class BranchPredictor:
def __init__(self, argv):
self.cold_misses = 0
self.num_branches = 0
self.btb_hit_count = 0
self.num_of_btb_entries = 1
self.file_name = 'BranchHistory.txt'
self.parseCommandLineArgs(argv)
self.history_file = file(self.file_name, 'r')
self.findCommonBranch(self.history_file)
self.trace_file = file(self.file_name, 'r')
self.btb = BranchTargetBuffer(self.num_of_btb_entries)
self.local_history_table = [0 for i in xrange(4)]
self.predictors = [0 for i in xrange(4)]
self.correct_prediction = 0
def resetStatCounts (self) :
self.cold_misses = 0
self.num_branches = 0
self.btb_hit_count = 0
self.correct_prediction = 0
def findCommonBranch(self, history_file):
addresses_dict = dict()
for line in self.history_file:
pc_address = line.split()[0]
if pc_address not in addresses_dict:
addresses_dict[pc_address] = 0
else:
addresses_dict[pc_address] += 1
self.common_branch = sorted(addresses_dict, key=addresses_dict.get, reverse=True)[0]
def simulate(self) :
addresses_dict = dict()
self.common_branch_count = 0
self.common_branch_correct_count = 0
for line in self.trace_file:
self.num_branches += 1
split_line = line.split()
if split_line[0] == self.common_branch:
self.common_branch_count += 1
pc_address = int(split_line[0], 16)
branch_address = int(split_line[1], 16)
# Check for BTB cold misses
if pc_address not in addresses_dict:
addresses_dict[pc_address] = branch_address
self.cold_misses += 1
btb_hit, branch_address = self.btb.lookup(pc_address)
if not btb_hit:
branch_address = int(split_line[1], 16)
else:
self.btb_hit_count += 1
# Prediction code
# Look in the history table, from that value
# go to the predictor corresponding to that value.
LHT_index = pc_address%4
predictor_index = self.local_history_table[LHT_index]
taken = self.predictors[predictor_index]
if int(split_line[2]) == taken:
self.correct_prediction += 1
if split_line[0] == self.common_branch:
self.common_branch_correct_count += 1
else :
pass
self.local_history_table[LHT_index] = (predictor_index*2 + int(split_line[2]))%4
self.predictors[predictor_index] = int(split_line[2])
def printStats(self):
template = """\
a. BTB hit rate : %f
b. Misprediction rate : %f
c. Common Branch : %s
Common Branch contribution : %f out of %f
d. Conflict misses : %d
e. Correct predictions : %d"""
values = (float (self.btb_hit_count) / self.num_branches,
1 - float (self.correct_prediction) / self.num_branches,
self.common_branch,
float (self.common_branch_count) / self.num_branches,
float (self.correct_prediction) / self.num_branches,
self.btb.conflict_misses,
self.correct_prediction)
print template % values
def parseCommandLineArgs(self, argv):
try:
opts, args = getopt.getopt(argv, 'e:f:')
except getopt.GetoptError:
help_message()
sys.exit(2)
file_found = False
for opt, arg in opts:
if opt in ("-e"):
self.num_of_btb_entries = int(arg)
elif opt in ('-f'):
self.file_name = arg
file_found = True
else:
help_message()
sys.exit()
if file_found is False:
help_message()
sys.exit()
