From BRYAN@wvnvm.wvnet.edu Fri Jan 20 20:41:10 1995 Return-Path: Received: from WVNVM.WVNET.EDU by life.ai.mit.edu (4.1/AI-4.10) for /com/archive/cube-lovers id AA27138; Fri, 20 Jan 95 20:41:10 EST Message-Id: <9501210141.AA27138@life.ai.mit.edu> Received: from WVNVM.WVNET.EDU by WVNVM.WVNET.EDU (IBM VM SMTP V2R2) with BSMTP id 0675; Fri, 20 Jan 95 17:07:06 EST Received: from WVNVM.WVNET.EDU (NJE origin BRYAN@WVNVM) by WVNVM.WVNET.EDU (LMail V1.2a/1.8a) with BSMTP id 0198; Fri, 20 Jan 1995 17:07:06 -0500 X-Acknowledge-To: Date: Fri, 20 Jan 1995 17:07:05 EST From: "Jerry Bryan" To: , "Cube Lovers List" Subject: Re: superflip in quarter turn metric In-Reply-To: Message of 01/20/95 at 15:58:08 from mreid@ptc.com On 01/20/95 at 15:58:08 mreid@ptc.com said: >i've finished searching for superflip in 20q , and no solutions were >found. thus superflip requires at least 22q , which gives a new lower >bound for the diameter of the cube group in the quarter turn metric. >total cpu spent on the search was 29 cpu hours. based on this, i would >make a rough estimate of 2.5 to 3 months cpu time for an exhaustive >search through depth 22q. Rats. You beat me by about a half hour. I just finished comparing Level 10 of my data base with the same Level 10 superflipped. There were no matches. I just about have Level 11 completed. This will provide interesting new information in and of itself, because previously there has only been an exhaustive search through level 10. Once I complete Level 11, I will superflip it and see what happens. The superflip is especially amenable to a "two half depth search". Normally, you would have to build one tree with Start at the root, and a second tree with X at the root, where X is the position you were testing. But a search tree with superflip at the root is identical to a search tree with Start at the root except that the superflip tree has each element superflipped as compared to the respective element of the tree with Start at the root. Hence, building the tree with Superflip at the root is quite easy once the tree with Start at the root is in hand. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Robert G. Bryan (Jerry Bryan) (304) 293-5192 Associate Director, WVNET (304) 293-5540 fax 837 Chestnut Ridge Road BRYAN@WVNVM Morgantown, WV 26505 BRYAN@WVNVM.WVNET.EDU