Rubik's Cube

collect the Rubik's cube from any initial state can be no more than 20 moves. To such conclusion the group of American researchers led by Professor Morley Davidson of the University of Kent, Ohio, who with the help of Google computers try all possible combinations of the puzzle. As a result, as reported by RIA Novosti, it turned out that the so-called "God's number", the minimum number of moves to assemble the Rubik's Cube from any starting combination is 20. "Now we know what the magic number - that's 20," - said Davidson. Until 1995 it was thought that the theoretical minimum for the assembly of popular puzzle is 18 strokes, but the mathematician Michael Reid found the original configuration of a Rubik's Cube that can be collected only 20 moves. According to Davidson, since it was believed that "God's number" is equal to 20, but this assumption was based solely on the belief of scientists: anyone not previously been able to check all the configuration of the puzzle. "We secretly hoped that during the tests we find the combination for which the necessary course of 21" - Davidson said. To solve this problem, scientists have broken all possible initial states about 2, 2 billion groups of 20 billion variants in each - so much conditions in the classic Rubik's Cube. Identifying identical and symmetrical condition, the researchers reduced the test set up 56 million groups. Google Inc. offered its fleet of computer scientists to test all of these combinations. According to Davidson, a good desktop PC quad-core Nehalem microarchitecture and a clock speed of 2 GHz 8 it would take about 35 years of computer time. The scientists have published their findings on the Internet and are going to prepare an article for a scientific journal. According to them, the code will be able to test any owner of a small supercomputer. The researchers themselves are going to continue to work and, in particular, to find "God's number" to other options puzzle.

Source: mirfactov.com/