/// <summary>
/// Searches the entire curve based on a heuristic.
/// </summary>
/// <param name="heuristic">A heuristic that measures how close a value is to the target value. This heuristic should return 0 if the target value is a match.</param>
/// <returns>The position the search ended at if it was successful.</returns>
public static float?Search <TValue> (
this ICurve <TValue> curve,
CurveSearchHeuristic <TValue> heuristic
)
where TValue : struct
{
return(Search(curve, heuristic, curve.Start, curve.End));
}
/// <summary>
/// Searches a region of the curve based on a heuristic.
/// </summary>
/// <param name="heuristic">A heuristic that measures how close a value is to the target value. This heuristic should return 0 if the target value is a match.</param>
/// <param name="low">The beginning of the search window.</param>
/// <param name="high">The end of the search window.</param>
/// <param name="subdivision">The number of sample points within the search window. A higher number of partitions will increase the likelihood that the best match will be found by the search, but increase the cost of the search.</param>
/// <param name="maxRecursion">The maximum level of recursion for the search. High values for this argument will increase the precision of the search but also increase its cost.</param>
/// <returns>The position the search ended at if it was successful.</returns>
public static float?Search <TValue> (
this ICurve <TValue> curve,
CurveSearchHeuristic <TValue> heuristic, float low, float high,
int?subdivision = null, int?maxRecursion = null,
float?epsilon = null
)
where TValue : struct
{
float?result = null;
float bestScore = float.MaxValue;
SearchInternal(
curve,
heuristic,
low, high,
subdivision.GetValueOrDefault(DefaultSearchSubdivision),
maxRecursion.GetValueOrDefault(DefaultMaxSearchRecursion),
epsilon.GetValueOrDefault(DefaultSearchEpsilon),
ref result, ref bestScore,
0
);
return(result);
}
private static void SearchInternal <TValue> (
this ICurve <TValue> curve,
CurveSearchHeuristic <TValue> heuristic,
float low, float high,
int subdivision, int maxRecursion,
float epsilon,
ref float?bestScoringPosition, ref float bestScore,
int depth
)
where TValue : struct
{
if (subdivision < 2)
{
subdivision = 2;
}
if (high <= low)
{
return;
}
var actualSubdivision = subdivision;
if (depth == 0)
{
actualSubdivision = Math.Min(1024, curve.Count * 2);
actualSubdivision = Math.Max(actualSubdivision, subdivision);
}
bool improved = false;
float partitionSize = (high - low) / actualSubdivision, partitionSizeHalf = partitionSize * 0.5f;
if (Math.Abs(partitionSizeHalf) <= epsilon)
{
return;
}
for (int i = 0; i < actualSubdivision; i++)
{
var samplePosition = low + (partitionSize * i) + partitionSizeHalf;
var score = heuristic(samplePosition, curve.GetValueAtPosition(samplePosition));
if (score < bestScore)
{
bestScore = score;
bestScoringPosition = samplePosition;
improved = true;
}
}
if (depth >= maxRecursion)
{
return;
}
if (!improved)
{
return;
}
var newLow = Math.Max(low, bestScoringPosition.Value - partitionSizeHalf);
var newHigh = Math.Min(high, bestScoringPosition.Value + partitionSizeHalf);
SearchInternal(
curve,
heuristic,
newLow, newHigh,
subdivision, maxRecursion, epsilon,
ref bestScoringPosition, ref bestScore,
depth + 1
);
}
