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# Oscar is an OSCillation AnalyzeR for use with Golly.
# Author: Andrew Trevorrow (andrew@trevorrow.com), March 2006.
# Modified to handle B0-and-not-S8 rules, August 2009.
# This script uses Gabriel Nivasch's "keep minima" algorithm.
# For each generation, calculate a hash value for the pattern. Keep all of
# the record-breaking minimal hashes in a list, with the oldest first.
# For example, after 5 generations the saved hash values might be:
#
# 8 12 16 24 25,
#
# If the next hash goes down to 13 then the list can be shortened:
#
# 8 12 13.
#
# When the current hash matches one of the saved hashes, it is highly likely
# the pattern is oscillating. By keeping a corresponding list of generation
# counts we can calculate the period. We also keep lists of population
# counts and bounding boxes; they are used to reduce the chance of spurious
# oscillator detection due to hash collisions. The bounding box info also
# allows us to detect moving oscillators (spaceships/knightships).
import golly as g
from glife import rect, pattern
from time import time
# --------------------------------------------------------------------
# initialize lists
hashlist = [] # for pattern hash values
genlist = [] # corresponding generation counts
poplist = [] # corresponding population counts
boxlist = [] # corresponding bounding boxes
# --------------------------------------------------------------------
def show_spaceship_speed(period, deltax, deltay):
# we found a moving oscillator
if (deltax == deltay) or (deltax == 0) or (deltay == 0):
speed = ""
if (deltax == 0) or (deltay == 0):
# orthogonal spaceship
if (deltax > 1) or (deltay > 1):
speed += str(deltax + deltay)
else:
# diagonal spaceship (deltax == deltay)
if deltax > 1:
speed += str(deltax)
if period == 1:
g.show("Spaceship detected (speed = " + speed + "c)")
else:
g.show("Spaceship detected (speed = " + speed + "c/" +str(period) + ")")
else:
# deltax != deltay and both > 0
speed = str(deltay) + "," + str(deltax)
if period == 1:
g.show("Knightship detected (speed = " + speed + "c)")
else:
g.show("Knightship detected (speed = " + speed + "c/" + str(period) + ")")
# --------------------------------------------------------------------
def oscillating():
# return True if the pattern is empty, stable or oscillating
# first get current pattern's bounding box
prect = g.getrect()
pbox = rect(prect)
if pbox.empty:
g.show("The pattern is empty.")
return True
# get current pattern and create hash of "normalized" version -- ie. shift
# its top left corner to 0,0 -- so we can detect spaceships and knightships
## currpatt = pattern( g.getcells(prect) )
## h = hash( tuple( currpatt(-pbox.left, -pbox.top) ) )
# use Golly's hash command (3 times faster than above code)
h = g.hash(prect)
# check if outer-totalistic rule has B0 but not S8
rule = g.getrule().split(":")[0]
hasB0notS8 = rule.startswith("B0") and (rule.find("/") > 1) and not rule.endswith("8")
# determine where to insert h into hashlist
pos = 0
listlen = len(hashlist)
while pos < listlen:
if h > hashlist[pos]:
pos += 1
elif h < hashlist[pos]:
# shorten lists and append info below
del hashlist[pos : listlen]
del genlist[pos : listlen]
del poplist[pos : listlen]
del boxlist[pos : listlen]
break
else:
# h == hashlist[pos] so pattern is probably oscillating, but just in
# case this is a hash collision we also compare pop count and box size
if (int(g.getpop()) == poplist[pos]) and \
(pbox.wd == boxlist[pos].wd) and \
(pbox.ht == boxlist[pos].ht):
period = int(g.getgen()) - genlist[pos]
if hasB0notS8 and (period % 2 > 0) and (pbox == boxlist[pos]):
# ignore this hash value because B0-and-not-S8 rules are
# emulated by using different rules for odd and even gens,
# so it's possible to have identical patterns at gen G and
# gen G+p if p is odd
return False
if pbox == boxlist[pos]:
# pattern hasn't moved
if period == 1:
g.show("The pattern is stable.")
else:
g.show("Oscillator detected (period = " + str(period) + ")")
else:
deltax = abs(boxlist[pos].x - pbox.x)
deltay = abs(boxlist[pos].y - pbox.y)
show_spaceship_speed(period, deltax, deltay)
return True
else:
# look at next matching hash value or insert if no more
pos += 1
# store hash/gen/pop/box info at same position in various lists
hashlist.insert(pos, h)
genlist.insert(pos, int(g.getgen()))
poplist.insert(pos, int(g.getpop()))
boxlist.insert(pos, pbox)
return False
# --------------------------------------------------------------------
def fit_if_not_visible():
# fit pattern in viewport if not empty and not completely visible
r = rect(g.getrect())
if (not r.empty) and (not r.visible()): g.fit()
# --------------------------------------------------------------------
g.show("Checking for oscillation... (hit escape to abort)")
oldsecs = time()
while not oscillating():
g.run(1)
newsecs = time()
if newsecs - oldsecs >= 1.0: # show pattern every second
oldsecs = newsecs
fit_if_not_visible()
g.update()
fit_if_not_visible()
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