understand parity

[rjohnson_8ball]

okay so the algs should be:

r U2 r U2 r U2 r U2 r
r2 U2 r2 2D2 l2 2D2 U2

Hm I looked closer into these algs and I'm kinda confused:/
The first one solves the OLL parity and the second solves PLL parity.(at least I think so...)
But I'm a bit confused about how they work.
The first one does an even number of swaps on centers(2) and an uneven number of swaps on the edges (3).
The second one does an even number of swaps on centers (4) and an even number of swaps on the edges (2).

Did I miss something there?

Tracking the individual cubies might help. If you look at the result of the 1st alg, you will see 2 edge cubies orbited by 180 degrees and 2 edge cubies orbited by only 90 degrees. I think there are 5 center pairs involved; on each "r" slice 4 center pairs get orbited by 90 and 1 gets shielded on L portion of the U face. After 5 "r" slices, each of the 5 center pairs gets shielded once, resulting in 5*(4/5)*90 = 360 degrees for each center pair. Yes, I might be confused too.

I do the 2nd one differently for PLL parity, although mine is equivalent to yours: r2 U2 r2 Uw2 r2 u2. It seems to me that it swaps 3 pairs of individual edge cubies (there are three turns on U) and also puts the centers back.

 

[Die_d00pel_Null]

Yeah, you missed the part that explains that swaps on centers are not what parity is about. The first alg doesn't change centers, but has 5 quarterturns in it which is odd so it changes parity (very simplified)

Uhm the first alg does changes on the centers and ryan heise just mailed me that switches on the center are what parity is about. So either I'm misunderstanding something here or one of you is wrong...

And the second alg for pll parity has an even number of quarterturns.

rjohnsons explaination helped a bit btw

 

[Stefan]

ryan heise just mailed me that switches on the center are what parity is about.

Liar.