Seoul National University Optimizing a Personalized Multigram Cellphone Keypad

Current layouts for alphabetic input on mobile phone keypads are very inefficient. We propose a genetic algorithm (GA) to find a suitable keypad layout for each user, based on their personal text history. It incorporates codes for frequent multigrams, which may be directly input. This greatly reduces the average number of strokes required for typing. We optimize for two-handed use, the left thumb covering the leftmost rows and vice versa. The GA mini-mizes the number of strokes, consecutive use of the same key, and consecutive use of the same hand. Using these criteria, the algorithm re-arranges the 26 alphabetic characters, plus 14 additional multigrams, on the 10-key pad. We demonstrate that this arrangement can generate a more effective layout, especially for SMS-style messages. Substantial savings are verified by both computational analysis and human evaluation.