/// <summary>
/// Computes the longest common subsequence matrix between the two collections
/// </summary>
/// <param name="first"></param>
/// <param name="second"></param>
private double LCS(ref IDiffObjectsCollection first, ref IDiffObjectsCollection second)
{
int start = 0;
int firstEnd = first.Count;
int secondEnd = second.Count;
int i, j, n, m;
IDiffObjectsCollection granularDiffsForFirst = null;
IDiffObjectsCollection granularDiffsForSecond = null;
IDiffObjectsCollection granularCommonElements = null;
IDiffObjectsCollection currCommonElements = first.CommonElements;
second.CommonElements = currCommonElements;
//trim the matching items at the beggining
while (start < firstEnd && start < secondEnd && first[start].ValueMatches(second[start], out granularDiffsForFirst, out granularDiffsForSecond, out granularCommonElements))
{
//if the collections were slightly different add the small differences
first.Differences.AddRange(granularDiffsForFirst);
second.Differences.AddRange(granularDiffsForSecond);
if (granularDiffsForFirst == null && granularDiffsForSecond == null)
{
currCommonElements.Add(first[start]);
}
else
{
currCommonElements.AddRange(granularCommonElements);
}
start++;
}
//trim the matching items at the end
while (firstEnd > start && secondEnd > start && first[firstEnd - 1].ValueMatches(second[secondEnd - 1], out granularDiffsForFirst, out granularDiffsForSecond, out granularCommonElements))
{
firstEnd--;
secondEnd--;
if (granularDiffsForFirst == null && granularDiffsForSecond == null)
{
currCommonElements.Add(first[firstEnd]);
}
else
{
currCommonElements.AddRange(granularCommonElements);
}
//if the collections were slightly different insert the small differences
first.Differences.PushRange(granularDiffsForFirst);
second.Differences.PushRange(granularDiffsForSecond);
}
m = firstEnd - start + 1;
n = secondEnd - start + 1;
//truncate the matrix to prevent OOM
m = Math.Min(m, MAX_MATRIX_LENGTH);
n = Math.Min(n, MAX_MATRIX_LENGTH);
//create the matrix for LCS
ushort[,] C = new ushort[m, n];
for (i = 1; i < m; i++)
{
for (j = 1; j < n; j++)
{
if (first[start + i - 1].ValueMatches(second[start + j - 1]))
{
C[i, j] = (ushort)(C[i - 1, j - 1] + 1);
}
else
{
C[i, j] = Math.Max(C[i, j - 1], C[i - 1, j]);
}
}
}
//populate the differences
return(ExtractDiffs(C, first, second, start, m, n));
}
public double Diff(ref IDiffObjectsCollection first, ref IDiffObjectsCollection second)
{
int i = 0, j = 0, m = first.Count, n = second.Count;
double diffCount1 = 0;
double diffCount2 = 0;
IDiffObjectsCollection granularDiffs1 = null;
IDiffObjectsCollection granularDiffs2 = null;
IDiffObjectsCollection granularCommon = null;
IDiffObjectsCollection currCommonElements = first.CommonElements;
second.CommonElements = currCommonElements;
while (i < m || j < n)
{
if (j < n && i < m && first[i].ValueMatches(second[j], out granularDiffs1, out granularDiffs2, out granularCommon))
{
first.Differences.AddRange(granularDiffs1);
second.Differences.AddRange(granularDiffs2);
if (granularDiffs1 == null && granularDiffs2 == null)
{
currCommonElements.Add(first[i]);
}
else
{
currCommonElements.AddRange(granularCommon);
}
i++;
j++;
}
else if (i < m && (j >= n || first[i].CompareValues(second[j], _ignoreCase) == CompareResult.Lower))
{
first.Differences.Add(first[i]);
diffCount1++;
i++;
}
else if (j < n && (i >= m || first[i].CompareValues(second[j], _ignoreCase) == CompareResult.Greater))
{
second.Differences.Add(second[j]);
diffCount2++;
j++;
}
}
//calculate diff ratio, or similarity factor
double ratio1 = 0;
if (first.Count > 0)
{
ratio1 = 1 - diffCount1 / first.Count;
}
double ratio2 = 0;
if (second.Count > 0)
{
ratio2 = 1 - diffCount2 / second.Count;
}
return(Math.Min(ratio1, ratio2));
}
private double ExtractDiffs(
ushort[, ] C, IDiffObjectsCollection first, IDiffObjectsCollection second, int start, int m, int n)
{
int i = m - 1, j = n - 1;
double diffCount1 = 0;
double diffCount2 = 0;
IDiffObjectsCollection currFirstDiffs = first.Differences;
IDiffObjectsCollection currSecondDiffs = second.Differences;
IDiffObjectsCollection currCommonElements = first.CommonElements;
second.CommonElements = currCommonElements;
do
{
int iIndex = start + i - 1;
int jIndex = start + j - 1;
IDiffObject currFirst = null;
IDiffObject currSecond = null;
IDiffObjectsCollection granularDiffsForFirst = null;
IDiffObjectsCollection granularDiffsForSecond = null;
IDiffObjectsCollection granularCommonElements = null;
if (iIndex >= 0 && iIndex < first.Count)
{
currFirst = first[iIndex];
}
if (jIndex >= 0 && jIndex < second.Count)
{
currSecond = second[jIndex];
}
if (currFirst != null &&
currFirst.ValueMatches(currSecond, out granularDiffsForFirst, out granularDiffsForSecond, out granularCommonElements))
{
//ValuesMatch can return true if the objects are very similar
//In that case we need to capture granular differences
currFirstDiffs.PushRange(granularDiffsForFirst);
currSecondDiffs.PushRange(granularDiffsForSecond);
if (granularDiffsForFirst == null && granularDiffsForSecond == null)
{
currCommonElements.Add(currFirst);
}
else
{
currCommonElements.AddRange(granularCommonElements);
}
i--; j--;
}
else if (j > 0 && (i <= 0 || C[i, j - 1] >= C[i - 1, j]))
{
currSecondDiffs.Push(currSecond);
diffCount2++;
j--;
}
else if (i > 0 && (j <= 0 || C[i, j - 1] < C[i - 1, j]))
{
currFirstDiffs.Push(currFirst);
diffCount1++;
i--;
}
}while (i > 0 || j > 0);
//calculate diff ratio, or similarity factor
double ratio1 = 0;
if (first.Count > 0)
{
ratio1 = 1 - diffCount1 / first.Count;
}
double ratio2 = 0;
if (second.Count > 0)
{
ratio2 = 1 - diffCount2 / second.Count;
}
return(Math.Min(ratio1, ratio2));
}
