~kirkland/powernap/trunk : /powernap_calculator (revision 133)

#!/usr/bin/python

#

#    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)