• Welcome to the Speedsolving.com, home of the web's largest puzzle community!
    You are currently viewing our forum as a guest which gives you limited access to join discussions and access our other features.

    Registration is fast, simple and absolutely free so please, join our community of 40,000+ people from around the world today!

    If you are already a member, simply login to hide this message and begin participating in the community!

3x3x3 PLL recognition using only two sides

petero2

Member
Joined
Aug 3, 2009
Messages
2
I finally decided to learn PLL recognition using information from only two sides. Since I didn't find any computer help for learning this, I decided to implement it myself. (I know about "Drill Sergeant", which is good for practicing recognition + execution, but not perfect if you only want to practice recognition as efficiently as possible.)

I decided to use "Anki", http://ichi2.net/anki/, and I have created two "decks". One deck is called "Rubik's cube PLL decision tree" and helps you memorize the decision tree I use for recognition. The other deck is called "Rubik's cube PLL recognition", and lets you practice recognition for all the 288 possible PLL states.

Example question:
pll034Q.png

and the corresponding answer:
pll034S.png


The images were generated by a quick and dirty python program that I wrote: http://web.telia.com/~u89404340/rubik/pll.py

In case you don't want to use anki, but are still interested in the decision tree, here is a link to a text description. I hope it is understandable:
http://web.telia.com/~u89404340/rubik/pll_decision_tree.txt

I'm sure there are many different ways to create the decision tree, and my way is probably not the best possible way. However, I hope that with enough practice, I will be able to "instantly know" the PLL state without using any concious thinking. When I reach that state, the decision tree will largely become irrelevant.

I'm not there yet though. My average time with my old recognition method (look at all sides and identify blocks) was about 24s. When using 2-side recognition, my median time is currently about 29s.

I also have a question. Together with the 2-side recognition, I also stopped doing cube rotations before the PLL. However, in some cases this means I have to do for example "U + alg + U'" instead of "rotation + alg". Any opinion on which is faster? One cube rotation or two U turns?
 

miniGOINGS

Member
Joined
Feb 27, 2009
Messages
3,049
I calculated 336 different states.

EDIT: 340 If you're including solved.
 
Last edited:

petero2

Member
Joined
Aug 3, 2009
Messages
2
recognition for all the 288 possible PLL states.
FAIL..... 21 to be exact.


There's a difference between cases and states. Whilst I don't know the actual number, it's definitely greater than 21 (also, you're forgetting solved, which would make 22 by your logic).

There are 4! = 24 ways to permute the corner pieces, and equally many ways to permute the edge pieces. However, because of corner/edge parity, only half of the possible states are reachable without taking the cube apart. This yields 24*24/2 = 288 PLL states.

However, for recognition, you can immediately cut that down by a factor of 4, by using recognition algorithms that don't use "absolute" colors. That is, you formulate your recognition rules in terms of "relative" colors, for example "if stickers 1,2,3 have one color, stickers 4,5 another color, and sticker 6 a third color, then you have a J permutation".

Also by using mirror symmetry, you can reduce the number of "recognition cases" even more, perhaps down to about 40 (depending on your decision tree and how you count, I suppose).
 

miniGOINGS

Member
Joined
Feb 27, 2009
Messages
3,049
[offtopic]Using only 6 edge pieces, how many possible permutation states are there? Is it 360?[/offtopic]
 

ross mccusker

Member
Joined
May 1, 2009
Messages
32
Location
kilmarnock, scotland
recognition for all the 288 possible PLL states.
FAIL..... 21 to be exact.

yes there are 21 PLL's however

I think he ment all the possible places each PLL can lie. a PLL can lie in 4 possible possitions on the top layer there for can be executed from several different angles. think as a cuber he knows that there are only 21 possible pll cases.

so dont jump in and shout fail just yet!
 
Top