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sav08:advanced_sat_solving_techniques [2008/03/13 10:43] vkuncak |
sav08:advanced_sat_solving_techniques [2008/03/13 10:49] vkuncak |
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| * head/tail list | * head/tail list | ||
| * two-literal watching: each var has list of unassigned literals, do search to see if there are other literals to watch in clause | * two-literal watching: each var has list of unassigned literals, do search to see if there are other literals to watch in clause | ||
| - | * invariant: each clause has at least one watched literal, but not all literals need to be watched | + | * invariant: each non-conflicting clause has at least one watched literal, but not all literals need to be watched |
| + | * no need to do anything on backtrack | ||
| Mechanisms other than unit propagation are less important: e.g. propagating equivalences. | Mechanisms other than unit propagation are less important: e.g. propagating equivalences. | ||
| Line 87: | Line 88: | ||
| If c1 is not asserting clause yet, we resolve it with antecedants of variables, following backwards deduction steps. | If c1 is not asserting clause yet, we resolve it with antecedants of variables, following backwards deduction steps. | ||
| + | |||
| + | In other words: we remove variables at current decision level until only one at the current is left. | ||
| The clause forces a different value of a decision variable at a previous level. | The clause forces a different value of a decision variable at a previous level. | ||