add ext_backgroundtilt variabel (default=0 for backwards compatibilit…

…y) which compensates in-plane tilted backgrounds for calculating the bubble position. Add test which fails for the previous implementation that did not account for this. Thanks M. Mangold for signaling this issue.

engine/ext_bubblepos.go

@@ -9,10 +9,12 @@ var (
 	BubbleDist  = NewScalarValue("ext_bubbledist", "m", "Bubble traveled distance", bubbleDist)
 	BubbleSpeed = NewScalarValue("ext_bubblespeed", "m/s", "Bubble velocity", bubbleSpeed)
 	BubbleMz    = 1.0
+	BackGroundTilt    = 0.25
 )
 
 func init() {
 	DeclVar("ext_BubbleMz", &BubbleMz, "Center magnetization 1.0 or -1.0  (default = 1.0)")
+	DeclVar("ext_BackGroundTilt", &BackGroundTilt, "Size of in-plane component of background magnetization. All values below this one are rounded down to perfectly out-pf-plane to improve position calculation  (default = 0.25)")
 }
 
 func bubblePos() []float64 {
@@ -28,26 +30,26 @@ func bubblePos() []float64 {
 	}
 
 	{
-		var magsum float32
-		var weightedsum float32
+		var magsum float64
+		var weightedsum float64
 
 		for iy := range mz {
 			for ix := range mz[0] {
-				magsum += ((mz[iy][ix]*float32(BubbleMz) + 1.) / 2.)
-				weightedsum += ((mz[iy][ix]*float32(BubbleMz) + 1.) / 2.) * float32(iy)
+				magsum += (backgroundAdjust(mz[iy][ix]*float32(BubbleMz) + 1.) / 2.)
+				weightedsum += (backgroundAdjust(mz[iy][ix]*float32(BubbleMz) + 1.) / 2.) * float64(iy)
 			}
 		}
 		posy = float64(weightedsum / magsum)
 	}
 
 	{
-		var magsum float32
-		var weightedsum float32
+		var magsum float64
+		var weightedsum float64
 
 		for ix := range mz[0] {
 			for iy := range mz {
-				magsum += ((mz[iy][ix]*float32(BubbleMz) + 1.) / 2.)
-				weightedsum += ((mz[iy][ix]*float32(BubbleMz) + 1.) / 2.) * float32(ix)
+				magsum += (backgroundAdjust(mz[iy][ix]*float32(BubbleMz) + 1.) / 2.)
+				weightedsum += (backgroundAdjust(mz[iy][ix]*float32(BubbleMz) + 1.) / 2.) * float64(ix)
 			}
 		}
 		posx = float64(weightedsum / magsum)
@@ -112,3 +114,8 @@ func bubbleSpeed() float64 {
 
 	return v
 }
+
+func backgroundAdjust(arg float32) float64{
+if float64(arg)< BackGroundTilt{
+return float64(0)}
+return float64(arg)}

test/bubblepos.mx3

@@ -0,0 +1,28 @@
+SetMesh(128, 128, 1, 1e-9,1e-9,0.4e-9, 1, 0, 0)
+
+Msat  =580e3
+Aex   = 15e-12
+enabledemag=true
+alpha = 0.1
+Ku1=0.59e6+4*pi*1e-7*0.5*580e3*580e3
+anisU=vector(0,0,1)
+Dind=0.0034089785
+
+shiftregions=false
+
+m =neelskyrmion(1, -1).transl(-30e-9,0e-9,0)
+minimize()
+
+
+ext_bubbleMz = -1.0
+//without compensating for in-plane tilts of the background this fails (corresponds to ext_backgroundtilt=0)
+ext_backgroundtilt=0.25 //default value
+
+TOL:=1e-9
+expectv("position", ext_bubblepos.average(), vector(-3e-08,0,0), TOL)
+
+
+SetMesh(128, 128, 1, 1e-9,1e-9,0.4e-9, 0, 1, 0)
+m =neelskyrmion(1, -1).transl(0e-9,-30e-9,0)
+minimize()
+expectv("position", ext_bubblepos.average(), vector(0,-3e-08,0), TOL)