util/HashMap/WhiteBoxResizeTest.java

/*
 * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

import org.testng.annotations.Test;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.invoke.VarHandle;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.IntStream;

import static java.util.stream.Collectors.toMap;
import static org.testng.Assert.assertEquals;
import static org.testng.Assert.assertNull;

/*
 * @test
 * @bug 8210280
 * @modules java.base/java.util:open
 * @summary White box tests for HashMap internals around table resize
 * @run testng WhiteBoxResizeTest
 */
public class WhiteBoxResizeTest {
    final MethodHandle TABLE_SIZE_FOR;
    final VarHandle THRESHOLD;
    final VarHandle TABLE;

    public WhiteBoxResizeTest() throws ReflectiveOperationException {
        Class<?> mClass = HashMap.class;
        String nodeClassName = mClass.getName() + "$Node";
        Class<?> nodeArrayClass = Class.forName("[L" + nodeClassName + ";");
        MethodHandles.Lookup lookup = MethodHandles.privateLookupIn(mClass, MethodHandles.lookup());
        TABLE = lookup.findVarHandle(mClass, "table", nodeArrayClass);
        this.TABLE_SIZE_FOR = lookup.findStatic(
                mClass, "tableSizeFor",
                MethodType.methodType(int.class, int.class));
        this.THRESHOLD = lookup.findVarHandle(mClass, "threshold", int.class);
    }

    int tableSizeFor(int n) {
        try {
            return (int) TABLE_SIZE_FOR.invoke(n);
        } catch (Throwable t) { throw new AssertionError(t); }
    }

    Object[] table(HashMap map) {
        try {
            return (Object[]) TABLE.get(map);
        } catch (Throwable t) { throw new AssertionError(t); }
    }

    int capacity(HashMap map) {
        return table(map).length;
    }

    @Test
    public void testTableSizeFor() {
        assertEquals(tableSizeFor(0), 1);
        assertEquals(tableSizeFor(1), 1);
        assertEquals(tableSizeFor(2), 2);
        assertEquals(tableSizeFor(3), 4);
        assertEquals(tableSizeFor(15), 16);
        assertEquals(tableSizeFor(16), 16);
        assertEquals(tableSizeFor(17), 32);
        int maxSize = 1 << 30;
        assertEquals(tableSizeFor(maxSize - 1), maxSize);
        assertEquals(tableSizeFor(maxSize), maxSize);
        assertEquals(tableSizeFor(maxSize + 1), maxSize);
        assertEquals(tableSizeFor(Integer.MAX_VALUE), maxSize);
    }

    @Test
    public void capacityTest() {
        HashMap<Integer, Integer> map = new HashMap<>();
        assertNull(table(map));

        map.put(1, 1);
        assertEquals(capacity(map), 16);

        map.putAll(IntStream.range(0, 64).boxed().collect(toMap(i -> i, i -> i)));
        assertEquals(capacity(map), 128);
    }
}
Revision:	1.1
Committed:	Tue Dec 18 20:21:24 2018 UTC (5 years, 5 months ago) by jsr166
Branch:	MAIN
Log Message:	8210280: Unnecessary reallocation when invoking HashMap.putAll()
#	User	Rev	Content
1	jsr166	1.1	/*
2			* Copyright (c) 2018, Red Hat, Inc. All rights reserved.
3			*
4			* This code is free software; you can redistribute it and/or modify it
5			* under the terms of the GNU General Public License version 2 only, as
6			* published by the Free Software Foundation.
7			*
8			* This code is distributed in the hope that it will be useful, but WITHOUT
9			* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10			* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11			* version 2 for more details (a copy is included in the LICENSE file that
12			* accompanied this code).
13			*
14			* You should have received a copy of the GNU General Public License version
15			* 2 along with this work; if not, write to the Free Software Foundation,
16			* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17			*
18			* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19			* or visit www.oracle.com if you need additional information or have any
20			* questions.
21			*/
22
23			import org.testng.annotations.Test;
24
25			import java.lang.invoke.MethodHandle;
26			import java.lang.invoke.MethodHandles;
27			import java.lang.invoke.MethodType;
28			import java.lang.invoke.VarHandle;
29			import java.util.HashMap;
30			import java.util.Map;
31			import java.util.stream.IntStream;
32
33			import static java.util.stream.Collectors.toMap;
34			import static org.testng.Assert.assertEquals;
35			import static org.testng.Assert.assertNull;
36
37			/*
38			* @test
39			* @bug 8210280
40			* @modules java.base/java.util:open
41			* @summary White box tests for HashMap internals around table resize
42			* @run testng WhiteBoxResizeTest
43			*/
44			public class WhiteBoxResizeTest {
45			final MethodHandle TABLE_SIZE_FOR;
46			final VarHandle THRESHOLD;
47			final VarHandle TABLE;
48
49			public WhiteBoxResizeTest() throws ReflectiveOperationException {
50			Class<?> mClass = HashMap.class;
51			String nodeClassName = mClass.getName() + "$Node";
52			Class<?> nodeArrayClass = Class.forName("[L" + nodeClassName + ";");
53			MethodHandles.Lookup lookup = MethodHandles.privateLookupIn(mClass, MethodHandles.lookup());
54			TABLE = lookup.findVarHandle(mClass, "table", nodeArrayClass);
55			this.TABLE_SIZE_FOR = lookup.findStatic(
56			mClass, "tableSizeFor",
57			MethodType.methodType(int.class, int.class));
58			this.THRESHOLD = lookup.findVarHandle(mClass, "threshold", int.class);
59			}
60
61			int tableSizeFor(int n) {
62			try {
63			return (int) TABLE_SIZE_FOR.invoke(n);
64			} catch (Throwable t) { throw new AssertionError(t); }
65			}
66
67			Object[] table(HashMap map) {
68			try {
69			return (Object[]) TABLE.get(map);
70			} catch (Throwable t) { throw new AssertionError(t); }
71			}
72
73			int capacity(HashMap map) {
74			return table(map).length;
75			}
76
77			@Test
78			public void testTableSizeFor() {
79			assertEquals(tableSizeFor(0), 1);
80			assertEquals(tableSizeFor(1), 1);
81			assertEquals(tableSizeFor(2), 2);
82			assertEquals(tableSizeFor(3), 4);
83			assertEquals(tableSizeFor(15), 16);
84			assertEquals(tableSizeFor(16), 16);
85			assertEquals(tableSizeFor(17), 32);
86			int maxSize = 1 << 30;
87			assertEquals(tableSizeFor(maxSize - 1), maxSize);
88			assertEquals(tableSizeFor(maxSize), maxSize);
89			assertEquals(tableSizeFor(maxSize + 1), maxSize);
90			assertEquals(tableSizeFor(Integer.MAX_VALUE), maxSize);
91			}
92
93			@Test
94			public void capacityTest() {
95			HashMap<Integer, Integer> map = new HashMap<>();
96			assertNull(table(map));
97
98			map.put(1, 1);
99			assertEquals(capacity(map), 16);
100
101			map.putAll(IntStream.range(0, 64).boxed().collect(toMap(i -> i, i -> i)));
102			assertEquals(capacity(map), 128);
103			}
104			}