This may be of interest to some of the ex-Lifers on Math-Fun. --Rich ----- Forwarded message from LifeCA@yahoogroups.com ----- Date: Fri, 13 Jun 2014 19:37:28 -0700 From: "Mark Niemiec mniemiec@gmail.com [LifeCA]" Subject: [LifeCA] Life still-life syntheses complete up to 17 bits To: LifeCA mailing list <LifeCA@yahoogroups.com> Back in the 1980s and 1990s, Dave Buckingham completed the monumental task of synthesizing all stable and repeating Life objects up to 14 bits, including over a thousand still-lifes. When I put up my Life synthesis web site in the late 1990s (initially based largely on his work), I had planned to extend this to the 15-bit still-lifes. Most of these appeared to have fairly obvious syntheses, but there were around half a dozen that for which syntheses did not seem at all obvious. By around 2001, I had reduced this down to three objects without syntheses. Around 2002, I wrote an expert system that attempts to find syntheses for given lists of objects, by using a brute-force search through a library of synthesis recipes (currently numbering over 800 recipes). By filtering out 9)%+ of trivial objects, this allows one to concentrate on the few difficult and interesting remaining objects. This was able to find explicit syntheses for all 15-bit still-lifes except twelve, for which I already had syntheses for all but the "hard three", which formally confirmed what I had already deduced informally. This list remained unchanged for almost a decade; I was finally able to solve one in 2011. Last year, I discovered the conwaylife.com forums, and mentioned the unsolved still-lifes. With a great deal of help from Martin Grant (aka extrementhusiast), we were able to finish the remaining two 15-bit still-lifes in September and October. This success spurred interest into the unsolved 16-bit still-lifes, of which there were slightly under a hundred. Martin, Matthias Merzenich and myself (which some additional help of a few others) were able to solve most of these by the end of the year, with the last few being solved in the first week of January. This momentum continued to the 396 unsolved 17-bit still-lifes, which which were finally completed on May 17 of this year. <clip --Rich> ------------------------------------ Posted by: Mark Niemiec <mniemiec@gmail.com> ------------------------------------ <*> To visit your group on the web, go to: http://groups.yahoo.com/group/LifeCA/ ----- End forwarded message -----