Christopher Mowla
Premium Member
Is there an edge flip algorithm less than 25 quarter turn moves?
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Here's an old one with 24:
http://games.groups.yahoo.com/group/speedsolvingrubikscube/message/13700
Nice alg, but that's not what the original post was asking for.Here's an old one with 24:
http://games.groups.yahoo.com/group/speedsolvingrubikscube/message/13700
Maybe it's not what he wanted, but I think it still is a valid answer. At least it definitely is an "odd parity algorithm". The OP was a bit ambiguous, making us guess what exactly he means and even what puzzle he's talking about. Also... do you think he counts R2 as two turns but an inner slice quarter turn as one turn? Seems counter-intuitive to me, so I think with his lower case letters he meant double layer turns rather than inner slice turns, and thus the algs he presented do affect other pieces as well, just like mine. Plus he explicitly mentioned "without messing up the centers" but said nothing about the other edges/corners (except "single edge flip" implies the other edges shouldn't be flipped).Nice alg, but that's not what the original post was asking for.
Nice alg, but that's not what the original post was asking for.Here's an old one with 24:
http://games.groups.yahoo.com/group/speedsolvingrubikscube/message/13700
(Adding R2 U2 R' U2 could qualify, though.)
Maybe it's not what he wanted, but I think it still is a valid answer. At least it definitely is an "odd parity algorithm". The OP was a bit ambiguous, making us guess what exactly he means and even what puzzle he's talking about. Also... do you think he counts R2 as two turns but an inner slice quarter turn as one turn? Seems counter-intuitive to me, so I think with his lower case letters he meant double layer turns rather than inner slice turns, and thus the algs he presented do affect other pieces as well, just like mine. Plus he explicitly mentioned "without messing up the centers" but said nothing about the other edges/corners (except "single edge flip" implies the other edges shouldn't be flipped).Nice alg, but that's not what the original post was asking for.
Dan Cohen said he used ACube to search for all algs in <r,l,U2,B2,D2,F2> and that there were none in fewer than 25 quarter turns. Theoretically there might be a parity alg shorter than that, but I don't think we'll find one with the conventional approach.
EDIT: Lucas's file seems to include "nonpure" algorithms that adjust the last layer by U2, such as the following:
r2 F2 r U2 r U2 x U2 r U2 r' U2 r U2 r2 U2
EDIT: I'm dumb, that was a 25qtm one, but here's a 23:
r' D2 l B2 r' U2 r U2 l' B2 U2 D2 r U2 r'
http://www.speedsolving.com/forum/showthread.php?p=164072#post164072
http://archive.garron.us/paste/text/dp_lrU2F2B2D2.txt
Hence both my OLL parities are 25q. Note what kind of algs you are referring to (Domino).
In fact, I am glad that you answered this post. I wanted to ask you about what you say to be Chris Hardwick's pure edge flip algorithm. Did he really come up with it. I noticed on your site that you ask "how was this found". Has he ever told you? I have always been curious about how, that algorithm was found. I have private messaged Chris and emailed him, but he didn't respond.
Lastly, do you think that there is a way to logically come up with a pure edge flip alg, which is around 25q?
Also, are you certain that every single short algorithm known is not understood by everyone? That's a pretty big assumption.
Chris
Thanks for the 23q alg. for double parity (even though I was seeking the pure one-edge flip). Please tell me, who found this algorithm and how? Did he/she use a computer, trial and error, or logical reasoning?
If that confidence was great, then that person should be able to write 100s of algorithms for the single "edge flip". Obviously all could not be the same length in moves, but, many algorithms should intuitively come out of that person's head (many of them very brief). Furthermore, that person should be able to prove what is the briefest possible algorithm for the one edge "flip" (without tools such as a computer).
What?! Why?From an advanced calculus student's perspective, one who has understood all of the proofs and logic behind the limit, would define a limit much differently than a freshman year calculus student.
Well, many of us easily could.If that confidence was great, then that person should be able to write 100s of algorithms for the single "edge flip".
No. I'm afraid some things in life simply require brute force, and some too much to do by a human.Furthermore, that person should be able to prove what is the briefest possible algorithm for the one edge "flip" (without tools such as a computer).
A computer of course. Did you look at his file? There are hundreds of algorithms there... nobody would waste their time looking for algs like this by hand when computers can do it much faster and guarantee optimality (assuming you entered in the right assumptions).
Well, here's one of length 28 that I just made up:I don't think you would find any good solutions that are not in <r,l,U2,F2,B2,D2>.
Make that a 21:here's a 23:
r' D2 l B2 r' U2 r U2 l' B2 U2 D2 r U2 r'
Well, here's one of length 28 that I just made up:I don't think you would find any good solutions that are not in <r,l,U2,F2,B2,D2>.
Dw' L' U F (r U2 r U2 r U2 r U2 r) F' U' L d L' d' L D L' d L
Ok, so it's a bit longer. But I'm only human.