Monday, August 23, 2010

El Reg: Linux kernel purged of five-year-old root access bug

Just a one line post, a link, and a reply to all the guy who claim that their OS is more secure than the others.

Posted via email from Past news & new news, thus updated often

Friday, August 13, 2010

Every position of Rubik's Cube™ can be solved in twenty moves or less.

From http://www.cube20.org/. With the help of Google cluster, scientists showed that any Rubik's Cube position can be solved in no more than 20 moves.


 

DateLower boundUpper boundGapNotes and Links
July, 1981 18 52 34 Morwen Thistlethwaite proves 52 moves suffice.
April, 1992 18 42 24 Hans Kloosterman improves this to 42 moves.
May, 1992 18 39 21 Michael Reid shows 39 moves is always sufficient.
May, 1992 18 37 19 Dik Winter lowers this to 37 moves just one day later!
January, 1995 18 29 11 Michael Reid cuts the upper bound to 29 moves by analyzing Kociemba's two-phase algorithm.
January, 1995 20 29 9 Michael Reid proves that the ''superflip'' position (corners correct, edges placed but flipped) requires 20 moves.
December, 2005 20 28 8 Silviu Radu shows that 28 moves is always enough.
April, 2006 20 27 7 Silviu Radu improves his bound to 27 moves.
May, 2007 20 26 6 Dan Kunkle and Gene Cooperman prove 26 moves suffice.
March, 2008 20 25 5 Tomas Rokicki cuts the upper bound to 25 moves.
April, 2008 20 23 3 Tomas Rokicki and John Welborn reduce it to only 23 moves.
August, 2008 20 22 2 Tomas Rokicki and John Welborn continue down to 22 moves.
July, 2010 20 20 0 Morley Davidson, John Dethridge, Herbert Kociemba, and Tomas Rokicki prove that God's Number for the Cube is exactly 20.

 

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