Reduction Method

Reduction is a prevalent method for solving big cubes, which involves solving centers and assembling edges so that the cube is "reduced" to a 3x3x3 puzzle. All recent official records and fastest times on the 4x4x4 and 5x5x5 cubes have been set by solvers using reduction.

The idea of reduction is applicable to other puzzles, where it may be easier to manipulate a puzzle so it functions as a simpler sub-puzzle. In most cases, reduction is used to simplify the puzzle by grouping pieces first, instead of directly solving pieces into their correct positions.

The idea of reduction can sometimes be formalized as effectively as placing a puzzle in a smaller subgroup. Thistlethwaite's algorithm was based on several iterative reductions, and most fast computer solvers essentially use those approaches.

Although most solving methods involve steps that reduce the left-over puzzle portion, simply solving the puzzle into "less of a mess" (such as reducing a cube to [Last Layer|LL]] with Petrus) is not commonly considered reduction. The term is more applied to solving a puzzle into a differently interpretable puzzle, which is normally solved without resort to treating it like the original puzzle (with notable exceptions, such as Parity).