test/tck/ThreadLocalRandomTest.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;

import junit.framework.Test;
import junit.framework.TestSuite;

public class ThreadLocalRandomTest extends JSR166TestCase {

    public static void main(String[] args) {
        main(suite(), args);
    }
    public static Test suite() {
        return new TestSuite(ThreadLocalRandomTest.class);
    }

    /*
     * Testing coverage notes:
     *
     * We don't test randomness properties, but only that repeated
     * calls, up to NCALLS tries, produce at least one different
     * result.  For bounded versions, we sample various intervals
     * across multiples of primes.
     */

    // max numbers of calls to detect getting stuck on one value
    static final int NCALLS = 10000;

    // max sampled int bound
    static final int MAX_INT_BOUND = (1 << 28);

    // max sampled long bound
    static final long MAX_LONG_BOUND = (1L << 42);

    // Number of replications for other checks
    static final int REPS = 20;

    /**
     * setSeed throws UnsupportedOperationException
     */
    public void testSetSeed() {
        try {
            ThreadLocalRandom.current().setSeed(17);
            shouldThrow();
        } catch (UnsupportedOperationException success) {}
    }

    /**
     * Repeated calls to next (only accessible via reflection) produce
     * at least two distinct results, and repeated calls produce all
     * possible values.
     */
    public void testNext() throws ReflectiveOperationException {
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        try {
            java.lang.reflect.Method m
                = ThreadLocalRandom.class.getDeclaredMethod(
                    "next", new Class[] { int.class });
            m.setAccessible(true);

            int i;
            {
                int val = new java.util.Random().nextInt(4);
                for (i = 0; i < NCALLS; i++) {
                    int q = (int) m.invoke(rnd, new Object[] { 2 });
                    if (val == q) break;
                }
                assertTrue(i < NCALLS);
            }

            {
                int r = (int) m.invoke(rnd, new Object[] { 3 });
                for (i = 0; i < NCALLS; i++) {
                    int q = (int) m.invoke(rnd, new Object[] { 3 });
                    assertTrue(q < (1<<3));
                    if (r != q) break;
                }
                assertTrue(i < NCALLS);
            }
        } catch (SecurityException acceptable) {}
    }

    /**
     * Repeated calls to nextInt produce at least two distinct results
     */
    public void testNextInt() {
        int f = ThreadLocalRandom.current().nextInt();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextInt() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * Repeated calls to nextLong produce at least two distinct results
     */
    public void testNextLong() {
        long f = ThreadLocalRandom.current().nextLong();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextLong() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * Repeated calls to nextBoolean produce at least two distinct results
     */
    public void testNextBoolean() {
        boolean f = ThreadLocalRandom.current().nextBoolean();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextBoolean() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * Repeated calls to nextFloat produce at least two distinct results
     */
    public void testNextFloat() {
        float f = ThreadLocalRandom.current().nextFloat();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextFloat() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * Repeated calls to nextDouble produce at least two distinct results
     */
    public void testNextDouble() {
        double f = ThreadLocalRandom.current().nextDouble();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextDouble() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * Repeated calls to nextGaussian produce at least two distinct results
     */
    public void testNextGaussian() {
        double f = ThreadLocalRandom.current().nextGaussian();
        int i = 0;
        while (i < NCALLS && ThreadLocalRandom.current().nextGaussian() == f)
            ++i;
        assertTrue(i < NCALLS);
    }

    /**
     * nextInt(non-positive) throws IllegalArgumentException
     */
    public void testNextIntBoundNonPositive() {
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        for (int bound : new int[] { 0, -17, Integer.MIN_VALUE }) {
            try {
                rnd.nextInt(bound);
                shouldThrow();
            } catch (IllegalArgumentException success) {}
        }
    }

    /**
     * nextInt(least >= bound) throws IllegalArgumentException
     */
    public void testNextIntBadBounds() {
        int[][] badBoundss = {
            { 17, 2 },
            { -42, -42 },
            { Integer.MAX_VALUE, Integer.MIN_VALUE },
        };
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        for (int[] badBounds : badBoundss) {
            try {
                rnd.nextInt(badBounds[0], badBounds[1]);
                shouldThrow();
            } catch (IllegalArgumentException success) {}
        }
    }

    /**
     * nextInt(bound) returns 0 <= value < bound;
     * repeated calls produce at least two distinct results
     */
    public void testNextIntBounded() {
        // sample bound space across prime number increments
        for (int bound = 2; bound < MAX_INT_BOUND; bound += 524959) {
            int f = ThreadLocalRandom.current().nextInt(bound);
            assertTrue(0 <= f && f < bound);
            int i = 0;
            int j;
            while (i < NCALLS &&
                   (j = ThreadLocalRandom.current().nextInt(bound)) == f) {
                assertTrue(0 <= j && j < bound);
                ++i;
            }
            assertTrue(i < NCALLS);
        }
    }

    /**
     * nextInt(least, bound) returns least <= value < bound;
     * repeated calls produce at least two distinct results
     */
    public void testNextIntBounded2() {
        for (int least = -15485863; least < MAX_INT_BOUND; least += 524959) {
            for (int bound = least + 2; bound > least && bound < MAX_INT_BOUND; bound += 49979687) {
                int f = ThreadLocalRandom.current().nextInt(least, bound);
                assertTrue(least <= f && f < bound);
                int i = 0;
                int j;
                while (i < NCALLS &&
                       (j = ThreadLocalRandom.current().nextInt(least, bound)) == f) {
                    assertTrue(least <= j && j < bound);
                    ++i;
                }
                assertTrue(i < NCALLS);
            }
        }
    }

    /**
     * nextLong(non-positive) throws IllegalArgumentException
     */
    public void testNextLongBoundNonPositive() {
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        for (long bound : new long[] { 0L, -17L, Long.MIN_VALUE }) {
            try {
                rnd.nextLong(bound);
                shouldThrow();
            } catch (IllegalArgumentException success) {}
        }
    }

    /**
     * nextLong(least >= bound) throws IllegalArgumentException
     */
    public void testNextLongBadBounds() {
        long[][] badBoundss = {
            { 17L, 2L },
            { -42L, -42L },
            { Long.MAX_VALUE, Long.MIN_VALUE },
        };
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        for (long[] badBounds : badBoundss) {
            try {
                rnd.nextLong(badBounds[0], badBounds[1]);
                shouldThrow();
            } catch (IllegalArgumentException success) {}
        }
    }

    /**
     * nextLong(bound) returns 0 <= value < bound;
     * repeated calls produce at least two distinct results
     */
    public void testNextLongBounded() {
        for (long bound = 2; bound < MAX_LONG_BOUND; bound += 15485863) {
            long f = ThreadLocalRandom.current().nextLong(bound);
            assertTrue(0 <= f && f < bound);
            int i = 0;
            long j;
            while (i < NCALLS &&
                   (j = ThreadLocalRandom.current().nextLong(bound)) == f) {
                assertTrue(0 <= j && j < bound);
                ++i;
            }
            assertTrue(i < NCALLS);
        }
    }

    /**
     * nextLong(least, bound) returns least <= value < bound;
     * repeated calls produce at least two distinct results
     */
    public void testNextLongBounded2() {
        for (long least = -86028121; least < MAX_LONG_BOUND; least += 982451653L) {
            for (long bound = least + 2; bound > least && bound < MAX_LONG_BOUND; bound += Math.abs(bound * 7919)) {
                long f = ThreadLocalRandom.current().nextLong(least, bound);
                assertTrue(least <= f && f < bound);
                int i = 0;
                long j;
                while (i < NCALLS &&
                       (j = ThreadLocalRandom.current().nextLong(least, bound)) == f) {
                    assertTrue(least <= j && j < bound);
                    ++i;
                }
                assertTrue(i < NCALLS);
            }
        }
    }

    /**
     * nextDouble(non-positive) throws IllegalArgumentException
     */
    public void testNextDoubleBoundNonPositive() {
        ThreadLocalRandom rnd = ThreadLocalRandom.current();
        double[] badBounds = {
            0.0d,
            -17.0d,
            -Double.MIN_VALUE,
            Double.NEGATIVE_INFINITY,
            Double.NaN,
        };
        for (double bound : badBounds) {
            try {
                rnd.nextDouble(bound);
                shouldThrow();
            } catch (IllegalArgumentException success) {}
        }
    }

    /**
     * nextDouble(least, bound) returns least <= value < bound;
     * repeated calls produce at least two distinct results
     */
    public void testNextDoubleBounded2() {
        for (double least = 0.0001; least < 1.0e20; least *= 8) {
            for (double bound = least * 1.001; bound < 1.0e20; bound *= 16) {
                double f = ThreadLocalRandom.current().nextDouble(least, bound);
                assertTrue(least <= f && f < bound);
                int i = 0;
                double j;
                while (i < NCALLS &&
                       (j = ThreadLocalRandom.current().nextDouble(least, bound)) == f) {
                    assertTrue(least <= j && j < bound);
                    ++i;
                }
                assertTrue(i < NCALLS);
            }
        }
    }

    /**
     * Different threads produce different pseudo-random sequences
     */
    public void testDifferentSequences() {
        // Don't use main thread's ThreadLocalRandom - it is likely to
        // be polluted by previous tests.
        final AtomicReference<ThreadLocalRandom> threadLocalRandom =
            new AtomicReference<ThreadLocalRandom>();
        final AtomicLong rand = new AtomicLong();

        long firstRand = 0;
        ThreadLocalRandom firstThreadLocalRandom = null;

        Runnable getRandomState = new CheckedRunnable() {
            public void realRun() {
                ThreadLocalRandom current = ThreadLocalRandom.current();
                assertSame(current, ThreadLocalRandom.current());
                // test bug: the following is not guaranteed and not true in JDK8
                //                assertNotSame(current, threadLocalRandom.get());
                rand.set(current.nextLong());
                threadLocalRandom.set(current);
            }};

        Thread first = newStartedThread(getRandomState);
        awaitTermination(first);
        firstRand = rand.get();
        firstThreadLocalRandom = threadLocalRandom.get();

        for (int i = 0; i < NCALLS; i++) {
            Thread t = newStartedThread(getRandomState);
            awaitTermination(t);
            if (firstRand != rand.get())
                return;
        }
        fail("all threads generate the same pseudo-random sequence");
    }

}
Revision:	1.22
Committed:	Sun Nov 13 03:36:50 2016 UTC (7 years, 6 months ago) by jsr166
Branch:	MAIN
Changes since 1.21:	+35 -0 lines
Log Message:	revise (uselessly inaccessible) next(int) method javadoc, implementation and tests
#	Content
1	/*
2	* Written by Doug Lea with assistance from members of JCP JSR-166
3	* Expert Group and released to the public domain, as explained at
4	* http://creativecommons.org/publicdomain/zero/1.0/
5	*/
6
7	import java.util.concurrent.ThreadLocalRandom;
8	import java.util.concurrent.atomic.AtomicLong;
9	import java.util.concurrent.atomic.AtomicReference;
10
11	import junit.framework.Test;
12	import junit.framework.TestSuite;
13
14	public class ThreadLocalRandomTest extends JSR166TestCase {
15
16	public static void main(String[] args) {
17	main(suite(), args);
18	}
19	public static Test suite() {
20	return new TestSuite(ThreadLocalRandomTest.class);
21	}
22
23	/*
24	* Testing coverage notes:
25	*
26	* We don't test randomness properties, but only that repeated
27	* calls, up to NCALLS tries, produce at least one different
28	* result. For bounded versions, we sample various intervals
29	* across multiples of primes.
30	*/
31
32	// max numbers of calls to detect getting stuck on one value
33	static final int NCALLS = 10000;
34
35	// max sampled int bound
36	static final int MAX_INT_BOUND = (1 << 28);
37
38	// max sampled long bound
39	static final long MAX_LONG_BOUND = (1L << 42);
40
41	// Number of replications for other checks
42	static final int REPS = 20;
43
44	/**
45	* setSeed throws UnsupportedOperationException
46	*/
47	public void testSetSeed() {
48	try {
49	ThreadLocalRandom.current().setSeed(17);
50	shouldThrow();
51	} catch (UnsupportedOperationException success) {}
52	}
53
54	/**
55	* Repeated calls to next (only accessible via reflection) produce
56	* at least two distinct results, and repeated calls produce all
57	* possible values.
58	*/
59	public void testNext() throws ReflectiveOperationException {
60	ThreadLocalRandom rnd = ThreadLocalRandom.current();
61	try {
62	java.lang.reflect.Method m
63	= ThreadLocalRandom.class.getDeclaredMethod(
64	"next", new Class[] { int.class });
65	m.setAccessible(true);
66
67	int i;
68	{
69	int val = new java.util.Random().nextInt(4);
70	for (i = 0; i < NCALLS; i++) {
71	int q = (int) m.invoke(rnd, new Object[] { 2 });
72	if (val == q) break;
73	}
74	assertTrue(i < NCALLS);
75	}
76
77	{
78	int r = (int) m.invoke(rnd, new Object[] { 3 });
79	for (i = 0; i < NCALLS; i++) {
80	int q = (int) m.invoke(rnd, new Object[] { 3 });
81	assertTrue(q < (1<<3));
82	if (r != q) break;
83	}
84	assertTrue(i < NCALLS);
85	}
86	} catch (SecurityException acceptable) {}
87	}
88
89	/**
90	* Repeated calls to nextInt produce at least two distinct results
91	*/
92	public void testNextInt() {
93	int f = ThreadLocalRandom.current().nextInt();
94	int i = 0;
95	while (i < NCALLS && ThreadLocalRandom.current().nextInt() == f)
96	++i;
97	assertTrue(i < NCALLS);
98	}
99
100	/**
101	* Repeated calls to nextLong produce at least two distinct results
102	*/
103	public void testNextLong() {
104	long f = ThreadLocalRandom.current().nextLong();
105	int i = 0;
106	while (i < NCALLS && ThreadLocalRandom.current().nextLong() == f)
107	++i;
108	assertTrue(i < NCALLS);
109	}
110
111	/**
112	* Repeated calls to nextBoolean produce at least two distinct results
113	*/
114	public void testNextBoolean() {
115	boolean f = ThreadLocalRandom.current().nextBoolean();
116	int i = 0;
117	while (i < NCALLS && ThreadLocalRandom.current().nextBoolean() == f)
118	++i;
119	assertTrue(i < NCALLS);
120	}
121
122	/**
123	* Repeated calls to nextFloat produce at least two distinct results
124	*/
125	public void testNextFloat() {
126	float f = ThreadLocalRandom.current().nextFloat();
127	int i = 0;
128	while (i < NCALLS && ThreadLocalRandom.current().nextFloat() == f)
129	++i;
130	assertTrue(i < NCALLS);
131	}
132
133	/**
134	* Repeated calls to nextDouble produce at least two distinct results
135	*/
136	public void testNextDouble() {
137	double f = ThreadLocalRandom.current().nextDouble();
138	int i = 0;
139	while (i < NCALLS && ThreadLocalRandom.current().nextDouble() == f)
140	++i;
141	assertTrue(i < NCALLS);
142	}
143
144	/**
145	* Repeated calls to nextGaussian produce at least two distinct results
146	*/
147	public void testNextGaussian() {
148	double f = ThreadLocalRandom.current().nextGaussian();
149	int i = 0;
150	while (i < NCALLS && ThreadLocalRandom.current().nextGaussian() == f)
151	++i;
152	assertTrue(i < NCALLS);
153	}
154
155	/**
156	* nextInt(non-positive) throws IllegalArgumentException
157	*/
158	public void testNextIntBoundNonPositive() {
159	ThreadLocalRandom rnd = ThreadLocalRandom.current();
160	for (int bound : new int[] { 0, -17, Integer.MIN_VALUE }) {
161	try {
162	rnd.nextInt(bound);
163	shouldThrow();
164	} catch (IllegalArgumentException success) {}
165	}
166	}
167
168	/**
169	* nextInt(least >= bound) throws IllegalArgumentException
170	*/
171	public void testNextIntBadBounds() {
172	int[][] badBoundss = {
173	{ 17, 2 },
174	{ -42, -42 },
175	{ Integer.MAX_VALUE, Integer.MIN_VALUE },
176	};
177	ThreadLocalRandom rnd = ThreadLocalRandom.current();
178	for (int[] badBounds : badBoundss) {
179	try {
180	rnd.nextInt(badBounds[0], badBounds[1]);
181	shouldThrow();
182	} catch (IllegalArgumentException success) {}
183	}
184	}
185
186	/**
187	* nextInt(bound) returns 0 <= value < bound;
188	* repeated calls produce at least two distinct results
189	*/
190	public void testNextIntBounded() {
191	// sample bound space across prime number increments
192	for (int bound = 2; bound < MAX_INT_BOUND; bound += 524959) {
193	int f = ThreadLocalRandom.current().nextInt(bound);
194	assertTrue(0 <= f && f < bound);
195	int i = 0;
196	int j;
197	while (i < NCALLS &&
198	(j = ThreadLocalRandom.current().nextInt(bound)) == f) {
199	assertTrue(0 <= j && j < bound);
200	++i;
201	}
202	assertTrue(i < NCALLS);
203	}
204	}
205
206	/**
207	* nextInt(least, bound) returns least <= value < bound;
208	* repeated calls produce at least two distinct results
209	*/
210	public void testNextIntBounded2() {
211	for (int least = -15485863; least < MAX_INT_BOUND; least += 524959) {
212	for (int bound = least + 2; bound > least && bound < MAX_INT_BOUND; bound += 49979687) {
213	int f = ThreadLocalRandom.current().nextInt(least, bound);
214	assertTrue(least <= f && f < bound);
215	int i = 0;
216	int j;
217	while (i < NCALLS &&
218	(j = ThreadLocalRandom.current().nextInt(least, bound)) == f) {
219	assertTrue(least <= j && j < bound);
220	++i;
221	}
222	assertTrue(i < NCALLS);
223	}
224	}
225	}
226
227	/**
228	* nextLong(non-positive) throws IllegalArgumentException
229	*/
230	public void testNextLongBoundNonPositive() {
231	ThreadLocalRandom rnd = ThreadLocalRandom.current();
232	for (long bound : new long[] { 0L, -17L, Long.MIN_VALUE }) {
233	try {
234	rnd.nextLong(bound);
235	shouldThrow();
236	} catch (IllegalArgumentException success) {}
237	}
238	}
239
240	/**
241	* nextLong(least >= bound) throws IllegalArgumentException
242	*/
243	public void testNextLongBadBounds() {
244	long[][] badBoundss = {
245	{ 17L, 2L },
246	{ -42L, -42L },
247	{ Long.MAX_VALUE, Long.MIN_VALUE },
248	};
249	ThreadLocalRandom rnd = ThreadLocalRandom.current();
250	for (long[] badBounds : badBoundss) {
251	try {
252	rnd.nextLong(badBounds[0], badBounds[1]);
253	shouldThrow();
254	} catch (IllegalArgumentException success) {}
255	}
256	}
257
258	/**
259	* nextLong(bound) returns 0 <= value < bound;
260	* repeated calls produce at least two distinct results
261	*/
262	public void testNextLongBounded() {
263	for (long bound = 2; bound < MAX_LONG_BOUND; bound += 15485863) {
264	long f = ThreadLocalRandom.current().nextLong(bound);
265	assertTrue(0 <= f && f < bound);
266	int i = 0;
267	long j;
268	while (i < NCALLS &&
269	(j = ThreadLocalRandom.current().nextLong(bound)) == f) {
270	assertTrue(0 <= j && j < bound);
271	++i;
272	}
273	assertTrue(i < NCALLS);
274	}
275	}
276
277	/**
278	* nextLong(least, bound) returns least <= value < bound;
279	* repeated calls produce at least two distinct results
280	*/
281	public void testNextLongBounded2() {
282	for (long least = -86028121; least < MAX_LONG_BOUND; least += 982451653L) {
283	for (long bound = least + 2; bound > least && bound < MAX_LONG_BOUND; bound += Math.abs(bound * 7919)) {
284	long f = ThreadLocalRandom.current().nextLong(least, bound);
285	assertTrue(least <= f && f < bound);
286	int i = 0;
287	long j;
288	while (i < NCALLS &&
289	(j = ThreadLocalRandom.current().nextLong(least, bound)) == f) {
290	assertTrue(least <= j && j < bound);
291	++i;
292	}
293	assertTrue(i < NCALLS);
294	}
295	}
296	}
297
298	/**
299	* nextDouble(non-positive) throws IllegalArgumentException
300	*/
301	public void testNextDoubleBoundNonPositive() {
302	ThreadLocalRandom rnd = ThreadLocalRandom.current();
303	double[] badBounds = {
304	0.0d,
305	-17.0d,
306	-Double.MIN_VALUE,
307	Double.NEGATIVE_INFINITY,
308	Double.NaN,
309	};
310	for (double bound : badBounds) {
311	try {
312	rnd.nextDouble(bound);
313	shouldThrow();
314	} catch (IllegalArgumentException success) {}
315	}
316	}
317
318	/**
319	* nextDouble(least, bound) returns least <= value < bound;
320	* repeated calls produce at least two distinct results
321	*/
322	public void testNextDoubleBounded2() {
323	for (double least = 0.0001; least < 1.0e20; least *= 8) {
324	for (double bound = least * 1.001; bound < 1.0e20; bound *= 16) {
325	double f = ThreadLocalRandom.current().nextDouble(least, bound);
326	assertTrue(least <= f && f < bound);
327	int i = 0;
328	double j;
329	while (i < NCALLS &&
330	(j = ThreadLocalRandom.current().nextDouble(least, bound)) == f) {
331	assertTrue(least <= j && j < bound);
332	++i;
333	}
334	assertTrue(i < NCALLS);
335	}
336	}
337	}
338
339	/**
340	* Different threads produce different pseudo-random sequences
341	*/
342	public void testDifferentSequences() {
343	// Don't use main thread's ThreadLocalRandom - it is likely to
344	// be polluted by previous tests.
345	final AtomicReference<ThreadLocalRandom> threadLocalRandom =
346	new AtomicReference<ThreadLocalRandom>();
347	final AtomicLong rand = new AtomicLong();
348
349	long firstRand = 0;
350	ThreadLocalRandom firstThreadLocalRandom = null;
351
352	Runnable getRandomState = new CheckedRunnable() {
353	public void realRun() {
354	ThreadLocalRandom current = ThreadLocalRandom.current();
355	assertSame(current, ThreadLocalRandom.current());
356	// test bug: the following is not guaranteed and not true in JDK8
357	// assertNotSame(current, threadLocalRandom.get());
358	rand.set(current.nextLong());
359	threadLocalRandom.set(current);
360	}};
361
362	Thread first = newStartedThread(getRandomState);
363	awaitTermination(first);
364	firstRand = rand.get();
365	firstThreadLocalRandom = threadLocalRandom.get();
366
367	for (int i = 0; i < NCALLS; i++) {
368	Thread t = newStartedThread(getRandomState);
369	awaitTermination(t);
370	if (firstRand != rand.get())
371	return;
372	}
373	fail("all threads generate the same pseudo-random sequence");
374	}
375
376	}