            while len(q) > 0:
                v = q.popleft()
                for n in destroy_handler.view_o.get(v, []):
                    input_impact.add(n)
                    q.append(n)

            for v in input_impact:
                assert v not in droot
                droot[v] = input_root

            impact[input_root] = input_impact
            impact[input_root].add(input_root)

    return droot, impact, root_destroyer

    def __query__(self, q):
        if not isinstance(q, Query):
            raise TypeError('Expected a Query.', q)
        # The ordered set is needed for deterministic optimization.
        variables = OrderedSet()
        for tag in q.include:
            variables.update(self.__db__[tag])
        for tag in q.require:
            variables.intersection_update(self.__db__[tag])
        for tag in q.exclude:
            variables.difference_update(self.__db__[tag])
        remove = OrderedSet()
        add = OrderedSet()
        for obj in variables:
            if isinstance(obj, DB):
                def_sub_query = q
                if q.extra_optimizations:
                    def_sub_query = copy.copy(q)
                    def_sub_query.extra_optimizations = []
                sq = q.subquery.get(obj.name, def_sub_query)

                replacement = obj.query(sq)
                replacement.name = obj.name
                remove.add(obj)
                add.add(replacement)
        variables.difference_update(remove)
        variables.update(add)
        return variables

class Query(object):
    """

    Parameters
    ----------
    position_cutoff : float
        Used by SequenceDB to keep only optimizer that are positioned before
        the cut_off point.

    """

    def __init__(self, include, require=None, exclude=None,
                 subquery=None, position_cutoff=None,
                 extra_optimizations=None):
        self.include = OrderedSet(include)
        self.require = require or OrderedSet()
        self.exclude = exclude or OrderedSet()
        self.subquery = subquery or {}
        self.position_cutoff = position_cutoff
        if extra_optimizations is None:
            extra_optimizations = []
        self.extra_optimizations = extra_optimizations
        if isinstance(self.require, (list, tuple)):
            self.require = OrderedSet(self.require)
        if isinstance(self.exclude, (list, tuple)):
            self.exclude = OrderedSet(self.exclude)

    def __str__(self):
        return ("Query{inc=%s,ex=%s,require=%s,subquery=%s,"
                "position_cutoff=%d,extra_opts=%s}" %
                (self.include, self.exclude, self.require, self.subquery,
                 self.position_cutoff, self.extra_optimizations))

    def __setstate__(self, state):
        self.__dict__.update(state)
        if not hasattr(self, 'extra_optimizations'):
            self.extra_optimizations = []

    # add all opt with this tag
    def including(self, *tags):
        return Query(self.include.union(tags),
                     self.require,
                     self.exclude,
                     self.subquery,
                     self.position_cutoff,
                     self.extra_optimizations)

    # remove all opt with this tag
    def excluding(self, *tags):
        return Query(self.include,
                     self.require,
                     self.exclude.union(tags),
                     self.subquery,
                     self.position_cutoff,
                     self.extra_optimizations)

    # keep only opt with this tag.
    def requiring(self, *tags):
        return Query(self.include,
                     self.require.union(tags),
                     self.exclude,
                     self.subquery,
                     self.position_cutoff,
                     self.extra_optimizations)

    def register(self, *optimizations):
        return Query(self.include,
                     self.require,
                     self.exclude,
                     self.subquery,
                     self.position_cutoff,
                     self.extra_optimizations + list(optimizations))

    def orderings(self, fgraph):
        """Return orderings induced by destructive operations.

        Raise InconsistencyError when
        a) attempting to destroy indestructable variable, or
        b) attempting to destroy a value multiple times, or
        c) an Apply destroys (illegally) one of its own inputs by aliasing

        """
        rval = OrderedDict()

        if self.destroyers:
            # BUILD DATA STRUCTURES
            # CHECK for multiple destructions during construction of variables

            droot, impact, __ignore = self.refresh_droot_impact()

            # check for destruction of constants
            illegal_destroy = [r for r in droot if
                               getattr(r.tag, 'indestructible', False) or
                               isinstance(r, graph.Constant)]
            if illegal_destroy:
                raise InconsistencyError(
                    "Attempting to destroy indestructible variables: %s" %
                    illegal_destroy)

            # add destroyed variable clients as computational dependencies
            for app in self.destroyers:
                # for each destroyed input...
                for output_idx, input_idx_list in iteritems(app.op.destroy_map):
                    destroyed_idx = input_idx_list[0]
                    destroyed_variable = app.inputs[destroyed_idx]
                    root = droot[destroyed_variable]
                    root_impact = impact[root]
                    # we generally want to put all clients of things which depend on root
                    # as pre-requisites of app.
                    # But, app is itself one such client!
                    # App will always be a client of the node we're destroying
                    # (destroyed_variable, but the tricky thing is when it is also a client of
                    # *another variable* viewing on the root.  Generally this is illegal, (e.g.,
                    # add_inplace(x, x.T).  In some special cases though, the in-place op will
                    # actually be able to work properly with multiple destroyed inputs (e.g,
                    # add_inplace(x, x).  An Op that can still work in this case should declare
                    # so via the 'destroyhandler_tolerate_same' attribute or
                    # 'destroyhandler_tolerate_aliased' attribute.
                    #
                    # destroyhandler_tolerate_same should be a list of pairs of the form
                    # [(idx0, idx1), (idx0, idx2), ...]
                    # The first element of each pair is the input index of a destroyed
                    # variable.
                    # The second element of each pair is the index of a different input where
                    # we will permit exactly the same variable to appear.
                    # For example, add_inplace.tolerate_same might be [(0,1)] if the destroyed
                    # input is also allowed to appear as the second argument.
                    #
                    # destroyhandler_tolerate_aliased is the same sort of list of
                    # pairs.
                    # op.destroyhandler_tolerate_aliased = [(idx0, idx1)] tells the
                    # destroyhandler to IGNORE an aliasing between a destroyed
                    # input idx0 and another input idx1.
                    # This is generally a bad idea, but it is safe in some
                    # cases, such as
                    # - the op reads from the aliased idx1 before modifying idx0
                    # - the idx0 and idx1 are guaranteed not to overlap (e.g.
                    #   they are pointed at different rows of a matrix).
                    #

                    # CHECK FOR INPUT ALIASING
                    # OPT: pre-compute this on import
                    tolerate_same = getattr(app.op,
                                            'destroyhandler_tolerate_same', [])
                    assert isinstance(tolerate_same, list)
                    tolerated = OrderedSet(idx1 for idx0, idx1 in tolerate_same
                                           if idx0 == destroyed_idx)
                    tolerated.add(destroyed_idx)
                    tolerate_aliased = getattr(
                        app.op, 'destroyhandler_tolerate_aliased', [])
                    assert isinstance(tolerate_aliased, list)
                    ignored = OrderedSet(idx1 for idx0, idx1 in tolerate_aliased
                                         if idx0 == destroyed_idx)
                    # print 'tolerated', tolerated
                    # print 'ignored', ignored
                    for i, input in enumerate(app.inputs):
                        if i in ignored:
                            continue
                        if input in root_impact \
                                and (i not in tolerated or
                                     input is not destroyed_variable):
                            raise InconsistencyError("Input aliasing: %s (%i, %i)"
                                                     % (app, destroyed_idx, i))

                    # add the rule: app must be preceded by all other Apply instances that
                    # depend on destroyed_input
                    root_clients = OrderedSet()
                    for r in root_impact:
                        assert not [a for a, c in self.clients[r].items() if not c]
                        root_clients.update([a for a, c in self.clients[r].items() if c])
                    root_clients.remove(app)
                    if root_clients:
                        rval[app] = root_clients
#.........这里部分代码省略.........

#.........这里部分代码省略.........
               This would result in it validating everything twice, causing
               compilation to be slower.

        Give the FunctionGraph instance:
            1) A new method "destroyers(var)"
                TODO: what does this do exactly?
            2) A new attribute, "destroy_handler"
        TODO: WRITEME: what does this do besides the checks?
        """

        # Do the checking #
        already_there = False
        if self.fgraph is fgraph:
            already_there = True
        if self.fgraph is not None:
            raise Exception(
                "A DestroyHandler instance can only serve one"
                " FunctionGraph. (Matthew 6:24)")
        for attr in ('destroyers', 'destroy_handler'):
            if hasattr(fgraph, attr):
                already_there = True

        if already_there:
            # FunctionGraph.attach_feature catches AlreadyThere and cancels the attachment
            raise toolbox.AlreadyThere(
                "DestroyHandler feature is already present"
                " or in conflict with another plugin.")

        # Annotate the FunctionGraph #
        self.unpickle(fgraph)
        fgraph.destroy_handler = self

        self.fgraph = fgraph
        self.destroyers = OrderedSet()  # set of Apply instances with non-null destroy_map
        self.view_i = OrderedDict()  # variable -> variable used in calculation
        self.view_o = OrderedDict()  # variable -> set of variables that use this one as a direct input
        # clients: how many times does an apply use a given variable
        self.clients = OrderedDict()  # variable -> apply -> ninputs
        self.stale_droot = True

        self.debug_all_apps = OrderedSet()
        if self.do_imports_on_attach:
            toolbox.Bookkeeper.on_attach(self, fgraph)

    def unpickle(self, fgraph):
        def get_destroyers_of(r):
            droot, impact, root_destroyer = self.refresh_droot_impact()
            try:
                return [root_destroyer[droot[r]]]
            except Exception:
                return []
        fgraph.destroyers = get_destroyers_of

    def refresh_droot_impact(self):
        """
        Makes sure self.droot, self.impact, and self.root_destroyer are
        up to date, and returns them.
        (see docstrings for these properties above)
        """
        if self.stale_droot:
            droot = OrderedDict()   # destroyed view + nonview variables -> foundation
            impact = OrderedDict()  # destroyed nonview variable -> it + all views of it
            root_destroyer = OrderedDict()  # root -> destroyer apply

            for app in self.destroyers:
                for output_idx, input_idx_list in iteritems(app.op.destroy_map):