/usr/bin/powernap_calculator is in powernap 2.21-0ubuntu1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
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#
# powernap_calculator - estimate power savings using statistcal analysis
# Copyright (C) 2009 Canonical Ltd.
#
# Authors: Dustin Kirkland <kirkland@canonical.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 3 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import getopt
import sys
# command line options
short_opts = 'h:p:g:'
long_opts = ['hosts=', 'guests-per-host=', 'guests=']
usage_string = "Usage:\n powernap_calculator [-h|--hosts NUM] [-p|--guests-per-host NUM] [-g|--guests NUM]"
if len(sys.argv) != 7:
print(usage_string)
exit(1)
# parse getopt options
try:
opts, args = getopt.getopt(sys.argv[1:], short_opts, long_opts)
for k, v in opts:
if k in ('-h', '--hosts'):
hosts = int(v)
elif k in ('-p', '--guests-per-host'):
guests_per_host = int(v)
elif k in ('-g', '--guests'):
guests = int(v)
else:
print(usage_string)
exit(1)
except:
print(usage_string)
exit(1)
# convert an input num to a different base with each
# digit as an element in the list;
# ensure that the sum of the digits equals the number of guests;
# return the list representing the way vm's are allocated across hosts
def vm_allocations(num, base, hosts, guests):
list = [0]*hosts
i = 0
while num != 0:
remainder = num % base
list[i] = remainder
i += 1
num = num / base
if sum(list) == guests:
return list
else:
return -1
# count the number of zero's found in the list
def count_zeros(list):
count = 0
for i in list:
if i == 0:
count += 1
return count
print("Calculating...\n ")
# this might be a *very* big number
upper_limit = (guests_per_host+1)**hosts
zeros = [0]*(hosts + 1)
total = 0
num = 0
# brute force all possible combinations
while num < upper_limit:
# determine the associated vm_allocations for this particular index
list = vm_allocations(num, guests_per_host+1, hosts, guests)
if list != -1:
# count the zeros in this list
c = count_zeros(list)
zeros[c] += 1
total += 1
# print a helpful running percent-done
if num % 100000 == 0:
print("\b\b\b\b\b\b\b\b\b\b%.3f%% " % (100.*num/upper_limit))
num += 1
print("\nIn a cloud with [%d] hosts, which can handle [%d] guests-per-host, currently running [%d] guests,\nyou may expect the following:\n" % (hosts, guests_per_host, guests))
expected_savings = 0
#print zeros
# do the calculations
for i in range(0, len(zeros)):
if zeros[i] > 0:
probability = 1. * zeros[i] / total
if probability > 0 and probability < .01:
pstr = "<1"
else:
pstr = "%.1f" % (100. * probability)
savings = 100.*i/hosts
print("[%5s%%] likely that [%d/%d] of your hosts would powernap, for a [%.0f%%] power savings" % (pstr, i, hosts, savings))
expected_savings += probability * savings
print("\nThe overall expected value is [%.1f%%] power savings." % expected_savings)
exit(0)
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