Is 20 turns enough for a scramble?

[ben1996123]

use computer generated scrambles then

 

[peterbone]

If you're scrambling by hand then you can never reach a completely random scramble. 20 is probably enough though. If you use a computer generated scrambler that uses random state selection (not all scramblers use this) then 20 is always enough for a completely random scramble.

 

[kinch2002]

That would never happen, as the WCA scrambler is optimal.

I'm afraid that's not true

 

[TMOY]

Define completely scrambled?

You can say it's 20 since some of the 'hardest' scrambles will need the full 20 moves to solve optimally (referring to God's number.) But it obviously depends on what moves you do, since you can scramble a cube fairly well with 10 moves - U L R' D F R2 B D R F

Yep. God's number is irrelevant here, since there are way more possible scrambles than what you will be able to solve in your entire life, you don't need to be able to reach all of them. IMHO a good scrambling must fulfill the following two conditions:
- same proportion of lucky solves as a completely random scrambling;
- you don't geat repeatedly the same scrambles.

10 moves is probably not enough, but IMHO 20 moves is. When I handscramble though, I usually prefer to play safe and perform something like 30-40 moves or so (at least with a good cube, with a crappy storebought I tend to stop earlier).

 

[Renslay]

And always make sure to "break your habit", i.e., don't repeat movements / algorithms / sequences without thinking.

 

[mark49152]

And always make sure to "break your habit", i.e., don't repeat movements / algorithms / sequences without thinking.

This is hard and is the reason hand scrambling is less reliable. I try to use all 6 faces; include cw and ccw turns; include double turns; turn opposite faces consecutively; rotate every few moves in case I am favouring faces or patterns; don't look at the cube while scrambling; and use about 30+ moves. I try to emulate computer scrambles, so plenty of practice with those helps.

 

[jayefbe]

This is hard and is the reason hand scrambling is less reliable. I try to use all 6 faces; include cw and ccw turns; include double turns; turn opposite faces consecutively; rotate every few moves in case I am favouring faces or patterns; don't look at the cube while scrambling; and use about 30+ moves. I try to emulate computer scrambles, so plenty of practice with those helps.

I agree, and do many of the same things whenever I do scramble by hand. I try to avoid hand scrambling whenever possible because it can be so difficult to avoid these repetitive movements. Plus, I want know that a good solve is not simply due to poor scrambling. I personally wouldn't call a hand scrambled solve a pb, and I always take someone else's hand scrambled times with a grain of salt.

 

[cannon4747]

When I use a scramble generator, I have it at a set number of moves for each puzzle and take whatever it gives me. Hand scrambling, I scramble it for a while, then close my eyes and randomly turn it for a few seconds. I accept whatever scramble I have when I open my eyes. Make sure to throw in a few random cube rotations and to do it for longer amounts of time with bigger cubes.

 

[TMOY]

And always make sure to "break your habit", i.e., don't repeat movements / algorithms / sequences without thinking.

That's the main reason why I use more moves than needed. More moves = less chances to always do the same thing.