From b1ccf74484f7400ebd6827fa6aa897b735f40d8e Mon Sep 17 00:00:00 2001
From: mwturvey <michael.w.turvey@intel.com>
Date: Mon, 13 Feb 2017 17:52:09 -0700
Subject: Optimize gradient descent for shallow valley

---
 tools/lighthousefind_tori/torus_localizer.c | 81 ++++++++++++++++++++++++++++-
 1 file changed, 79 insertions(+), 2 deletions(-)

(limited to 'tools')

diff --git a/tools/lighthousefind_tori/torus_localizer.c b/tools/lighthousefind_tori/torus_localizer.c
index 15177f2..b276e99 100644
--- a/tools/lighthousefind_tori/torus_localizer.c
+++ b/tools/lighthousefind_tori/torus_localizer.c
@@ -640,7 +640,7 @@ static Point RefineEstimateUsingGradientDescent(Point initialEstimate, PointsAnd
 
 	for (FLT f = startingPrecision; f > 0.0001; f *= descent)
 	{
-		Point gradient = getGradient(lastPoint, pna, pnaCount, f/1000 /*somewhat arbitrary*/);
+		Point gradient = getGradient(lastPoint, pna, pnaCount, f / 1000 /*somewhat arbitrary*/);
 		gradient = getNormalizedVector(gradient, f);
 
 		//printf("Gradient: (%f, %f, %f)\n", gradient.x, gradient.y, gradient.z);
@@ -679,6 +679,78 @@ static Point RefineEstimateUsingGradientDescent(Point initialEstimate, PointsAnd
 	return lastPoint;
 }
 
+// This is modifies the basic gradient descent algorithm to better handle the shallow valley case,
+// which appears to be typical of this convergence.  
+static Point RefineEstimateUsingModifiedGradientDescent1(Point initialEstimate, PointsAndAngle *pna, size_t pnaCount, FILE *logFile)
+{
+	int i = 0;
+	FLT lastMatchFitness = getPointFitness(initialEstimate, pna, pnaCount);
+	Point lastPoint = initialEstimate;
+	//Point lastGradient = getGradient(lastPoint, pna, pnaCount, .00000001 /*somewhat arbitrary*/);
+
+
+	for (FLT g = 0.1; g > 0.00001; g *= 0.99)
+	{
+		i++;
+		Point point1 = lastPoint;
+		// let's get 3 iterations of gradient descent here.
+		Point gradient1 = getGradient(point1, pna, pnaCount, g / 1000 /*somewhat arbitrary*/);
+		Point gradientN1 = getNormalizedVector(gradient1, g);
+
+		Point point2;
+		point2.x = point1.x + gradientN1.x;
+		point2.y = point1.y + gradientN1.y;
+		point2.z = point1.z + gradientN1.z;
+
+		Point gradient2 = getGradient(point2, pna, pnaCount, g / 1000 /*somewhat arbitrary*/);
+		Point gradientN2 = getNormalizedVector(gradient2, g);
+
+		Point point3;
+		point3.x = point2.x + gradientN2.x;
+		point3.y = point2.y + gradientN2.y;
+		point3.z = point2.z + gradientN2.z;
+
+		Point specialGradient = { .x = point3.x - point1.x, .y = point3.y - point1.y, .z = point3.y - point1.y };
+
+		specialGradient = getNormalizedVector(specialGradient, g/2);
+
+		Point point4;
+
+		point4.x = point3.x + specialGradient.x;
+		point4.y = point3.y + specialGradient.y;
+		point4.z = point3.z + specialGradient.z;
+
+		//point4.x = (point1.x + point2.x + point3.x) / 3;
+		//point4.y = (point1.y + point2.y + point3.y) / 3;
+		//point4.z = (point1.z + point2.z + point3.z) / 3;
+
+		FLT newMatchFitness = getPointFitness(point4, pna, pnaCount);
+
+		if (newMatchFitness > lastMatchFitness)
+		{
+			if (logFile)
+			{
+				writePoint(logFile, lastPoint.x, lastPoint.y, lastPoint.z, 0xFFFFFF);
+			}
+
+			lastMatchFitness = newMatchFitness;
+			lastPoint = point4;
+			printf("+");
+		}
+		else
+		{
+			printf("-");
+			g *= 0.7;
+
+		}
+
+
+	}
+	printf("\ni=%d\n", i);
+
+	return lastPoint;
+}
+
 Point SolveForLighthouse(TrackedObject *obj, char doLogOutput)
 {
 	PointsAndAngle pna[MAX_POINT_PAIRS];
@@ -714,7 +786,12 @@ Point SolveForLighthouse(TrackedObject *obj, char doLogOutput)
 
 	//Point refinedEstimatePc = RefineEstimateUsingPointCloud(initialEstimate, pna, pnaCount, obj, logFile);
 
-	Point refinedEstimageGd = RefineEstimateUsingGradientDescent(initialEstimate, pna, pnaCount, logFile, 0.95, 0.1);
+	//Point refinedEstimageGd = RefineEstimateUsingGradientDescent(initialEstimate, pna, pnaCount, logFile, 0.95, 0.1);
+
+	Point refinedEstimageGd = RefineEstimateUsingModifiedGradientDescent1(initialEstimate, pna, pnaCount, logFile);
+
+	//Point p = { .x = 8 };
+	//Point refinedEstimageGd = RefineEstimateUsingModifiedGradientDescent1(p, pna, pnaCount, logFile);
 
 	//FLT fitPc = getPointFitness(refinedEstimatePc, pna, pnaCount);
 	FLT fitGd = getPointFitness(refinedEstimageGd, pna, pnaCount);
-- 
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