/// <summary>
/// Returns the inner product of this vector with the specified vector.
/// </summary>
/// <param name="that">that the other vector</param>
/// <returns>the dot product between this vector and that vector</returns>
/// <exception cref="ArgumentException">if the lengths of the two vectors are not equal</exception>
public double Dot(SparseVector that)
{
if (_dims != that._dims)
{
throw new ArgumentException("Vector lengths disagree");
}
var sum = 0.0;
// iterate over the vector with the fewest nonzeros
if (_st.Size() <= that._st.Size())
{
foreach (int i in _st.Keys())
{
if (that._st.Contains(i))
{
sum += Get(i) * that.Get(i);
}
}
}
else
{
foreach (int i in that._st.Keys())
{
if (_st.Contains(i))
{
sum += Get(i) * that.Get(i);
}
}
}
return(sum);
}
/// <summary>
/// find a key with the highest frequency count
/// </summary>
public void SetMax()
{
_st.Put(_max, 0);
foreach (var word in _st.Keys())
{
if (_st.Get(word) == null)
{
continue;
}
if (_st.Get(word) > _st.Get(_max))
{
_max = word;
}
}
}