From an October 2013 discussion at http://www.speedsolving.com/forum/showthread.php?44398:
What are the shortest possible PLL algs, in terms of how long they are
when written down? This should be more interesting than just finding
move-optimal stuff, and I think there's a lot of room for creativity.
The most common algs may not be the shortest!
To start with, the following notations are OK:
- [P,Q] is a commutator (that is, P Q P' Q')
- [P:Q] is a setup move/conjugate (that is, P Q P')
- (P)n is P repeated n times; parentheses are unnecessary if it's clear what P is
- Any face or slice moves, rotations, or lowercase moves.
Also, the algorithm can do the PLL on any face, and you do not have to
include any adjustment at the end, or rotations at the very start/end.
And the shortest algs we found:
A: L'[F,R'B2R]L, L'[R'd2R,U]L (thanks to Stefan Pochmann)
E: [[RU'L:D2],U2] (thanks to TDM)
F: R'URU'R2F'U'FU[R,F]R2
G: [RL:U2][F'UB':d2], [R'UL',d2][BF:U2], L'R'U2LR[FU'B,d2], [LU'R,d2]B'F'U2BF
H: (M2U)6
J: [[RU'L:d2],U], [[R'UL':d2],U]
N: (r'DrU2)5, (rDr'U2)5
R: R[U2R'U2,UR'F'R]R', R'[U2RU2,U'RBR']R
T: [R2D':F2][B2D:L2]
U: M2uMu2MuM2, B2UMU2M'UB2
V: [F'UBU'F:U][U2,B]
Y: F2[DR2:U][R'U'R:F2]
Z: (UF2)6M'U2M (thanks to Moritz Karl)
20140629
Speedsolving Post: "Shortest" PLL Algs?
Speedsolving Posts: Almost-2gen LL Algs
From http://www.speedsolving.com/forum/showthread.php?18539 (January 2010):
From any ZBLL we can easily get to PLL using only 2gen moves. All PLLs
are a U, Z, or H perm away from either solved, R perm, or Y perm.
Therefore, if we can do R and Y perm with at most 2 D-layer moves, we
can do any ZBLL with at most 2 D-layer moves.
So, here is an R perm with exactly 2 D-layer moves:
R U2 R D R' U R D' R' U' R' U R U R' U
And here is a Y perm (but not an efficient one):
R' U' D (R' U' R U)3 D' U R (R U R' U R U2 R')2 U'
I imagine these algs could be very useful for OH - everyone loves 2gen
moves, and keeping D turns to a minimum is very helpful. Unfortunately, I
don't know of any way to generate optimal algs of this type. Does
anyone have an idea?
P.S. You can also do every ZBLL with
F (R U R' U')3 F' U (R U R' U R U2 R')2 U2
From http://www.speedsolving.com/forum/showthread.php?708&p=680961#post680961 (December 2011):
Dumping some optimal 2-F-move PLLs (there are probably a few optimal ones I missed but the optimal lengths should be accurate):
A-perm a HTM-optimal: 11f R U' R F2 R' U R' U' R2 F2 R2 QTM-optimal: 15q R U' R F2 R' U R' U' R2 F2 R2 A-perm a HTM-optimal: 11f R2 F2 R2 U R U' R F2 R' U R' QTM-optimal: 15q R2 F2 R2 U R U' R F2 R' U R'
E-perm
HTM-optimal: 18f R' U2 R U' F' R' U R' U2 R U R' U R2 F R' U' R R' U R F' R2 U' R U' R' U2 R U' R F U R' U2 R R U R' U R' F U' R2 U' R2 U2 R' U' R F' R' U R2 R2 U F' U R' U' R U R' U' R U R' U' R F U' R2 R2 U F' R' U R U' R' U R U' R' U R U' F U' R2 R2 U' R F R' U R U2 R2 U R2 U F' R U' R U' R' R2 U2 F' U' R' U R U' R' U R U' R' U R F U2 R2 R2 U2 F' R' U' R U R' U' R U R' U' R U F U2 R2 F U R2 U' R U R' U R2 U' R' U R' U' R U' R F' F U' R U' R U R' U R U2 R' U R' U' R U2 R' F' F U' R U' R' U2 R U' R' U R' U2 R U R' U R F' F U' R' U R' U' R2 U R' U R U' R2 U R U' R F' F R U2 R' U R U' R U2 R' U' R U' R' U R' U F' F R' U R' U R U' R U R2 U' R U' R' U R2 U' F' F R' U R' U' R2 U R' U' R U' R2 U R U' R U F' F R' U' R U' R' U2 R U' R U R' U2 R U R' U F' QTM-optimal: 20q R2 U F' U R' U' R U R' U' R U R' U' R F U' R2 R2 U F' R' U R U' R' U R U' R' U R U' F U' R2 F U R2 U' R U R' U R2 U' R' U R' U' R U' R F' F U' R U' R U R' U R U2 R' U R' U' R U2 R' F' F U' R U' R' U2 R U' R' U R' U2 R U R' U R F' F U' R' U R' U' R2 U R' U R U' R2 U R U' R F' F R U2 R' U R U' R U2 R' U' R U' R' U R' U F' F R' U R' U R U' R U R2 U' R U' R' U R2 U' F' F R' U R' U' R2 U R' U' R U' R2 U R U' R U F' F R' U' R U' R' U2 R U' R U R' U2 R U R' U F'
F-perm HTM-optimal: 15f R2 U R2 U2 F2 U R2 U2 R2 U R2 U' R2 U2 F2 R2 U R2 U' R2 U2 R2 U' F2 U2 R2 U' R2 U' F2 F2 U R2 U R2 U2 F2 U R2 U2 R2 U R2 U' R2 F2 U2 R2 U R2 U' R2 U2 R2 U' F2 U2 R2 U' R2 R2 U' F2 U2 R2 U' R2 U2 R2 U R2 U F2 U2 R2 R2 U2 F2 U' R2 U' R2 U2 R2 U R2 U2 F2 U R2 QTM-optimal: 19q R U R' U' R' U R U F' U R' U R U2 F R U' R' R U R' F' U2 R' U' R U' F U' R' U' R U R U' R' R U R U F' U' R U R' U' R' U2 F U' R' U2 R' R U2 R U F' U2 R U R U' R' U F U' R' U' R' R' U' R U' R' U R U R2 F' R U R U' R' F U R R' U' F' R U R' U' R' F R2 U' R' U' R U R' U R
G-perm a HTM-optimal: 15f F2 U R U2 R' U' R' U2 R2 U R' F2 R' U R R' U' F2 U R U2 R U2 R' U F2 U2 R U' R' QTM-optimal: 18q R U R' U' R' U F R U R U' R' F' U R' U2 R
G-perm b HTM-optimal: 15f R' U' R F2 R U' R2 U2 R U R U2 R' U' F2 R U R' U2 F2 U' R U2 R' U2 R' U' F2 U R QTM-optimal: 18q R' U2 R U' F R U R' U' R' F' U' R U R U' R'
G-perm c
HTM-optimal: 14f R2 U2 R2 F2 U' R2 U R2 U F2 U2 R2 U' R2 QTM-optimal: 17q R2 U' R U' R U R' U R' F' R' U R U' F R'
G-perm d HTM-optimal: 14f R2 U R2 U2 F2 U' R2 U' R2 U F2 R2 U2 R2 QTM-optimal: 17q R F' U R' U' R F R U' R U' R' U R' U R2
J-perm a HTM-optimal: 13f R' F R' U' R2 U' R2 U R' F' R U R2 R2 U' R' F R U' R2 U R2 U R F' R QTM-optimal: 16q R' F R' U' R2 U' R2 U R' F' R U R2 R2 U' R' F R U' R2 U R2 U R F' R F R' U R U' F' U R' U2 R U' R' U2 R R' U2 R U R' U2 R U' F U R' U' R F' R' U' R U F R U' R' U' R' U R2 U R' F' R' U' R U' R' U F U R' U' R F' R' U R2 R2 U' R F R' U R U' F' U' R U R' U R F R U' R2 U' R U R U R' F' U' R' U R
J-perm b HTM-optimal: 11f R U' F U' R' U' R U F' U2 R' R U2 F U' R' U R U F' U R' QTM-optimal: 12q R U' F U' R' U' R U F' U2 R' R U2 F U' R' U R U F' U R'
N-perm a HTM-optimal: 15f R2 U R2 U' R2 U' F2 U' R2 U R2 U F2 U2 R2 R2 U2 F2 U' R2 U' R2 U F2 U R2 U R2 U' R2 QTM-optimal: 21q R U2 R2 U' R2 F' R U R' U' R' F R' U R U2 R' R U2 R' U' R F' R U R U' R' F R2 U R2 U2 R' R U R' U R U' F U' R' U' R U F' U2 R' U2 R U' R' R U R' U2 R U2 F U' R' U R U F' U R' U' R U' R'
N-perm b HTM-optimal: 15f R2 U F2 U2 R2 U R2 U2 R2 U' R2 U2 F2 U' R2 R2 U' R2 U2 F2 U' R2 U2 R2 U F2 U2 R2 U R2 QTM-optimal: 23q? R U' R' U R' U2 R2 U R2 F2 U R U R U' R' U' F2 F2 U R U R' U' R' U' F2 R2 U' R2 U2 R U' R U R' R' U2 R' U' R2 U F' U' R U R' U' R2 U2 R F R' U R R' U2 F U R2 U2 R' U' R U R' F' R U2 R' U' R' U R R' U' R U R U2 R' F R U' R' U R U2 R2 U' F' U2 R R' U' R F' R' U2 R2 U R U' R' U F U' R2 U R U2 R
R-perm a HTM-optimal: 13f R2 F2 U R U R' U' R' U' F2 R' U R' R U' R F2 U R U R U' R' U' F2 R2 QTM-optimal: 16q R2 F2 U R U R' U' R' U' F2 R' U R' R U' R F2 U R U R U' R' U' F2 R2
R-perm b
HTM-optimal: 13f R2 F R U R U' R' F' R U2 R' U2 R R' U2 R U2 R' F R U R' U' R' F' R2 QTM-optimal: 16q R2 F R U R U' R' F' R U2 R' U2 R R' U2 R U2 R' F R U R' U' R' F' R2
T-perm
HTM-optimal: 14f R U R' U' R' F R2 U' R' U' R U R' F' F R U' R' U R U R2 F' R U R U' R' QTM-optimal: 15q R U R' U' R' F R2 U' R' U' R U R' F' F R U' R' U R U R2 F' R U R U' R'
V-perm HTM-optimal: 15f R2 U2 R2 U R2 U2 F2 U R2 U R2 U2 F2 U' R2 R2 U2 R2 U' F2 U2 R2 U' R2 U' F2 U2 R2 U R2 R2 U F2 U2 R2 U' R2 U' F2 U2 R2 U' R2 U2 R2 R2 U' R2 U2 F2 U R2 U R2 U2 F2 U R2 U2 R2 QTM-optimal: 19q R U' R' U R F R' U' R2 U R U' R U R2 F' R' R F R2 U' R' U R' U' R2 U R F' R' U' R U R'
Y-perm
HTM-optimal: 14f R2 U' R2 U F2 U' R2 U' R2 U F2 R2 U R2 R2 U' R2 F2 U' R2 U R2 U F2 U' R2 U R2 QTM-optimal: 19q R2 U' R2 U' R2 U R' F' R U R2 U' R' F R R' F' R U R2 U' R' F R U' R2 U R2 U R2 R' U' R U' R U' F U' R' U' R U F' U2 R2 U R R' U' R2 U2 F U' R' U R U F' U R' U R' U R