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Commit 6a97c5d9 authored by Kweku Adams's avatar Kweku Adams
Browse files

Improve replaceAll. 

The default implementation of Map.replaceAll() iterates through the
entrySet. Switch to a simple for loop iterating through the array
since the iterator is an inefficient way to access the array contents.

Benchmark results:

Before:

android.util.ArrayMapPerfTest#testReplaceAll_Large:
	replaceAll_Large_min (ns): 888977
	replaceAll_Large_median (ns): 904642
	replaceAll_Large_mean (ns): 914596
	replaceAll_Large_standardDeviation: 23960
android.util.ArrayMapPerfTest#testReplaceAll_Small:
	replaceAll_Small_min (ns): 177767
	replaceAll_Small_median (ns): 179955
	replaceAll_Small_mean (ns): 180331
	replaceAll_Small_standardDeviation: 2865

After:

android.util.ArrayMapPerfTest#testReplaceAll_Large:
	replaceAll_Large_min (ns): 557385
	replaceAll_Large_median (ns): 586495
	replaceAll_Large_mean (ns): 583712
	replaceAll_Large_standardDeviation: 20356
android.util.ArrayMapPerfTest#testReplaceAll_Small:
	replaceAll_Small_min (ns): 108051
	replaceAll_Small_median (ns): 110802
	replaceAll_Small_mean (ns): 109987
	replaceAll_Small_standardDeviation: 1334

Bug: 194098491
Test: atest CorePerfTests:ArrayMapPerfTest (see results above)
Test: atest CtsUtilTestCases:ArrayMapTest
Test: atest FrameworksCoreTests:ArrayMapTest
Change-Id: If87ae5f3aa4b184b95c16aed5f2fb6f31d11668a
parent da143d4a

apct-tests/perftests/core/src/android/util/ArrayMapPerfTest.java

+31 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ import org.junit.Test; 
import org.junit.runner.RunWith;



import java.util.function.BiConsumer;

import java.util.function.BiFunction;



@RunWith(AndroidJUnit4.class)

@LargeTest
@@ -69,4 +70,34 @@ public class ArrayMapPerfTest { 
            }

        }

    }



    @Test

    public void testReplaceAll_Small() {

        BenchmarkState state = mPerfStatusReporter.getBenchmarkState();

        BiFunction<Integer, Integer, Integer> function = (k, v) -> 2 * v;

        while (state.keepRunning()) {

            for (int i = 0; i < NUM_ITERATIONS; ++i) {

                ArrayMap<Integer, Integer> map = new ArrayMap<>();

                for (int j = 0; j < SET_SIZE_SMALL; j++) {

                    map.put(j, j);

                }

                map.replaceAll(function);

            }

        }

    }



    @Test

    public void testReplaceAll_Large() {

        BenchmarkState state = mPerfStatusReporter.getBenchmarkState();

        BiFunction<Integer, Integer, Integer> function = (k, v) -> 2 * v;

        while (state.keepRunning()) {

            for (int i = 0; i < NUM_ITERATIONS; ++i) {

                ArrayMap<Integer, Integer> map = new ArrayMap<>();

                for (int j = 0; j < SET_SIZE_LARGE; j++) {

                    map.put(j, j);

                }

                map.replaceAll(function);

            }

        }

    }

}

core/java/android/util/ArrayMap.java

+31 −0
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ import java.util.ConcurrentModificationException; 
import java.util.Map;

import java.util.Set;

import java.util.function.BiConsumer;

import java.util.function.BiFunction;



/**

 * ArrayMap is a generic key->value mapping data structure that is
@@ -1023,6 +1024,36 @@ public final class ArrayMap<K, V> implements Map<K, V> { 
        return MapCollections.removeAllHelper(this, collection);

    }



    /**

     * Replaces each entry's value with the result of invoking the given function on that entry

     * until all entries have been processed or the function throws an exception. Exceptions thrown

     * by the function are relayed to the caller. This implementation overrides

     * the default implementation to avoid iterating using the {@link #entrySet()} and iterates in

     * the key-value order consistent with {@link #keyAt(int)} and {@link #valueAt(int)}.

     *

     * @param function The function to apply to each entry

     */

    @Override

    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {

        if (function == null) {

            throw new NullPointerException("function must not be null");

        }



        final int size = mSize;

        try {

            for (int i = 0; i < size; ++i) {

                final int valIndex = (i << 1) + 1;

                //noinspection unchecked

                mArray[valIndex] = function.apply((K) mArray[i << 1], (V) mArray[valIndex]);

            }

        } catch (ArrayIndexOutOfBoundsException e) {

            throw new ConcurrentModificationException();

        }

        if (size != mSize) {

            throw new ConcurrentModificationException();

        }

    }



    /**

     * Remove all keys in the array map that do <b>not</b> exist in the given collection.

     * @param collection The collection whose contents are to be used to determine which