In constraint satisfaction, backmarking is a variant of the backtracking algorithm.

was instantiated to a value and information about what changed since then. In particular:

1. was then inconsistent;

2. of a variable that was changed since then.

, etc.

The second information is changed every time another.

, then:

1. is still inconsistent as it was before, as none of these variables changed so far; as a result, no further consistency check is necessary;

2. may still be inconsistent.

Contrary to other variants to backtracking, backmarking does not reduce the search space but only possibly reduce the number of constraints that are satisfied by a partial solution.

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