Having analyzed gencols' source code, I concluded, that it uses "spaceship" sensu stricto. I modified the source code so that it traced periodic patterns up to the 20th generation
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--- ../../gencols/output.c 2012-04-15 11:12:57.708179920 +0200
+++ ./output.c 2012-04-15 13:01:04.882425235 +0200
@@ -62,7 +62,7 @@
}
#endif
-#define MAXOSCTEST 4
+#define MAXOSCTEST 20
removefailed=0;
if (countpat(tmp,tgen)
==countpat(pat1gen,tgen)+countpat(pat2gen,tgen)
@@ -157,7 +157,7 @@
if (removefailed && !strchr(filterstring,'f') ) return;
if (per== -1 && !strchr(filterstring,'n') ) return;
if (per>MAXOSCTEST && !strchr(filterstring,'a') ) return;
- if (per>=1 && per <=4 && !strchr(filterstring,'p') &&
+ if (per>=1 && per <= MAXOSCTEST && !strchr(filterstring,'p') &&
!strchr(filterstring,'0'+per)
&& (maxmove!=1 || !strchr(filterstring,'g'))
&& (maxmove!=2 || !strchr(filterstring,'s'))) return;
Then I ran it with
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./gencols -pat obj/puffer2.life obj/allss_e.list -nph 4 -tc 2 21 -gen 21 -genafter 20 -filt p
This way I got 2 widely known versions of Ecologist (one LWSS-based and another MWSS-based) and yet another spaceship with a different spark
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x = 25, y = 18, rule = B3/S23
21b4o$20bo3bo$24bo$20bo2bo2$18b2o$17b5o$10bob3o2bo4bo$8b2o3bo3b3o2bo$
8bobo7bo2b2o$8bob2o7b2o$o8b2o2$11bo2bo$15bo5b4o$11bo3bo4bo3bo$12b4o8bo
$20bo2bo!