This post finishes the review of Bernhard Hobinger’s Hodoku, with his Death Blossom page, featuring two insightful examples. The Sysudoku diagrams are followed by a summary of the site evaluations and Sysudoku lessons learned from this extensive site.
I began this review saying it would be an occasion to look back on the advanced methods illustrated in over four years of the Sysudoku blog. That has certainly been the case, with the Death Blossom a very suitable last look.
To quote from The ALS Petaled Death Blossom of July 2012:
“In this schematic of a death blossom, each candidate of a cell, the stem, sees all matching candidates in an ALS (including bv). The matching ALS, the petals, have at least one number in common among them. The ALS candidates of the common number form a toxic set.”
In the XYZ map scan, I suggest Death Blossom Lite(11/22/11), a version of the Death Blossom with bv petals, and came up with an three candidate stem in which the victim required a forcing chain to see all members of the toxic set.
Hodoku’s two examples of ALS Death Blossoms also illustrate that a stem of two or three candidates is about all you can expect. They also show that, compared to bv, ALS petals can generate more toxic set opportunities. In fact, a bv or triple with common linked ALS may be the most likely DB scenario. DB is another reason to scan for ALS. The stem cell can focus attention on two or three ALS among so many.
Here a stem of two candidates matches single candidates in a bv and a four cell ALS in a box. One victim sees all 6’s in both petals, a toxic set.
But sometimes, simpler is better.
The Hodoku Death Blossom candidates also form an AIC nice loop! This example shows how the ALS grouping and slink can form a nice loop, with more concentrated and powerful toxic sets.
The additional removals are especially welcome here, because the batting cage puzzle qualifies as a monster, if it has a solution.
Hodoku’s second example is also surprising, and in a very instructive way:
The three ALS are severely overlapped! It makes it easier for the victim to see the 5’s in all three, but is this legal? By Death Blossom logic, yes.
It’s all between the stem and petals. The victim sees all the fives, and if it is true, takes them all. Then each ALS takes its unique common candidate from the stem, leaving nothing . It doesn’t matter if commons overlap, as long as the petals covered by the victim include all candidates of the stem. Permitted overlap is another reason to consider Death Blossoms seriously in human solving.
Now to conclude the review with parting thoughts.
Regarding the Hodoku contribution to Sudoku solving, I believe it is primarily in the many excellent examples, to the extent readers can interpret them. Hobiger’s range of advanced puzzles is a superior achievement in itself. Perhaps I should have gotten into the batting cage for more Hodoku examples, but I fear your patience may not stretch any further.
However, while some techniques are adequately explained, Hodoku is not the place to discover why techniques work, or how or when, to spot them.
Anyone valuing their time must reject the Hodoku claim that productive chains are the product of arbitrary premises. For computers they are the result of millions of blind operations, premises included, with each chain starting with a premise related to the one among many searches that the software is currently on. For humans, chains must be the result of patient and knowledgeable chain construction, recognizing the construction goals and the chain results. Hodoku joins many other Sudoku writers in making the damaging error – or the intentional misrepresentation – of advising humans to mimic computer codes.
I began the review believing Berhard Hobiger had somehow devised Hodoku algorithms to create puzzles exhibiting advanced techniques on demand, by name, immediately after basic solving. Now I find that too hard to accept. Much more likely is that large numbers of puzzles were custom generated and filtered to derive a set for each demand category, ready for display when demanded. I’m not taking the time to confirm this suspicion. I could spend a lot more time to do that, and to solve delicious puzzles from the collections I have only sampled in review. But for now, that weekly deadline holds me to the next possible blog topic.
I feel that the effort that went into interpreting Bernhard Hobiger’s Hodoku site was well rewarded. It led to a satisfying review of my four-year blog, and pushed me in some new directions. I plan to continue for at least one more year. Then it may be time to limit my attention to refining the blog and making its contents more accessible. Unless, of course, something entirely new in human solving turns up!
Next, I return to Frank Longo with his compilation of Absolutely Nasty and Gordon Guide puzzles, which he deems The Nastiest Sudoku Book Ever. I’m sampling only from the last 100 of his 706 puzzles that “generally increase in difficulty,” hoping to recapture the spirit of his Absolutely Nasty IV reviewed earlier.
My 2016 plans include a revisit of the Bent N-Set family of methods. In the meantime I’m revisiting reviews of the toughest collections to update them according to the new position of this family in the revised Sysudoku Order of Battle(bar above).