From mreid@ptc.com Wed Feb 22 18:14:54 1995 Return-Path: Received: from ptc.com (poster.ptc.com) by life.ai.mit.edu (4.1/AI-4.10) for /com/archive/cube-lovers id AA12024; Wed, 22 Feb 95 18:14:54 EST Received: from ducie by ptc.com (5.0/SMI-SVR4-NN) id AA17114; Wed, 22 Feb 95 18:13:15 EST Received: by ducie (1.38.193.4/sendmail.28-May-87) id AA22074; Wed, 22 Feb 1995 18:28:13 -0500 Date: Wed, 22 Feb 1995 18:28:13 -0500 From: mreid@ptc.com (michael reid) Message-Id: <9502222328.AA22074@ducie> To: bryan@wvnvm.wvnet.edu, cube-lovers@ai.mit.edu Subject: Re: Run Times, Storage Requirements, etc. Content-Length: 1698 jerry writes about his search for superflip in 22q: > [ ... ] However, I had to spread the > runs over a couple of weeks to keep our operators from shooting me. isn't it amazing how they never seem to fully understand the importance of this stuff! :-) > Finally, the 82 tapes for positions 11 moves from Superflip were > matched against the 82 tapes for positions 11 moves from Start, again > taking about 10 hours. (I also checked the shorter lengths along the > way, but it didn't take anywhere near as long for the shorter lengths). i think this can be done much more efficiently. well, at least if you set things up properly in the first place. suppose that you use an order (for sorting positions) in which the corner configuration is more significant than the edge configuration. then, for each position X on your huge list, you need to check if repr(X superflip) is on the list. since superflip only affects edges, the corner configuration of X superflip is the same as that of X. thus the same holds for repr(X superflip) and repr(X) = X. therefore, you only need to look for repr(X superflip) nearby in the sorted list. now, for each corner configuration, load all the positions on your list with that corner configuration into memory (it shouldn't be too many), superflip them, compute representative elements, and look for "halfway" positions. this way, there's no need to sort or store all the positions 11q from superflip (although it wouldn't be hard using this). of course this also works for pons asinorum and its composition with superflip. but it does require that things were set up properly in the beginning. mike