Cubetimer?

[signaly]

How exactly does cube timer get their scrambles? I mean is it just a random set of moves or is it something more specific?

[brunson]

Cubetimer.com? I believe they generate random sets of moves with some constraints to keep small sets of moves from undoing themselves.

[Johannes91]

Just a random sequence of moves, if I'm reading it correctly. Using a 3x3x3 solver and random position isn't easy in JavaScript.

[signaly]

Okay that makes sense but what about 180 degree turns wouldn't they undo themselves?

[Johannes91]

There are just two kinds of cancellations that scramble generators need to forbid: U U and U D U. Whether the turn is 90 or 180 degrees doesn't matter, just the face.

[signaly]

Oh, I see, thanks.

[Stefan]

Using a 3x3x3 solver and random position isn't easy in JavaScript.

Is it easier in other languages? If so, which and why? Or I should directly ask why it's not easy in JavaScript, because I know other languages but JavaScript not really. So does it have significant disadvantages?

[Johannes91]

Using a 3x3x3 solver and random position isn't easy in JavaScript.

Is it easier in other languages? If so, which and why? Or I should directly ask why it's not easy in JavaScript, because I know other languages but JavaScript not really. So does it have significant disadvantages?

I tried to write a solver that's reasonably fast and doesn't use too many moves a while ago, but gave up. I couldn't even get Thistlethwaite's algorithm working decently. Then I tried Haskell, and found it quite easy to implement Kociemba's algorithm and to make it find solutions shorter than 25 moves in less than a second. JavaScript is in my opinion more difficult, because:

* there are no native types, so tables take much more space than they need to;
* it's a very slow language, so without big tables the solver will be slow;
* if JavaScript code takes too long to finish, some browsers will freeze and/or terminate it.

There are many different implementations, of course, and the above points might not be true for all of them. I used SpiderMonkey for testing. And I'm far from an expert at JavaScript, it's very possible that I was just doing something stupid.

That said, it would be possible to connect to a server-side solver.

[cubetimer]

CubeTimer randomly picks a face on each iteration through a loop of the desired number of turns, but there are restrictions:

• Each time a face is turned, the possibility that the same face is selected for turning on a future iteration is disabled
• Once a face is disabled, it will not be turned again until enabled by the turning of an intersecting face

As far as I can figure, there is no chance for a move, or even a series of moves to undo itself. The one thing I'm not real happy with and will probably change soon is that a face does allow an opposite face to still be selected for turning. This is fine for something like U D, because they are in opposite directions, but in cases like U2 D2 or U D', it's the equivalent of just turning the equator.

There are no cases where moves will cancel each other out, but this case takes 2 turns to do the equivalent of one, which means you aren't REALLY getting a full 25 turns, sometimes.

[mrbiggs]

As far as I can figure, there is no chance for a move, or even a series of moves to undo itself.

A series of moves can, like (R U' R' U) x 6 or (R2 U2) x 6, unless I'm misunderstanding the algorithm.