private void MergeCascade(int level, T[] left, T[] right)
{
Contract.Requires(level > 0, "level");
Contract.Requires(left != null && left.Length == (1 << (level - 1)), "left");
Contract.Requires(right != null && right.Length == (1 << (level - 1)), "right");
if (IsFree(level))
{ // target level is empty
if (level >= m_levels.Length)
{
Grow(level);
}
Contract.Assert(level < m_levels.Length);
ColaStore.MergeSort(m_levels[level], left, right, m_comparer);
}
else if (IsFree(level + 1))
{ // the next level is empty
if (level + 1 >= m_levels.Length)
{
Grow(level + 1);
}
Contract.Assert(level + 1 < m_levels.Length);
var spare = GetSpare(level);
ColaStore.MergeSort(spare, left, right, m_comparer);
var next = m_levels[level];
ColaStore.MergeSort(m_levels[level + 1], next, spare, m_comparer);
Array.Clear(next, 0, next.Length);
PutSpare(level, spare);
}
else
{ // both are full, need to do a cascade merge
Contract.Assert(level < m_levels.Length);
// merge N and N +1
var spare = GetSpare(level);
ColaStore.MergeSort(spare, left, right, m_comparer);
// and cascade to N + 2 ...
var next = m_levels[level];
MergeCascade(level + 1, next, spare);
Array.Clear(next, 0, next.Length);
PutSpare(level, spare);
}
}
