1 files changed, 110 insertions, 0 deletions

diff --git a/src/consensus/consensus-simulation.py.in b/src/consensus/consensus-simulation.py.in
new file mode 100644
index 000000000..6629ffaa8
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+++ b/src/consensus/consensus-simulation.py.in
@@ -0,0 +1,110 @@
+#!@PYTHON@
+# This file is part of GNUnet
+# (C) 2013, 2018 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., 51 Franklin Street, Fifth Floor,
+# Boston, MA 02110-1301, USA.
+
+from __future__ import absolute_import
+from __future__ import print_function
+import argparse
+import random
+from math import ceil, log, floor
+from past.builtins import xrange
+
+
+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)
+    # py2-3 compatible, backwards.
+    # refer to http://python-future.org/compatible_idioms.html#xrange
+    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)