From 33253a4baa6279f81a73425b49dfb6abe5f5416e Mon Sep 17 00:00:00 2001
From: Neil Fuller <nfuller@google.com>
Date: Wed, 1 Oct 2014 11:55:10 +0100
Subject: Switch from FloatMath -> Math and Math.hypot where possible
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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
---
 .../android/internal/policy/impl/WindowOrientationListener.java    | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

(limited to 'policy')

diff --git a/policy/src/com/android/internal/policy/impl/WindowOrientationListener.java b/policy/src/com/android/internal/policy/impl/WindowOrientationListener.java
index 0c77556..d927592 100644
--- a/policy/src/com/android/internal/policy/impl/WindowOrientationListener.java
+++ b/policy/src/com/android/internal/policy/impl/WindowOrientationListener.java
@@ -23,7 +23,6 @@ import android.hardware.SensorEventListener;
 import android.hardware.SensorManager;
 import android.os.Handler;
 import android.os.SystemProperties;
-import android.util.FloatMath;
 import android.util.Log;
 import android.util.Slog;
 
@@ -401,7 +400,7 @@ public abstract class WindowOrientationListener {
                 if (LOG) {
                     Slog.v(TAG, "Raw acceleration vector: "
                             + "x=" + x + ", y=" + y + ", z=" + z
-                            + ", magnitude=" + FloatMath.sqrt(x * x + y * y + z * z));
+                            + ", magnitude=" + Math.sqrt(x * x + y * y + z * z));
                 }
 
                 // Apply a low-pass filter to the acceleration up vector in cartesian space.
@@ -428,7 +427,7 @@ public abstract class WindowOrientationListener {
                     if (LOG) {
                         Slog.v(TAG, "Filtered acceleration vector: "
                                 + "x=" + x + ", y=" + y + ", z=" + z
-                                + ", magnitude=" + FloatMath.sqrt(x * x + y * y + z * z));
+                                + ", magnitude=" + Math.sqrt(x * x + y * y + z * z));
                     }
                     skipSample = false;
                 }
@@ -442,7 +441,7 @@ public abstract class WindowOrientationListener {
                 boolean isSwinging = false;
                 if (!skipSample) {
                     // Calculate the magnitude of the acceleration vector.
-                    final float magnitude = FloatMath.sqrt(x * x + y * y + z * z);
+                    final float magnitude = (float) Math.sqrt(x * x + y * y + z * z);
                     if (magnitude < NEAR_ZERO_MAGNITUDE) {
                         if (LOG) {
                             Slog.v(TAG, "Ignoring sensor data, magnitude too close to zero.");
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