Subcritical process, adding clues “in field”

 

Subcritical process, adding clues “in field”

 

Entry is done in “subcritical mode” when some clues “in field” have to be added to reach the count.

 

Clues are added in the conditions described here after, then the “critical” mode is called.

Clues are added one by one, in recursive mode. As in each step one compulsory clue can disappear, at the end, we can enter the “critical mode” with a band 3 filled to 6 clues.

 

Clues can not be added in “critical stacks” ( a stack having 6 clues “given plus GUA2s GUA3s clues”).

The ‘in field” is reduced if possible for this specific task.

 

Solving a mini row

 

The general strategy is to solve in a step one mini row, adding one clue.

 

If the mini row has one GUA2, both cells are assigned, the mini row becomes empty for the future (and 2 clues are added to the stack.)

 

If the mini row has 3 GUA2s, the 3 cells are assigned the mini row becomes empty and 3 clues are added to the stack.

 

The 2 next cases (2 GUA2s in mini row or one GUA3 in mini row) are more complex but very similar.

 

In both cases, 2 cells are assigned out of three. The three possibility are tried; One isolate cell remains in the mini row.  This will be on more case for the next steps inside this “subcritical process”. 2 clues are added to the stack. The remaining cell is erased if the stack becomes critical.

 

The last case is to pick up the remaining cell. One clue is added to the stack

 

Selecting the next mini row to solve

 

Rows are processed in increasing order of the index. The first mini row not empty in a stack not “critical” is processed. As a consequence, if one cell is left in the mini row, it will be the next choice.

Within a mini row having some “in field” cells, only one of the five possibilities exists.

 

The process loop in recursive mode till the moment where the count out of GUA2s GUA3s is “critical”

When the “critical” mode is reached, the opening process of the critical mode is applied :

 

Solve mini rows having 2 GUA2s

Check the UAs A sub list

See if the global status leads to a multiple solution

Call the relevant “critical” process (new UAs check cycle of downstream process).