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Commit 33253a4b authored by Neil Fuller's avatar Neil Fuller
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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
parent 04517286

core/java/android/gesture/GestureOverlayView.java

+1 −1
Original line number Diff line number Diff line
@@ -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 =

core/java/android/gesture/GestureStroke.java

+1 −2
Original line number Diff line number Diff line
@@ -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++;

core/java/android/gesture/GestureUtils.java

+4 −4
Original line number Diff line number Diff line
@@ -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;

    }



    /**

core/java/android/hardware/GeomagneticField.java

+1 −1
Original line number Diff line number Diff line
@@ -281,7 +281,7 @@ public class GeomagneticField { 
     * @return  Horizontal component of the field strength in nonoteslas.

     */

    public float getHorizontalStrength() {

        return (float) Math.sqrt(mX * mX + mY * mY);

        return (float) Math.hypot(mX, mY);

    }



    /**

core/java/android/text/BoringLayout.java

+2 −3
Original line number Diff line number Diff line
@@ -20,7 +20,6 @@ import android.graphics.Canvas; 
import android.graphics.Paint;

import android.graphics.Path;

import android.text.style.ParagraphStyle;

import android.util.FloatMath;



/**

 * A BoringLayout is a very simple Layout implementation for text that
@@ -211,7 +210,7 @@ public class BoringLayout extends Layout implements TextUtils.EllipsizeCallback 
            TextLine line = TextLine.obtain();

            line.set(paint, source, 0, source.length(), Layout.DIR_LEFT_TO_RIGHT,

                    Layout.DIRS_ALL_LEFT_TO_RIGHT, false, null);

            mMax = (int) FloatMath.ceil(line.metrics(null));

            mMax = (int) Math.ceil(line.metrics(null));

            TextLine.recycle(line);

        }
@@ -305,7 +304,7 @@ public class BoringLayout extends Layout implements TextUtils.EllipsizeCallback 
            TextLine line = TextLine.obtain();

            line.set(paint, text, 0, length, Layout.DIR_LEFT_TO_RIGHT,

                    Layout.DIRS_ALL_LEFT_TO_RIGHT, false, null);

            fm.width = (int) FloatMath.ceil(line.metrics(fm));

            fm.width = (int) Math.ceil(line.metrics(fm));

            TextLine.recycle(line);



            return fm;