def ite_build(bdd):
"""
Implementation of the efficient 'ite' method of building a BDD
discussed in Bryan et al's paper "Efficient Implementation of a
BDD Package"
"""
ite.ite_build(bdd)
def _walk_variable_up(num_nodes, current_position, bdd, out, verbose):
best_order = bdd["var_order"]
#walk var to top
while(current_position > 0):
_reset_bdd(bdd)
tmp = bdd["var_order"][current_position-1]
bdd["var_order"][current_position-1] = bdd["var_order"][current_position]
bdd["var_order"][current_position] = tmp
current_position -= 1
ite.ite_build(bdd)
if num_nodes > bdd["u"]+1:
num_nodes = bdd["u"]+1
best_order = list(bdd["var_order"])
if verbose:
print "Walk Up New Number of Nodes: %d" % num_nodes
print "Walk Up New Var Order: %s" % str(bdd["var_order"])
out["num_nodes"] = num_nodes
out["best_order"] = best_order
def _walk_variable_up(num_nodes, current_position, bdd, out, verbose):
best_order = bdd["var_order"]
#walk var to top
while (current_position > 0):
_reset_bdd(bdd)
tmp = bdd["var_order"][current_position - 1]
bdd["var_order"][current_position -
1] = bdd["var_order"][current_position]
bdd["var_order"][current_position] = tmp
current_position -= 1
ite.ite_build(bdd)
if num_nodes > bdd["u"] + 1:
num_nodes = bdd["u"] + 1
best_order = list(bdd["var_order"])
if verbose:
print("Walk Up New Number of Nodes: %d" % num_nodes)
print("Walk Up New Var Order: %s" % str(bdd["var_order"]))
out["num_nodes"] = num_nodes
out["best_order"] = best_order
def reorder_ite_build(bdd, vars_to_consider=[], verbose=False):
"""
Parameters:
bdd - the bdd to build and minimize
vars_to_consider - the list of varibles to reorder
verbose - whether info should be printed during build time
"""
ite.ite_build(bdd)
num_nodes = bdd["u"]+1
num_vars = len(bdd["var_order"])
if verbose:
print "Original Number of Nodes: %d" % num_nodes
print "Number of Variables: %d" % num_vars
checked_vars = {}
if not vars_to_consider:
vars_to_consider = bdd["var_order"]
for v in vars_to_consider:
checked_vars[v] = False
while False in checked_vars.values():
var_to_be_checked = None
for key in checked_vars:
if not checked_vars[key]:
var_to_be_checked = key
break
best_order = list(bdd["var_order"])
original_order = best_order
current_position = bdd["var_order"].index(var_to_be_checked)
if verbose:
print "Current Variable: %s" % var_to_be_checked
original_position = current_position
#start thread to walk to top
walk_up_bdd = copy.deepcopy(bdd)
walk_up_out = {"num_nodes":None, "best_order":None}
walk_up_thread = threading.Thread(
target=_walk_variable_up,
args=(copy.copy(num_nodes),
copy.copy(current_position),
walk_up_bdd,
walk_up_out,
verbose)
)
walk_up_thread.start()
#walk var to bottom
for j in range(original_position,num_vars):
_reset_bdd(bdd) #reset our bdd to try again
tmp = bdd["var_order"][j]
bdd["var_order"][j] = bdd["var_order"][current_position]
bdd["var_order"][current_position] = tmp
current_position = j
ite.ite_build(bdd)
if num_nodes > bdd["u"]+1:
num_nodes = bdd["u"]+1
best_order = list(bdd["var_order"])
if verbose:
print "Walk Down New Number of Nodes: %d" % num_nodes
print "Walk Down New Var Order: %s" % str(bdd["var_order"])
walk_up_thread.join()
if num_nodes > walk_up_out["num_nodes"]:
num_nodes = walk_up_out["num_nodes"]
best_order = walk_up_out["best_order"]
#mark var as checked
checked_vars[var_to_be_checked] = True
bdd["var_order"] = best_order
_reset_bdd(bdd)
bdd["var_order"] = best_order
ite.ite_build(bdd)
if verbose:
print "Final Number of Nodes: %d" % num_nodes
print "Final Var Order %s" % str(bdd["var_order"])
def ite_build(bdd):
ite.ite_build(bdd)
def reorder_ite_build(bdd, vars_to_consider=[], verbose=False):
"""
Parameters:
bdd - the bdd to build and minimize
vars_to_consider - the list of varibles to reorder
verbose - whether info should be printed during build time
"""
ite.ite_build(bdd)
num_nodes = bdd["u"] + 1
num_vars = len(bdd["var_order"])
if verbose:
print("Original Number of Nodes: %d" % num_nodes)
print("Number of Variables: %d" % num_vars)
checked_vars = {}
if not vars_to_consider:
vars_to_consider = bdd["var_order"]
for v in vars_to_consider:
checked_vars[v] = False
while False in checked_vars.values():
var_to_be_checked = None
for key in checked_vars:
if not checked_vars[key]:
var_to_be_checked = key
break
best_order = list(bdd["var_order"])
original_order = best_order
current_position = bdd["var_order"].index(var_to_be_checked)
if verbose:
print("Current Variable: %s" % var_to_be_checked)
original_position = current_position
#start thread to walk to top
walk_up_bdd = copy.deepcopy(bdd)
walk_up_out = {"num_nodes": None, "best_order": None}
walk_up_thread = threading.Thread(target=_walk_variable_up,
args=(copy.copy(num_nodes),
copy.copy(current_position),
walk_up_bdd, walk_up_out,
verbose))
walk_up_thread.start()
#walk var to bottom
for j in range(original_position, num_vars):
_reset_bdd(bdd) #reset our bdd to try again
tmp = bdd["var_order"][j]
bdd["var_order"][j] = bdd["var_order"][current_position]
bdd["var_order"][current_position] = tmp
current_position = j
ite.ite_build(bdd)
if num_nodes > bdd["u"] + 1:
num_nodes = bdd["u"] + 1
best_order = list(bdd["var_order"])
if verbose:
print("Walk Down New Number of Nodes: %d" % num_nodes)
print("Walk Down New Var Order: %s" %
str(bdd["var_order"]))
walk_up_thread.join()
if num_nodes > walk_up_out["num_nodes"]:
num_nodes = walk_up_out["num_nodes"]
best_order = walk_up_out["best_order"]
#mark var as checked
checked_vars[var_to_be_checked] = True
bdd["var_order"] = best_order
_reset_bdd(bdd)
bdd["var_order"] = best_order
ite.ite_build(bdd)
if verbose:
print("Final Number of Nodes: %d" % num_nodes)
print("Final Var Order %s" % str(bdd["var_order"]))
def ite_build(bdd):
ite.ite_build(bdd)