///<summary>
/// Finds the longest common subsequence in quadratic time and linear space
/// Variant of:
/// D. S. Hirschberg. A linear space algorithm for or computing maximal common subsequences. 1975.
/// http://dl.acm.org/citation.cfm?id=360861
/// </summary>
/// <returns>Number of pairs that were matched</returns>
public static int Match(ISymbolicExpressionTreeNode a, ISymbolicExpressionTreeNode b, ISymbolicExpressionTreeNodeSimilarityComparer comp) {
if (!comp.Equals(a, b)) return 0;
int m = a.SubtreeCount;
int n = b.SubtreeCount;
if (m == 0 || n == 0) return 1;
var matrix = new int[m + 1, n + 1];
for (int i = 1; i <= m; ++i) {
var ai = a.GetSubtree(i - 1);
for (int j = 1; j <= n; ++j) {
var bj = b.GetSubtree(j - 1);
int match = Match(ai, bj, comp);
matrix[i, j] = Math.Max(Math.Max(matrix[i, j - 1], matrix[i - 1, j]), matrix[i - 1, j - 1] + match);
}
}
return matrix[m, n] + 1;
}
public SymbolicExpressionTreeMaxCommonSubtreeSimilarityCalculatorTest()
{
comparer = new SymbolicExpressionTreeNodeEqualityComparer();
}
///<summary>
/// Finds the longest common subsequence in quadratic time and linear space
/// Variant of:
/// D. S. Hirschberg. A linear space algorithm for or computing maximal common subsequences. 1975.
/// http://dl.acm.org/citation.cfm?id=360861
/// </summary>
/// <returns>Number of pairs that were matched</returns>
public static int Match(ISymbolicExpressionTreeNode a, ISymbolicExpressionTreeNode b, ISymbolicExpressionTreeNodeSimilarityComparer comp)
{
if (!comp.Equals(a, b))
{
return(0);
}
int m = a.SubtreeCount;
int n = b.SubtreeCount;
if (m == 0 || n == 0)
{
return(1);
}
var matrix = new int[m + 1, n + 1];
for (int i = 1; i <= m; ++i)
{
var ai = a.GetSubtree(i - 1);
for (int j = 1; j <= n; ++j)
{
var bj = b.GetSubtree(j - 1);
int match = Match(ai, bj, comp);
matrix[i, j] = Math.Max(Math.Max(matrix[i, j - 1], matrix[i - 1, j]), matrix[i - 1, j - 1] + match);
}
}
return(matrix[m, n] + 1);
}
public static double MaxCommonSubtreeSimilarity(ISymbolicExpressionTree a, ISymbolicExpressionTree b, ISymbolicExpressionTreeNodeSimilarityComparer comparer)
{
int max = 0;
var rootA = a.Root.GetSubtree(0).GetSubtree(0);
var rootB = b.Root.GetSubtree(0).GetSubtree(0);
foreach (var aa in rootA.IterateNodesBreadth())
{
int lenA = aa.GetLength();
if (lenA <= max)
{
continue;
}
foreach (var bb in rootB.IterateNodesBreadth())
{
int lenB = bb.GetLength();
if (lenB <= max)
{
continue;
}
int matches = SymbolicExpressionTreeMatching.Match(aa, bb, comparer);
if (max < matches)
{
max = matches;
}
}
}
return(2.0 * max / (rootA.GetLength() + rootB.GetLength()));
}
public SymbolicExpressionTreeMaxCommonSubtreeSimilarityCalculatorTest() {
comparer = new SymbolicExpressionTreeNodeEqualityComparer();
}
public static double MaxCommonSubtreeSimilarity(ISymbolicExpressionTree a, ISymbolicExpressionTree b, ISymbolicExpressionTreeNodeSimilarityComparer comparer) {
int max = 0;
var rootA = a.Root.GetSubtree(0).GetSubtree(0);
var rootB = b.Root.GetSubtree(0).GetSubtree(0);
foreach (var aa in rootA.IterateNodesBreadth()) {
int lenA = aa.GetLength();
if (lenA <= max) continue;
foreach (var bb in rootB.IterateNodesBreadth()) {
int lenB = bb.GetLength();
if (lenB <= max) continue;
int matches = SymbolicExpressionTreeMatching.Match(aa, bb, comparer);
if (max < matches)
max = matches;
}
}
return 2.0 * max / (rootA.GetLength() + rootB.GetLength());
}
