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+#!/usr/bin/python
+# This file is part of GNUnet
+# (C) 2013 Christian Grothoff (and other contributing authors)
+#
+# GNUnet 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; either version 2, or (at your
+# option) any later version.
+#
+# GNUnet 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 GNUnet; see the file COPYING. If not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+
+import argparse
+import random
+from math import ceil,log,floor
+
+def bsc(n):
+ """ count the bits set in n"""
+ l = n.bit_length()
+ c = 0
+ x = 1
+ for _ in range(0, l):
+ if n & x:
+ c = c + 1
+ x = x << 1
+ return c
+
+def simulate(k, n, verbose):
+ assert k < n
+ largest_arc = int(2**ceil(log(n, 2))) / 2
+ num_ghosts = (2 * largest_arc) - n
+ if verbose:
+ print "we have", num_ghosts, "ghost peers"
+ # n.b. all peers with idx<k are evil
+ peers = range(n)
+ info = [1 << x for x in xrange(n)]
+ def done_p():
+ for x in xrange(k, n):
+ if bsc(info[x]) < n-k:
+ return False
+ return True
+ rounds = 0
+ while not done_p():
+ if verbose:
+ print "-- round --"
+ arc = 1
+ while arc <= largest_arc:
+ if verbose:
+ print "-- subround --"
+ new_info = [x for x in info]
+ for peer_physical in xrange(n):
+ peer_logical = peers[peer_physical]
+ peer_type = None
+ partner_logical = (peer_logical + arc) % n
+ partner_physical = peers.index(partner_logical)
+ if peer_physical < k or partner_physical < k:
+ if verbose:
+ print "bad peer in connection", peer_physical, "--", partner_physical
+ continue
+ if peer_logical & arc == 0:
+ # we are outgoing
+ if verbose:
+ print peer_physical, "connects to", partner_physical
+ peer_type = "outgoing"
+ if peer_logical < num_ghosts:
+ # we have a ghost, check if the peer who connects
+ # to our ghost is actually outgoing
+ ghost_partner_logical = (peer_logical - arc) % n
+ if ghost_partner_logical & arc == 0:
+ peer_type = peer_type + ", ghost incoming"
+ new_info[peer_physical] = new_info[peer_physical] | info[peer_physical] | info[partner_physical]
+ new_info[partner_physical] = new_info[partner_physical] | info[peer_physical] | info[partner_physical]
+ else:
+ peer_type = "incoming"
+ if verbose > 1:
+ print "type of", str(peer_physical) + ":", peer_type
+ info = new_info
+ arc = arc << 1;
+ rounds = rounds + 1
+ random.shuffle(peers)
+ return rounds
+
+if __name__ == "__main__":
+ parser = argparse.ArgumentParser()
+ parser.add_argument("k", metavar="k", type=int, help="#(bad peers)")
+ parser.add_argument("n", metavar="n", type=int, help="#(all peers)")
+ parser.add_argument("r", metavar="r", type=int, help="#(rounds)")
+ parser.add_argument('--verbose', '-v', action='count')
+
+ args = parser.parse_args()
+ sum = 0.0;
+ for n in xrange (0, args.r):
+ sum += simulate(args.k, args.n, args.verbose)
+ print sum / args.r;
+
+