# Chris Tran Last Slot (CTLS) Recognition System



## gyroninja (Dec 17, 2015)

Over the past few weeks I've been working on a recognition system for CTLS. You can access my third revision of my recognition system here. My previous systems either ran into flaws or were incomplete. In this document I've put some strategies at figuring out the ZBLL that you have. CTLS solves 13,804 1LLSLL cases. I think CTLS could have a lot of potential if you can get the recognition down. Even if full CTLS is not worth it 2GCTLS (CTLS but with just 2GLLs) is very good. Another interesting variant of CTLS is 2GCTOLS. 2GCTOLS (2 Gen Chris Tran Orient Last Slot) uses OCLL+1. (31 2GLL algs) After the OCLL+1 alg you will just have EPLL afterwards. While 2GCTOLS can only be done when the corners are permuted it shows up more often than normal CTLS. CTLS requires a corner edge on the U face to be solved relative to each other. 2GCTOLS on the other hand only requires a corner and edge to be oriented next to each other.

I've poured almost everything I've learned about CTLS so far into this document. If anyone has any questions or incite about CTLS don't be afraid to say something.


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## 4Chan (Dec 17, 2015)

I told some people at comps this, but the 2gen version has some sick recognition actually.
By looking at how the "odd/F2L" edge moves, you can figure out the whole edge cycle immediately. Without even tracing the whole edge cycle, just from where it needs to go. Example: UL to UR

Also, all you need for the orientation recognition is the ULB and ULF corners.
Just by looking at ULB, you can narrow down tons of cases, then after looking at ULF, you'll know the case.

It's really cool that you're looking into this!

EDIT: You did a really cool job!


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## gyroninja (Dec 17, 2015)

4Chan said:


> I told some people at comps this, but the 2gen version has some sick recognition actually.
> By looking at how the "odd/F2L" edge moves, you can figure out the whole edge cycle immediately. Without even tracing the whole edge cycle, just from where it needs to go. Example: UL to UR
> 
> Also, all you need for the orientation recognition is the ULB and ULF corners.
> ...



The corner orientation thing is actually really interesting. I assume you just mean looking at the normal corners and one of the corners affected by the setup move. After looking at those three corners it will be at most two different cases.

Edit: Looking back at what I said. If you look at three corners you don't have to see the last one. There would only be one case.


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## 4Chan (Dec 17, 2015)

I had a document somewhere, but I gave up on the recognition system.
I've got some free time on Friday, I'll make a short video and post in this thread 

It's super flattering that you took the time to do this, for real! I'm mega honoured to have been mentioned!


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## megaminxwin (Dec 17, 2015)

That's _insane._ I'd have to see an example solve or something, I still don't really get it...

*pokes jabari nuruddin* you know you want to


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## sqAree (Dec 17, 2015)

megaminxwin said:


> *pokes jabari nuruddin* you know you want to



So as far as I understood this method can only be applied in 7/32 of all 1LLSLL cases?

Why not just learn algs for every 1LLSLL case?


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## gyroninja (Dec 17, 2015)

megaminxwin said:


> That's _insane._ I'd have to see an example solve or something, I still don't really get it...
> 
> *pokes jabari nuruddin* you know you want to



Here's an example solve.

Scramble: F2 R' U' F' L' D2 B' R2 U2 D L' D2 R D2 F2 R' U2 R' D2 R2 F2

R' F (U' D) L' F D' R D // EOLine
R U' L2 // LF Block
R U R' // RF Block
L U L' U2 (L U' L' U)2 // Left Block
// I'll break down the CTLS for you
U R' // Create pseudo F2L
L' U2 R U' R' U2 L R U' R' U' // ZBLL - L Diag
R // Undo pseudo F2L
U // AUF



sqAree said:


> So as far as I understood this method can only be applied in 7/32 of all 1LLSLL cases?
> 
> Why not just learn algs for every 1LLSLL case?



This is 7/32 of 1LLSLL with edges pre oriented. CTLS only uses 493 algs (ZBLL). Algs for every 1LLSLL cases would be very hard to do as the case count is in the millions.


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## shadowslice e (Dec 17, 2015)

Hmmm... Maybe this could be good for the Briggs method (v1) where you may only need to 2-gen CTLS cases. Because that would bump the movecount to sub-40 potentially.

VGJ with the recog system btw!  

I may actually get around to learning the system if not the algs.


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## gyroninja (Dec 19, 2015)

Due to a resent update in my timer. (Well a modified version of qqtimer but whatever) You are now able to specify a custom scramble input for CTLS scrambles if you ever feel like practicing it. You can practice your CTLS here.


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## 4Chan (Dec 19, 2015)

Here are a few examples. Sorry for the low volume, I'm sleepy and I forget my ipad doesn't pick up audio really well.

For other people who want to see CTLS, check out my other video, here is is below:







If you don't want to watch the videos, i'll summarise with words:
Pretty much, you just put the corner where it needs to go, and then you ignore the bad edge and the incorrect R layer, and then you just use normal ZBLL recognition systems like Baum-Harris, edge cycles, blocks, etc.

The bad edge is really obvious and if you recognize by edge cycle, it's really straightforward easypeasy.
Orientation is silly because it's obvious too.


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## gyroninja (Dec 19, 2015)

4Chan said:


> https://www.youtube.com/watch?v=_mEK1-7yrdA
> 
> Here are a few examples. Sorry for the low volume, I'm sleepy and I forget my ipad doesn't pick up audio really well.
> 
> ...



Wow this recognition is a lot better than what I came up with. You've been giving me some cool ideas for what to do with my 4th revision of my recognition.


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## 4Chan (Dec 19, 2015)

Your post and stuff actually made me think. Thank you so much for making this post!

EDIT: Nope nope nope, this is too hard to recognize for speed to be worth it, I give up again.


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## b0ssGuy23 (Dec 23, 2015)

4Chan said:


> Nope nope nope



This is the second time I hear a reference from Noah GJoiners channel today xDDD

Sorry Noah, I had to point that out.


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## YouCubing (Dec 23, 2015)

b0ssGuy23 said:


> This is the second time I hear a reference from Noah GJoiners channel today xDDD
> 
> Sorry Noah, I had to point that out.



You do realize that that's an actual thing, right? -_-


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## 4Chan (Dec 23, 2015)

I totally forgot one last example:

When the block is in the other direction, and especially if you do ZZ and you have a 1x1x2 in the last slot (more common than one would expect), you can just herpderp into a ZBLL and solve everything. Alternately, if you have the 1x1x2 block, just do the setup, and proceed.

*Example:*

*Scramble:* R U' R U2 R U R2 U2 R U R U' R2 U2 R2 U' 

*Block*: U R U' R U2 R2 (NOTICE THE LAST SLOT, THIS IS THE CASE I MENTIONED)

*CTLS* (ZBLL_+fix_): y R2 B2 R U2 R U R' U R' B2 R2 + _y' U2 R U R' U_

The recognition for this is really simple, there's a 2x2x1 block on the left side that needs to be made, and like, the corner tells you which edges to get there in order to make it, and then you just think of which ZBLL makes that 2x2x1 block, and then you just make it, and then everything solves. The "bad" edge also gives you a hint to the edge cycle, making it pretty trivial to figure out.
I'll make a video soon, if that above example wasn't enough


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## gyroninja (Dec 23, 2015)

4Chan said:


> I totally forgot one last example:
> 
> When the block is in the other direction, and especially if you do ZZ and you have a 1x1x2 in the last slot (more common than one would expect), you can just herpderp into a ZBLL and solve everything. Alternately, if you have the 1x1x2 block, just do the setup, and proceed.
> 
> ...



Interesting concept but if you have a 2x1x1 in the last slot like in the example why don't you just do R U R' F' to setup to do a normal ctls.


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## 4Chan (Dec 24, 2015)

F moves complicate things because they break orientation.

Generally speaking, you can't use a ZBLL once orientation is broken and it influences an edge that goes into the face that has broken orientation.

Unless the edge cycle doesn't move into the F/B face, then you can use a normal ZBLL, otherwise you'd have to use a 1LLL alg.
I actually thought of that too back in 2009 when I came up with this LOL

EDIT:

Here's a video example:


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## gyroninja (Dec 24, 2015)

4Chan said:


> F moves complicate things because they break orientation.
> 
> Generally speaking, you can't use a ZBLL once orientation is broken and it influences an edge that goes into the face that has broken orientation.
> 
> ...



If you insert the f2l edge you are now able to use any side's face turn to setup. When the left block is still in U there is one location for the f2l edge that takes a long time to setup. The other locations takes like 4 or 5 moves for the initial setup. Which isn't too bad.


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## Daniel Lin (Jul 2, 2016)

wow this is really cool, I'm considering learning it.
I really don't get how it works though
so you just ignore the R layer and the bad edge, right?
But I can't recognize the case using Baum Harris/color blocks because i can't recognize ZBLLs from all angles. I have to AUF the CO case a certain way. For example, for Chameleon and Headlights I always make it face the back. After I AUF, I always look at the same pieces:FU, FRU, RU, RUF. But then some of those pieces can be R layer pieces or the bad edge. So how do I recognize the case?


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## gyroninja (Jul 2, 2016)

Daniel Lin said:


> wow this is really cool, I'm considering learning it.
> I really don't get how it works though
> so you just ignore the R layer and the bad edge, right?
> But I can't recognize the case using Baum Harris/color blocks because i can't recognize ZBLLs from all angles. I have to AUF the CO case a certain way. For example, for Chameleon and Headlights I always make it face the back. After I AUF, I always look at the same pieces:FU, FRU, RU, RUF. But then some of those pieces can be R layer pieces or the bad edge. So how do I recognize the case?


In your mind twist the corners that will be on the R layer in the end to be up to create a proper ocll. Once you have that ocll made in your mind you auf to where it says in the doc and recognize the cp case you have. Then you look at the pieces that are already solved and match those pieces to a diagram in the doc.


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## 4Chan (Jul 2, 2016)

Oh guys, thanks for bumping this, because I figured out something cool.

Non-Matching Blocks CTLS is even more sick, because instead of 2 block choices, you have SIX block choices, and it leads to really sick FMC solves. Since you don't have to worry about which blocks to build.


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## gyroninja (Jul 2, 2016)

4Chan said:


> Oh guys, thanks for bumping this, because I figured out something cool.
> 
> Non-Matching Blocks CTLS is even more sick, because instead of 2 block choices, you have SIX block choices, and it leads to really sick FMC solves. Since you don't have to worry about which blocks to build.


You mean like finishing the solve with L R for example?


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## 4Chan (Jul 2, 2016)

Oh ummm, try this quick example I just made
It's not optimized move count wise, it's just whatever I saw first.

*Scramble:* B2 F2 L U2 R' U2 L B2 U2 F' L2 R2 D' B2 D' F L F2 R'
(LINE ON BOTTOM)

*EOLine:* R' B' L B F' D R2 D'
*Block:* R2 L2 U2 L2 U2 L' U L U L'
*Non-Matching Blocks:* U R' U R' U' R U2 R U R U _(looks messed up)_
*Setup:* R
*CTLS:* y2 R' U2 R2 U R2 U R2 U2 R'
*Fix:* U2 L' U' L2

Edit: The way I recognise the case is that like, I figure out the "fix" from how to get the non-matching blocks to the solved state, then I do the inverse on a solved cube.
Then I figure out what ZBLL will bring the scrambled cube to the same state as the inversed "fix". Then I do this to the cube and hope for a cancellation.

So then if the first non-matching block was like, 15 moves, I test the other non-matching blocks (1 per corner), and see which gives the lowest solution, and then I write that down on my FMC sheet.


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## LexCubing (Apr 26, 2017)

I'm from the future. Have you tried doing it using TTLLs. How many LSLL cases does it solve?


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## gyroninja (Apr 26, 2017)

LexCubing said:


> I'm from the future. Have you tried doing it using TTLLs. How many LSLL cases does it solve?


It don't work because they don't effect co, making recognition a lot harder.


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## LexCubing (Apr 27, 2017)

gyroninja said:


> It don't work because they don't effect co, making recognition a lot harder.


So recognition will suck but what about execution?


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