public static bool Collect <T, U>(INumberColumn <T> indices, IColumn <U> values, BitVector unusedValues) where T : unmanaged, IEquatable <T>
{
IRemapper <T> remapper = RemapperFactory.Build <T>();
// Trim indices first to consolidate references into a new consolidated array as much as possible
indices.Trim();
// Find all value indices which are no longer referenced by any row
indices.ForEach((slice) => remapper.RemoveValues(slice, unusedValues));
// If there are unused values, ...
int[] remapped = unusedValues.ToArray();
if (remapped.Length > 0)
{
int remapFrom = (values.Count - remapped.Length);
// Swap the *values* to the end of the values array
for (int i = 0; i < remapped.Length; ++i)
{
values.Swap(remapFrom + i, remapped[i]);
}
// Swap indices using those values to use the new ones
indices.ForEach((slice) => remapper.RemapAbove(slice, remapFrom, remapped));
// Remove the unused values that are now at the end of the array
values.RemoveFromEnd(remapped.Length);
}
// Trim values afterward to clean up any newly unused space
values.Trim();
// Return whether anything was remapped
return(remapped.Length > 0);
}
/// <summary>
/// FindUnusedAndCollect walks all values in the 'indices' column to find any indices with
/// no remaining references. It then swaps and removes them from the 'values' column and
/// updates indices in the 'indices' column to the updated values for all swapped rows.
///
/// This overload uses the provided BitVector to mark used rows. The caller can set BitVector
/// entries true to keep specific rows even if they aren't referenced in the indices column.
/// </summary>
/// <typeparam name="T">Type of index used (int or byte)</typeparam>
/// <param name="values">Column containing the values themselves</param>
/// <param name="indices">Column containing indices referring to rows in the values column</param>
/// <param name="rowsToKeep">BitVector to use to track referenced rows; values already set true will be kept even if unreferenced.</param>
/// <returns>True if any values were swapped and removed; false otherwise.</returns>
public static bool FindUnusedAndCollect <T>(IColumn values, INumberColumn <T> indices, BitVector rowsToKeep) where T : unmanaged, IEquatable <T>
{
IRemapper <T> remapper = RemapperFactory.Build <T>();
// Trim indices first to consolidate references into a new consolidated array as much as possible
indices.Trim();
// Find all value indices which are no longer referenced by any row
indices.ForEach((slice) => remapper.AddValues(slice, rowsToKeep));
return(Collect(values, new[] { indices }, rowsToKeep));
}