Unravel

The first thing to observe is that the state of a cube is completely defined by what can be seen on its six external surfaces. For a cube of size n, the state is completely defined by the colors of n x n x 6 miniature squares.

It follows that the current state of the cube can be simply observed on a computer screen by displaying six flat two-dimensional faces each with n x n elements. This approach has been adopted for the Unravel software available for download and has also been used by other programmers.

While the two-dimensional display lacks a real-world look, it actually makes solving the cube easier than some implementations because all cube elements are visible all the time. Of course, all the rules that apply to the real-world cube have to be implemented in the software.

Central to the Unravel cube solution software is the adoption of keyboard text entry as the means by which the user manipulates the state of the cube. A useful addition to the cube software is the introduction of some shortcuts.

The conventional approach is to advance in 90 degree rotation steps of one or more layers throughout the solution process. Computers are ideally set up to allow sequences to be defined in "macros".

The term "macro" as used in computer science is a rule or pattern that specifies how a certain input sequence should be mapped into an output sequence. Macros are normally used to map a short string to a longer string (sequence of instructions). Macros simplify things in Unravel by providing short-cuts for long sets (or frequently used short sets) of instructions on how to rotate the cube.

Implementation of macros is achieved via keyboard entry. On average, macros are not of much use until about 40% of the cube is in place and most are used for centre element placement (centre elements become numerically dominant for n greater than 4). The default macro set included with the Unravel software provides just one of many paths to a solution.

The macro sequences provided for cubes of size 4 and above may not be as short as some published sequences. It needs to be emphasized that I was looking for "a" solution, not necessarily the solution with the least number of moves. From a computer standpoint, short or long macro sequences can be executed "instantly". Users can write and use their own macros, or not use any macros, if they wish.

An essential addition to cube software, particularly for cubes of large size, is the provision of the capability for users to save the state of their partially arranged cube on their disk or other storage medium, and be able to readily recover it at a later time.

For cubes of large size it would be safe to say that non-specialist cubists would not want to rely on being able to solve the cube in one sitting. I have used the Unravel program to unscramble cubes only up to size 15x15x15 as my interest has been more in programming the means to solve the cubes rather than in implementing the means.

For those who have an interest in the time they take to solve a cube, an elapsed timer is provided. "Processor" time is logged separately to "user" time, so a slower computer does not give rise to any penalty.

Keep your eyes on the clock because you are being timed.. The elapsed time display can be turned off if desired.