Now that the Systematic Sudoku blog has completed its trek through the advanced Order of Battle, Sudoku writing and hard puzzle collections can be reviewed from the perspective of Systematic Sudoku. This means to evaluate them in regard to the human engineered techniques explained and illustrated in this blog.
The reviews will evaluate claims and theories about human Sudoku solving from a sysudokie perspective , and will grade puzzle collections on a sysudokie scale of difficulty. Reviews will also give me an opportunity to link back into the basic and advanced techniques sections of the blog, roughly the 2012 posts, for definitions and explanations related to the review.
Rather than colorful but subjective labels like “extreme” or “diabolical”, the reviews will grade collections according to the phase of the SSOB in which the puzzles tend to reach at point of collapse. The grade levels currently are:
basic: via dublex, cross hatch, locked sets, boxline, or X-wings.
bv scan: Sue de Coq, APE, UR, XYZ-wing, or XY-chains
x-panels: X-chains, regular, finned and mutant fish
coloring: Medusa coloring and bridging
AIC net: Extended XY-chains, XY and AIC hinged networks
ALS net: systematically enumerated ALS and ALS aided AIC
Limited pattern overlay : a scaled back but systematic version of POM
The Survey Table
Puzzle collection grading and commentary will be based on a survey sampling of 10 puzzles, preselected arbitrarily by a random digit and taking every tenth puzzle, starting with the digit. Data from this survey is presented in a survey table that summarizes the solving experience in box marking, line marking, and advanced levels.
Puzzle collection numbers are listed in the left column, with each puzzle having a line entry in the table.
From left to right, the table has the following column headings and contents:
The “Start” column records the number of starting clues.
The “Box” column shows the numbers of new clues, then the slinks or aligned triples added in box marking. A slash character separates clues from slinks. An aligned triple is counted as a slink, because in further marking, it has comparable power to exclude candidates from cells. The completion of a naked pair is counted as one slink. The column also mentions any noteworthy patterns typically found in box marking, which contribute to candidate exclusions.
The “Line Marking” column contains an abbreviated history of the line marking. At each successive free cell level encountered, basic solving events are listed, along with the numbers of clues and slinks they generate. Noted basic solving events include naked and hidden singles(ns,hs), pairs(np,hp), triples(nt,ht), quads(nq,hq) and quins(nqn, hqn), boxlines(bxl), hidden double line exclusions (hdx), and X-wings(x).
The line marking history shows the numbers of lines marked at each free cell level. A free cell level is 9, minus the number of cells reserved by clues and locked sets within the line. It reflects the difficulty of marking that line, and line marking proceeds by increasing free cell level, easier lines first. When an event generates new markings, the same “clue/slink” results follow the event, in parentheses.
To illustrate the line marking history, let’s read this one:
Commas separate one free cell level from the next. Line marking started with 4 free cells(typically 5 clues). Five lines were marked routinely, then a naked triple occurred on the next line, resulting in 3 clues and 2 slinks(counted as described above). Two more level 4 lines were then marked. At the 5 free cell level, a boxline produced one clue. One slink would have been “(0/1)”. Three more lines followed at 5 free cells. Then line marking ended on a naked pair, the second line with 6 free cells.
When line marking is completed and the bv scan techniques begin, the number of bv left by line marking is reported in the next “bv” column. Aside from UR detection, the bv scan techniques depend on a sufficient number of bi-value cells.
Advanced solving events are described in the rightmost “Advanced Events” column, unless the puzzle collapses earlier. In that case, the progress through basic solving is reported there.
Reviews of collections conclude with a “snapshot” post, giving solving highlights of the surveyed puzzles, and linking back to the earlier posts explaining the highlighted techniques.