From:

~~~ Subject:

On Tue, 13 Feb 1996, michael reid wrote:

jerry bryan was counting (and storing) positions close to start

on magnetic tape. he gave figures for positions within 7 face

turns on july 19, 1994 and positions within 11 quarter turns on

february 4, 1995. (jerry, how many reels of tape did this take?)

It was a little better than 100 tapes. It was roughly 20GB of data. I

stored 14 bytes per position (could have done it in 13 bytes, but I stored

the lengths with each permutation). Each "position" was really a

representative of an equivalence class of M-conjugates (usually)

containing 48 elements. Hence, it took about 14/48 bytes (about 2.33

bits) to store each position. This isn't too shabby, but it is nowhere as

compact as the coding scheme discussed in the "How Big is Big?" thread.

the diameter isn't known. the best lower bounds are 20 face turns,

or 24 quarter turns, both from considering the position "superflip".

the best upper bounds are 29 face turns, or 42 quarter turns.

A 24q process is known for superflip. It is known that superflip is

greater than 19f. Is a 20f process known for superflip?

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Robert G. Bryan (Jerry Bryan) jbryan@pstcc.cc.tn.us Pellissippi State (423) 539-7127 10915 Hardin Valley Road (423) 694-6435 (fax) P.O. Box 22990 Knoxville, TN 37933-0990