/// <summary>
/// Subtracts another vector to this vector and stores the result into the result vector.
/// </summary>
/// <param name="other">
/// The vector to subtract from this one.
/// </param>
/// <param name="result">
/// The vector to store the result of the subtraction.
/// </param>
protected override void DoSubtract(Vector <double> other, Vector <double> result)
{
if (ReferenceEquals(this, other))
{
result.Clear();
return;
}
var otherSparse = other as SparseVector;
if (otherSparse == null)
{
base.DoSubtract(other, result);
return;
}
var resultSparse = result as SparseVector;
if (resultSparse == null)
{
base.DoSubtract(other, result);
return;
}
// TODO (ruegg, 2011-10-11): Options to optimize?
var otherStorage = otherSparse._storage;
if (ReferenceEquals(this, resultSparse))
{
int i = 0, j = 0;
while (j < otherStorage.ValueCount)
{
if (i >= _storage.ValueCount || _storage.Indices[i] > otherStorage.Indices[j])
{
var otherValue = otherStorage.Values[j];
if (otherValue != 0.0)
{
_storage.InsertAtIndexUnchecked(i++, otherStorage.Indices[j], -otherValue);
}
j++;
}
else if (_storage.Indices[i] == otherStorage.Indices[j])
{
// TODO: result can be zero, remove?
_storage.Values[i++] -= otherStorage.Values[j++];
}
else
{
i++;
}
}
}
else
{
result.Clear();
int i = 0, j = 0, last = -1;
while (i < _storage.ValueCount || j < otherStorage.ValueCount)
{
if (j >= otherStorage.ValueCount || i < _storage.ValueCount && _storage.Indices[i] <= otherStorage.Indices[j])
{
var next = _storage.Indices[i];
if (next != last)
{
last = next;
result.At(next, _storage.Values[i] - otherSparse.At(next));
}
i++;
}
else
{
var next = otherStorage.Indices[j];
if (next != last)
{
last = next;
result.At(next, At(next) - otherStorage.Values[j]);
}
j++;
}
}
}
}
