Coverage RemoveSubsets(Coverage groups)
{
var not_subsets = new Coverage();
foreach (var candidate_subset in groups)
{
if (!groups.Any(candidate_superset => candidate_subset.IsProperSubsetOf(candidate_superset)))
{
not_subsets.Add(candidate_subset);
}
}
return(not_subsets);
}
public static string ToSOPExpression(this Coverage coverage)
{
var result = new StringBuilder();
var groups = coverage.OrderBy(g => g.Count).ToList();
for (int g = 0; g < groups.Count; g++)
{
result.Append(groups[g].ToMintermExpression());
if (g != (groups.Count - 1))
{
result.Append(" + ");
}
}
return(result.ToString());
}
Coverage MergeGroups(Coverage groups)
{
var merged = new Coverage();
foreach (var g1 in groups)
{
foreach (var g2 in groups)
{
// Two groups can only merge if they are adjacent and disjoint
if (g1.Intersect(g2).Count() == 0 && AreGroupsAdjacent(g1, g2))
{
var new_group = new Group(g1.Union(g2));
merged.Add(new_group);
}
}
}
return(new Coverage(groups.Union(merged)));
}
public HashSet <Coverage> Minimize()
{
var groups = new Coverage();
// Generate initial groups (of cardinality 1)
foreach (var one in on_set_binary)
{
groups.Add(new Group()
{
one
});
}
// onsider the don't cares as 'ones', but don't consider them essential
foreach (var dc in dc_set_binary)
{
groups.Add(new Group()
{
dc
});
}
Coverage previous_groups = null;
// Continue merging and optimizing until it's possible
while (previous_groups == null || !groups.Equals(previous_groups))
{
previous_groups = groups; // Save the state before merging and optimizing
// Merge groups of cardinality 'n' to create groups of double cardinality
groups = MergeGroups(groups);
// Clean up groups that are strict subsets of other groups
groups = RemoveSubsets(groups);
}
// Detect essential groups
groups = MarkEssential(groups);
// Remove completely redundant groups, that is, groups that cover 'ones' (of the function) already covered by other ESSENTIAL groups
groups = RemoveRedundant(groups);
return(GetCoverages(groups));
}
bool IsValidCoverage(Coverage selected_groups, out Coverage coverage)
{
coverage = null;
var on_set = new SortedSet <string>(on_set_binary);
foreach (var g in selected_groups)
{
on_set.ExceptWith(g);
}
// A coverage is valid if and only if it covers all the 'ones' of the function
if (on_set.Any())
{
return(false);
}
else
{
coverage = new Coverage(selected_groups)
{
Cost = CoverageCost(selected_groups)
};
return(true);
}
}