Logical keyboard layout generator. Finds all keyboard layouts (or rather sets of columns) with (d)sfbs below a chosen threshold. For low thresholds does its job nearly instantly. Should work well as a way to filter out layouts on which to run slower analyzers (for example ones that use (d)sfb distance instead).
This is hopefully last rewrite of my generator. This time I cut everything I could out of it. I could have made it shorter, but I've decided to also try using 0 dependencies, which came out surprisingly well (did not result in a disaster).
While this generator can calculate weights of bigrams by itself, I strongly recommend supplying your own weights. I made sure the calculated weights aren't super bad, but don't expect more.
With cargo:
cargo run --release -- --precalculated --file monkeyracer_sfbs.json --cutoff 0.006Without --file the weights / corpus is loaded through stdio. Without
--precalculated generator calcualtes weights based on provided text as 4 * sfbs + dsfbs. --alphabet sets (if none is present) or overrides characters
placed on a keyboard.
To make exhaustive search feasible we are using two optimizations.
First, we are exploiting various symmetries. We don't distinguish between layouts with columns swapped or with keys swapped inside a column.
Second, instead of trying to go through all possible layouts ony by one, we look at groups of layouts instead. Specifically, we place characters on a keyboard in order of frequency untill we get complete layout or we cross the cutoff, at which point the whole group gets pruned. Because it's impossible for a layout to have less sfbs after adding another letter to it, we can be sure that all layouts we skip are above the cutoff point.
Number of column sets below percentage of sfbs on monkeyracer corpus. Weights taken from cmini repo. Percentages are normalized to bigrams containing only letters found on the layout.
| % | column sets |
|---|---|
| 0.5 | 70 |
| 0.6 | 14638 |
| 0.7 | 410645 |
| 0.8 | 5584638 |
| 0.9 | 48430687 |
| 1.0 | 299938617 |