Switch from FloatMath -> Math and Math.hypot where possible

The motivation is an API change: FloatMath is going to be
deprecated and/or removed. Performance is not the goal of
this change.

That said...

Math is faster than FloatMath with AOT compilation.

While making the change, occurances of:

{Float}Math.sqrt(x * x + y * y) and
{Float}Math.sqrt({Float}Math.pow(x, 2) + {Float}Math.pow(y, 2))

have been replaced with:

{(float)} Math.hypot(x, y)

Right now there is no runtime intrinsic for hypot so is not faster
in all cases for AOT compilation:

Math.sqrt(x * x + y * y) is faster than Math.hypot(x, y) with
AOT, but all other combinations of FloatMath, use of pow() etc.
are slower than hypot().

hypot() has the advantage of being self documenting and
could be optimized in future. None of the behavior differences
around NaN and rounding appear to be important for the cases
looked at: they all assume results and arguments are in range
and usually the results are cast to float.

Different implementations measured on hammerhead / L:

AOT compiled:

[FloatMath.hypot(x, y)]
benchmark=Hypot_FloatMathHypot} 633.85 ns; σ=0.32 ns @ 3 trials

[FloatMath.sqrt(x*x + y*y)]
benchmark=Hypot_FloatMathSqrtMult} 684.17 ns; σ=4.83 ns @ 3 trials

[FloatMath.sqrt(FloatMath.pow(x, 2) + FloatMath.pow(y, 2))]
benchmark=Hypot_FloatMathSqrtPow} 1270.65 ns; σ=12.20 ns @ 6 trials

[(float) Math.hypot(x, y)]
benchmark=Hypot_MathHypot} 96.80 ns; σ=0.05 ns @ 3 trials

[(float) Math.sqrt(x*x + y*y)]
benchmark=Hypot_MathSqrtMult} 23.97 ns; σ=0.01 ns @ 3 trials

[(float) Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2))]
benchmark=Hypot_MathSqrtPow} 156.19 ns; σ=0.12 ns @ 3 trials

Interpreter:

benchmark=Hypot_FloatMathHypot} 1180.54 ns; σ=5.13 ns @ 3 trials
benchmark=Hypot_FloatMathSqrtMult} 1121.05 ns; σ=3.80 ns @ 3 trials
benchmark=Hypot_FloatMathSqrtPow} 3327.14 ns; σ=7.33 ns @ 3 trials
benchmark=Hypot_MathHypot} 856.57 ns; σ=1.41 ns @ 3 trials
benchmark=Hypot_MathSqrtMult} 1028.92 ns; σ=9.11 ns @ 3 trials
benchmark=Hypot_MathSqrtPow} 2539.47 ns; σ=24.44 ns @ 3 trials

Bug: https://code.google.com/p/android/issues/detail?id=36199
Change-Id: I06c91f682095e627cb547d60d936ef87941be692

3 files changed, 6 insertions, 7 deletions

diff --git a/core/java/android/gesture/GestureOverlayView.java b/core/java/android/gesture/GestureOverlayView.java
index 2d47f28..e0bb6e0 100644
--- a/core/java/android/gesture/GestureOverlayView.java
+++ b/core/java/android/gesture/GestureOverlayView.java
@@ -635,7 +635,7 @@ public class GestureOverlayView extends FrameLayout {
             mStrokeBuffer.add(new GesturePoint(x, y, event.getEventTime()));
 
             if (mHandleGestureActions && !mIsGesturing) {
-                mTotalLength += (float) Math.sqrt(dx * dx + dy * dy);
+                mTotalLength += (float) Math.hypot(dx, dy);
 
                 if (mTotalLength > mGestureStrokeLengthThreshold) {
                     final OrientedBoundingBox box =
diff --git a/core/java/android/gesture/GestureStroke.java b/core/java/android/gesture/GestureStroke.java
index 1d0f0fe..bed904e 100644
--- a/core/java/android/gesture/GestureStroke.java
+++ b/core/java/android/gesture/GestureStroke.java
@@ -69,8 +69,7 @@ public class GestureStroke {
                 bx.bottom = p.y;
                 len = 0;
             } else {
-                len += Math.sqrt(Math.pow(p.x - tmpPoints[(i - 1) * 2], 2)
-                        + Math.pow(p.y - tmpPoints[(i -1 ) * 2 + 1], 2));
+                len += Math.hypot(p.x - tmpPoints[(i - 1) * 2], p.y - tmpPoints[(i -1 ) * 2 + 1]);
                 bx.union(p.x, p.y);
             }
             index++;
diff --git a/core/java/android/gesture/GestureUtils.java b/core/java/android/gesture/GestureUtils.java
index dd221fc..416279e 100644
--- a/core/java/android/gesture/GestureUtils.java
+++ b/core/java/android/gesture/GestureUtils.java
@@ -293,7 +293,7 @@ public final class GestureUtils {
             }
             float deltaX = currentPointX - lstPointX;
             float deltaY = currentPointY - lstPointY;
-            float distance = (float) Math.sqrt(deltaX * deltaX + deltaY * deltaY);
+            float distance = (float) Math.hypot(deltaX, deltaY);
             if (distanceSoFar + distance >= increment) {
                 float ratio = (increment - distanceSoFar) / distance;
                 float nx = lstPointX + ratio * deltaX;
@@ -379,7 +379,7 @@ public final class GestureUtils {
         for (int i = 0; i < count; i += 2) {
             float dx = points[i + 2] - points[i];
             float dy = points[i + 3] - points[i + 1];
-            sum += Math.sqrt(dx * dx + dy * dy);
+            sum += Math.hypot(dx, dy);
         }
         return sum;
     }
@@ -388,13 +388,13 @@ public final class GestureUtils {
         float totalLen = computeTotalLength(points);
         float dx = points[2] - points[0];
         float dy = points[3] - points[1];
-        return (float) Math.sqrt(dx * dx + dy * dy) / totalLen;
+        return (float) Math.hypot(dx, dy) / totalLen;
     }
 
     static float computeStraightness(float[] points, float totalLen) {
         float dx = points[2] - points[0];
         float dy = points[3] - points[1];
-        return (float) Math.sqrt(dx * dx + dy * dy) / totalLen;
+        return (float) Math.hypot(dx, dy) / totalLen;
     }
 
     /**