/// <summary>
/// Computes a mapping from the new species index to the old species index, or vice-versa.
/// </summary>
/// <param name="jCell">
/// Local cell index.
/// </param>
/// <param name="New2Old">
/// If true, a mapping from new species index to previous/old species index is returned,
/// if false the other way around.
/// </param>
/// <param name="LsTrk">
/// </param>
/// <returns>
/// Null, if there is no change in species ordering in cell <paramref name="jCell"/>
/// from the previous level-set tracker state to the actual.
///
/// Otherwise, if <paramref name="New2Old"/> is true, an array of the same length
/// as the number of species currently in cell <paramref name="jCell"/>.
/// - index: current species index in cell <paramref name="jCell"/>.
/// - content: index of this species with respect to the previous level-set-tracker state.
/// If <paramref name="New2Old"/> false, the other way around.
/// </returns>
public static int[] SpeciesUpdate(LevelSetTracker LsTrk, int jCell, bool New2Old)
{
ushort[] OldCode = LsTrk.RegionsHistory[0].RegionsCode;
ushort[] NewCode = LsTrk.RegionsHistory[1].RegionsCode;
// Only if the return value of this function is positive, a mapping from current species index to previous species index
// - index: current species index in cell <paramref name="jCell"/>.
// - content: index of this species with respect to the previous level-set-tracker state.
int[] UpdateMap = null;
bool AnyUpdate = false;
ushort oc = OldCode[jCell];
ushort nc = NewCode[jCell];
if (!New2Old)
{
// swap old and new
ushort b = oc;
oc = nc;
nc = b;
}
ReducedRegionCode oldRRC, newRRC;
int OldNoOfSpc = LsTrk.GetNoOfSpeciesByRegionCode(oc, out oldRRC);
int NewNoOfSpc = LsTrk.GetNoOfSpeciesByRegionCode(nc, out newRRC);
for (int new_iSpc = 0; new_iSpc < NewNoOfSpc; new_iSpc++)
{
SpeciesId spId = LsTrk.GetSpeciesIdFromIndex(newRRC, new_iSpc);
int old_iSpc = LsTrk.GetSpeciesIndex(oldRRC, spId); // if the species was not present in the previous state, this should be negative
if (old_iSpc != new_iSpc)
{
if (AnyUpdate == false)
{
// init the update map: no change up to index 'new_iSpc'
AnyUpdate = true;
UpdateMap = new int[NewNoOfSpc];
for (int i = 0; i < new_iSpc; i++)
{
UpdateMap[i] = i;
}
}
// index 'new_iSpc' maps to old species index
UpdateMap[new_iSpc] = old_iSpc;
}
}
if (NewNoOfSpc < OldNoOfSpc)
{
// the number of species is reduced - this also counts as change
if (AnyUpdate == false)
{
// init the update map: no change up to index 'new_iSpc'
AnyUpdate = true;
UpdateMap = new int[NewNoOfSpc];
for (int i = 0; i < NewNoOfSpc; i++)
{
UpdateMap[i] = i;
}
}
}
// return
return(UpdateMap);
}
