# 7x7 Parity and Centers



## d_sprink (Jan 10, 2009)

Ok, its not related to Speed-solving, hardware, or the other categories, and I'm not a complete beginner. It's about the 7x7.

When I learned big cubes, I had always solved opposed centers in pairs. This whole "one center at a time" idea is very novel to me. I didn't have commutators with my system; I didn't have too many issues at all actually, yet somehow it was a little bit harder (especially on the last two). If I were to explain the system, would anyone out there be interested in giving it a shot to compare times with? Would anyone want to give it a shot out of curiousity? It's a billion times faster (hyperbole) on the 4x4, but I haven't timed myself on anything due to the lack of a decent timer. Would anyone care to hear about this method?

Another thing about the 7x7x7- Edge parity. I use reduction (if you couldn't tell), and when solving the edges, I first make a 3 block long edge in the center of every edge, and then extend both sides out one, making it 5. Wow, I'm awful at explaining. In any case, I've noticed the parity seems to come in pairs - if you have a parity issue on the inner edges, you'll get a parity issue on the outer edges as well. Does everyone else experience this? Or is there a different method that everyone else out there uses that makes my parity question inapplicable? It's not a problem, its just a pattern I noticed and thought I would point out.

I know I'm not the best at explaining things, but i hope you find this makes sense. Thank you for your time.


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## b03tz (Jan 10, 2009)

> but I haven't timed myself on anything due to the lack of a decent timer



rubetimer.com


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## Siraj A. (Jan 10, 2009)

_Speedsolving_: "General discussion about speedsolving the Rubik's Cube and other twisty puzzles. Discuss new algorithms, methods, share your records, keep each other updated with the latest speedcubing news."


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## Dene (Jan 10, 2009)

Firstly: This should either be in speedcubing or beginners section, whether it is about speedsolving or not, or whether you are a beginner or not.

Secondly: One center at a time is the only prastical way to do the bigger cubes (except the last two centers of course).

Thirdly: We call that method of edges "inners then outers", or samething along those lines. I don't know the mathematics of parity unfortunately, but I guess it makes a difference whether you do AVG edges, or freeslice.


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## b03tz (Jan 10, 2009)

Siraj A. said:


> _Speedsolving_: "General discussion about speedsolving the Rubik's Cube and other twisty puzzles. Discuss new algorithms, methods, share your records, keep each other updated with the latest speedcubing news."



General discussion about speedsolving *(It's a billion times faster)* the Rubik's Cube and other twisty puzzles* (It's about the 7x7.)*. Discuss new algorithms, methods *(when solving the edges, I first make a 3 block long edge)*, share your records *(but I haven't timed myself on anything)*, keep each other updated *(Would anyone want to give it a shot out of curiousity) *with the latest speedcubing news."


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## blade740 (Jan 10, 2009)

Well, some call it "multi-reduction" You're essentially reducing the edges to a 5x5, then a 3x3. 

Your parity situation, however, is wrong. There are essentially 2 separate parities on the 7x7. Each one has an independent 50% chance. So if you get inner parity, you still have a 50% chance of not getting outer parity.


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## d_sprink (Jan 12, 2009)

Thank you blade, for the topical response. So you do have the 50% for each edge pair independant of the other? I've never experienced this, I guess I'll keep trying 

If one person tells me that I'm in the wrong section, I don't need two more people to tell me that. Please refrain from repeating other people so you can feel good about yourself.

And "One center is the only prastical way to solve the centers..." or whatever you said. I'm glad that's your opinion; I'm glad you won't give anything else a shot. At least use proper spelling while shooting me down; it makes you look foolish and close-minded when you don't.

If nobody cares, and all I get are posts telling me to move this to a different section (if its possible for a mod to bump this over, that would be appreciated...), I'm off to a new forum. Be civil, people. That's all I ask.


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## Dene (Jan 12, 2009)

d_sprink said:


> If one person tells me that I'm in the wrong section, I don't need two more people to tell me that. Please refrain from repeating other people so you can feel good about yourself.



Perhaps if you were less arrogant and thought about it, you would have noticed that the 3 posts were all made at the same time.


d_sprink said:


> And "One center is the only prastical way to solve the centers..." or whatever you said. I'm glad that's your opinion; I'm glad you won't give anything else a shot. At least use proper spelling while shooting me down; it makes you look foolish and close-minded when you don't.


Oh my, a typo deary me it's the end of the world. How was that not obviously an innocent mistake? How about you try using some grammar, idiot.
Of course one center at a time is the only practical way to solve a 7x7x7 center. Have you not even thought about how much there is to do?



d_sprink said:


> Be civil, people. That's all I ask.


I was trying to be nice by giving you a well thought out and constructive answer, but clearly you're just a grumpy bum so take my advice and stop crying.


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## AvGalen (Jan 12, 2009)

I don't know why this is now in off-topic, but blade740's answer is correct and Dene's is sort-off correct.

Inner-edges are completely independent to outer-edges.
If you solve centers first you have 50% chance of getting inner-parity and 50% chance of outer-parity. It doesn't matter which method you use to pair them up.

The reason I say Dene is sort-off correct is because if you solve inner+outer edges at the same time (bigcubes.com method) you *could *also solve inner+outer parity at the same time (like a Z-Perm on 3x3x3 coule be considered double parity or no parity). *If *you consider this, these are your odds about parity:

AVG: 25% no parity, 25% only inner, 25% only outer, 25% both
Bigcubes: 50% no parity, 25% only inner, 25% only outer

To Dene and the TS: Cool down, both of you


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## Dene (Jan 12, 2009)

Hmm see I wasn't sure because with AVG I believe you only get one or two types of parity whereas with freeslice there are more?


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## AvGalen (Jan 14, 2009)

Dene said:


> Hmm see I wasn't sure because with AVG I believe you only get one or two types of parity whereas with freeslice there are more?



There are only the two above types of parity on odd cubes. But they can be hidden in many more ways when you don't finish with a semi-pair 2-swap.
Just like PLL-Parity on 4x4x4 can be hidden in many more ways when you don't have corner PLL done.


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