def __lv2ibt(segment):
stack = []
has_crit_b = False
if segment.empty():
raise EmptyError(
"An empty Segment cannot be transformed into a BTree")
for i in range(segment.length() - 1, -1, -1):
v = segment[i]
if v.is_leaf():
stack.append(Leaf(v))
elif v.is_critical():
stack.append(Leaf(v))
if has_crit_b:
raise IllFormedError(
"A ill-formed Segment cannot be transformed into a BTree"
)
else:
has_crit_b = True
else:
if len(stack) < 2:
raise IllFormedError(
"A ill-formed Segment cannot be transformed into a BTree"
)
lv = stack.pop()
rv = stack.pop()
stack.append(Node(v, lv, rv))
if len(stack) != 1:
raise IllFormedError(
"A ill-formed Segment cannot be transformed into a BTree")
else:
return has_crit_b, stack[0]
def __node_uacc_local_compute(stack, d, phi, v, psi_l, res, psi_r, i, k):
"""Computes when the value is a node"""
if len(stack) < 2:
raise IllFormedError(
"uacc_local cannot be applied if there is a node that does not have two children "
"in the current instance")
# We get the values of two sub upward accumulation
lv = stack.pop()
rv = stack.pop()
if d == 0:
# The current node is an ancestor of a critical value by the left
# That is, there is a critical value on its left children in a BTree representation
# We process and stack the value of a partial accumulation
val = phi(v.get_value())
stack.append(psi_l(lv, val, rv))
res[i] = None
elif d == 1:
# The current node is an ancestor of a critical value by the left
# That is, there is a critical value on its left children in a BTree representation
# We process and stack the value of a partial accumulation
val = phi(v.get_value())
stack.append(psi_r(lv, val, rv))
res[i] = None
d = 0
else:
# We did not meet a critical value, we can process a normal upward accumulation with k
val = k(lv, v.get_value(), rv)
res[i] = TaggedValue(val, v.get_tag())
stack.append(val)
d = d - 1
return d, stack, res
def dacc_local(self, gl, gr, c):
"""Computes local downward accumulation for the current instance using an
accumulative parameter resulting of a global downward accumulation
Parameters
----------
gl : callable
Function to make a downward accumulation to the left
gr : callable
Function to make a downward accumulation to the right
c
Initial value of the accumulator
Raises
------
IllFormedError:
If the current instance does not represent a correct linearized subtree
That is there are several leaves that doesn't have a parent in a BTree representation
or if there is not a value to accumulate from above
"""
# We update not finished accumulation locally using the value from the parent in the global
# representation of a linearized tree
stack = [c]
res = Segment([None] * self.length())
for i in range(self.length()):
v = self[i]
if v.is_leaf() or v.is_critical():
if len(stack) == 0:
raise IllFormedError(
"dacc_local cannot be applied if there are two leaf values, or critical "
"values that do not have a parent")
# We get the accumulated value passed from the last parent
val = stack.pop()
res[i] = TaggedValue(val, v.get_tag())
else: # v.is_node()
if len(stack) == 0:
raise IllFormedError(
"dacc_local cannot be applied if there is not a value to accumulate from "
"above")
val = stack.pop()
# We get the accumulated value passed from the last parent
# And two new ones, one for the left children, and one to the right, using
# the gr and gl functions
res[i] = TaggedValue(val, v.get_tag())
stack.append(gr(val, v.get_value()))
stack.append(gl(val, v.get_value()))
return res
def uacc_update(self, seg2, k, lc, rc):
"""Makes an update of the current accumulation, using initial values and the top
accumulated values
Precondition
-------------
The lengths of self and seg2 should be equal
Parameters
----------
seg2 : :obj:`Segment`
Result of a local accumulation
k : callable
The function used to reduce a BTree into a single value
lc
Top value of the left children in a global structure
rc
Top value of the left children in a global structure
Raises
------
IllFormedError
If the current instance does not represent a correct linearized subtree
That is there is a node that doesn't have two children
"""
assert self.length() == seg2.length(), "uacc_update cannot needs to " \
"Segment of same size as input"
stack = [rc, lc]
d = MINUS_INFINITY
res = Segment([None] * self.length())
for i in reversed(range(seg2.length())):
v1 = self[i]
v2 = seg2[i]
# We update the accumulation from seg2
# We stack the values already updated to process updates on nodes
if v1.is_leaf():
# The result of the accumulation is the node made in seg2
res[i] = v2
stack.append(v2.get_value())
d = d + 1
elif v1.is_node():
res, stack, d = self.__node_uacc_update_compute(
stack, d, res, k, v1, v2, i)
else: # v1.is_critical()
if len(stack) < 2:
raise IllFormedError(
"uacc_update cannot be applied if there is a node that "
"does not have two children in the current instance")
# We need two sub accumulation values to process the accumulation of a critical node
lv = stack.pop()
rv = stack.pop()
val = k(lv, v1.get_value(), rv)
res[i] = TaggedValue(val, v1.get_tag())
stack.append(val)
d = 0
return res
def __rev_segment_to_trees(lb, glob):
stack = []
for i in range(lb.length() - 1, -1, -1):
if glob[i] == TAG_LEAF:
stack.append(lb[i])
else: # gt[i] == VTag_Node
lbt = stack.pop()
rbt = stack.pop()
stack.append(__graft(lb[i], lbt, rbt))
if len(stack) != 1:
raise IllFormedError(
"A ill-formed list of incomplete BTree cannot be transformed into a BTree"
)
return stack[0]
def dacc_global(self, psi_d, c):
"""Performs sequential downwards accumulation
Precondition
-------------
self should bot have critical nodes
Parameters
----------
psi_d : callable
A function used to respect the closure property on gr and gl (initial functions used for up accumulation)
to make partial downward accumulation
c
Initial value of the accumulator
Raises
------
IllFormedError
If the current instance does not represent a correct linearized subtree
That is there are several leaves that doesn't have a parent in a BTree representation
"""
stack = [c]
res = Segment([None] * self.length())
assert not self.has_critical(
), "dacc_global cannot be applied to Segment which contains a critical node"
for i in range(self.length()):
v = self[i]
if len(stack) == 0:
raise IllFormedError(
"dacc_global cannot be applied to ill-formed Segments that is two leaf values do not have a parent"
)
# We add the previous accumulation as a new value of our result
val = stack.pop()
res[i] = TaggedValue(val, v.get_tag())
# If the current value is node, we need to update the value to pass to the right, and left children
# These values are contained in the stack
if v.is_node():
(to_l, to_r) = v.get_value()
stack.append(psi_d(val, to_r))
stack.append(psi_d(val, to_l))
return res
def uacc_global(self, psi_n):
"""Performs sequential upwards accumulation
Precondition
-------------
self should not have critical nodes
Parameters
----------
psi_n : callable
A function used to respect the closure property on k (the initial function used for accumulation)
to allow partial computation
Raises
------
IllformedError
If the current instance does not represent a correct linearized subtree
That is there is a node that doesn't have two children
"""
assert not self.has_critical(
), "uacc_global cannot be applied to a Segments which contains a critical"
stack = []
res = Segment([None] * self.length())
for i in reversed(range(self.length())):
g = self[i]
# We process a global accumulation using a stack to store previous accumulation,
# to get them for the accumulation on nodes
if g.is_leaf():
res[i] = g
val = g.get_value()
else: # g.is_node()
if len(stack) < 2:
raise IllFormedError(
"uacc_global cannot be applied if there is a node that does not have two children "
"in the current instance")
lv = stack.pop()
rv = stack.pop()
val = psi_n(lv, g.get_value(), rv)
res[i] = TaggedValue(val, g.get_tag())
stack.append(val)
# We get the top value of the accumulation
return res
def reduce_global(self, psi_n):
"""Makes a global reduction using local reductions of Segments
Precondition
-------------
self should empty, and should not have critical nodes
Parameters
----------
psi_n : callable
A function used to respect the closure property on k
(the initial function used for reduction) to allow partial computation
Raises
------
IllFormedError
If the current instance does not represent a list of top values of a correct
list of subtrees
That is for each node, there is not exist two children, of there is a critical
value in the current instance
"""
assert not self.has_critical(), "reduce_global cannot be applied to a" \
"Segments which contains a critical"
assert self != [], "reduce_global cannot be applied to an empty Segment"
stack = []
for g in reversed(self):
# We stack every value we already reduced
if g.is_leaf():
# Nothing to calculate, we only stack the value
stack.append(g.get_value())
else: # g.is_node()
# We get two sub reductions to make a total reduction of the current node
if len(stack) < 2:
raise IllFormedError(
"reduce_global cannot be applied if there is a node that"
"does not have two children in the current instance")
lv = stack.pop()
rv = stack.pop()
# We process and stack a reduction
stack.append(psi_n(lv, g.get_value(), rv))
top = stack.pop()
return top
def __node_uacc_update_compute(stack, d, res, k, v1, v2, i):
"""Computes when the value is a node"""
if len(stack) < 2:
raise IllFormedError(
"uacc_update cannot be applied if there is a node that does not have two children "
"in the current instance")
# We need two sub accumulation values to process the accumulation of a node
lv = stack.pop()
rv = stack.pop()
if d in (0, 1):
# We met a critical value before, so the accumulation is not completed yet
val = k(lv, v1.get_value(), rv)
res[i] = TaggedValue(val, v1.get_tag())
stack.append(val)
d = 0
else:
# We did not meet a critical value before, so the accumulation is completed yet
res[i] = v2
stack.append(v2.get_value())
d = d - 1
return res, stack, d
def __node_reduce_local_compute(stack, d, k, psi_l, phi, v, psi_r):
"""Computes when the value is a node"""
if len(stack) < 2:
raise IllFormedError(
"reduce_local cannot be applied if there is a node that does not have "
"two children in the current instance")
# We get two sub-reductions to make a reduction with the current node value
lv = stack.pop()
rv = stack.pop()
if d == 0:
# The current node is an ancestor of a critical value by the left
# That is, there is a critical value on its left children in a BTree representation
# We process and stack a partial reduction
stack.append(psi_l(lv, phi(v.get_value()), rv))
elif d == 1:
# The current node is an ancestor of a critical value by the right
# That is, there is a critical value on its right children in a BTree representation
# We process and stack a partial reduction
stack.append(psi_r(lv, phi(v.get_value()), rv))
d = 0
else:
# We did not meet a critical value, we process and stack a normal reduction
stack.append(k(lv, v.get_value(), rv))
return stack, d
def uacc_local(self, k, phi, psi_l, psi_r):
"""Computes local upwards accumulation and reduction
Precondition
-------------
self should empty
Parameters
----------
k : callable
The function used to reduce a BTree into a single value
phi : callable
A function used to respect the closure property
psi_l : callable
A function used to respect the closure property to make partial computation on the left
psi_r : callable
A function used to respect the closure property to make partial computation on the right
Raises
------
IllFormedError
If the current instance does not represent a correct linearized subtree
That is there is a node that doesn't have two children which can be either a leaf value or a critical value
"""
assert self != [], "uacc_local cannot be applied to an empty Segment"
stack = []
d = MINUS_INFINITY
res = Segment([None] * self.length())
has_crit = False
for i in reversed(range(self.length())):
v = self[i]
# We stack all the values of previous accumulation
if v.is_leaf():
res[i] = v
stack.append(v.get_value())
d = d + 1
elif v.is_node():
if len(stack) < 2:
raise IllFormedError(
"uacc_local cannot be applied if there is a node that does not have two children "
"in the current instance")
# We get the values of two sub upward accumulation
lv = stack.pop()
rv = stack.pop()
if d == 0:
# The current node is an ancestor of a critical value by the left
# That is, there is a critical value on its left children in a BTree representation
# We process and stack the value of a partial accumulation
val = phi(v.get_value())
stack.append(psi_l(lv, val, rv))
res[i] = None
elif d == 1:
# The current node is an ancestor of a critical value by the left
# That is, there is a critical value on its left children in a BTree representation
# We process and stack the value of a partial accumulation
val = phi(v.get_value())
stack.append(psi_r(lv, val, rv))
res[i] = None
d = 0
else:
# We did not meet a critical value, we can process a normal upward accumulation with k
val = k(lv, v.get_value(), rv)
res[i] = TaggedValue(val, v.get_tag())
stack.append(val)
d = d - 1
else: # v.is_critical()
# The current value is critical. We make a partial accumulation with phi and stack the result
stack.append(phi(v.get_value()))
res[i] = None
d = 0
has_crit = True
top = stack.pop()
tag = "N" if has_crit else "L"
# We return both the top values for following global upward accumulation, and the current accumulated subtree
return TaggedValue(top, tag), res
def reduce_local(self, k, phi, psi_l, psi_r):
"""Reduces a local Segment into a value
Precondition
-------------
self should not be empty
Parameters
----------
k : callable
The function used to reduce a BTree into a single value
phi : callable
A function used to respect the closure property
psi_l : callable
A function used to respect the closure property to make partial computation on the left
psi_r : callable
A function used to respect the closure property to make partial computation on the right
Raises
------
IllFormedError
If the current instance does not represent a correct linearized subtree
That is there is a node that does not have two children which can be either a leaf value or a critical value
"""
assert self != [], "reduce_local cannot be applied to an empty Segment"
stack = []
d = MINUS_INFINITY
has_critical = False
for v in reversed(self):
# Starts by the end, that is the most deep leaves
# We stack every elements we already reduced
if v.is_leaf():
# We cannot reduce a leaf value
stack.append(v.get_value())
d = d + 1
elif v.is_node():
if len(stack) < 2:
raise IllFormedError(
"reduce_local cannot be applied if there is a node that does not have"
"two children in the current instance")
# We get two sub-reductions to make a reduction with the current node value
lv = stack.pop()
rv = stack.pop()
if d == 0:
# The current node is an ancestor of a critical value by the left
# That is, there is a critical value on its left children in a BTree representation
# We process and stack a partial reduction
stack.append(psi_l(lv, phi(v.get_value()), rv))
elif d == 1:
# The current node is an ancestor of a critical value by the right
# That is, there is a critical value on its right children in a BTree representation
# We process and stack a partial reduction
stack.append(psi_r(lv, phi(v.get_value()), rv))
d = 0
else:
# We did not meet a critical value, we process and stack a normal reduction
stack.append(k(lv, v.get_value(), rv))
else: # v.is_critical()
# we process and stack the reduction of critical value
stack.append(phi(v.get_value()))
has_critical = True
d = 0
top = stack.pop()
if has_critical:
# The current instance represented a node in the global structure of a linearized tree
return TaggedValue(top, "N")
else:
# The current instance represented a leaf in the global structure of a linearized tree
return TaggedValue(top, "L")
