RonK wrote:You make it sound as if the "extra power" comes from the ALS. That is just not true. The extra power comes from the continuous loop. Your example is a continuous loop even with r7c1 and r6c1 treated separately.

- r2c1 -9- r1c5 -3- r7c5 -1- r7c1 -5- r6c1 -3- r2c1 - continuous loop

PIsaacson wrote:Being a devotee of ALS chains, I would have said, "The extra power comes from the continuous loop as well as the dual-linked ALS chain.OWTTE

From another angle, dual linked ALS and continuous loops share a common property, which might be considered the source of such extra power.

Any group of cells, or other strong sets, whose candidates can be contained in an equal number of links will eliminate all other candidates residing in the links. Here "link" is used in the general sense to mean sharing the same house or cell.

This is a general property that can be applied to all logical Sudoku solving methods.

One example might be this simple mixture of ALS with other logic here.