test/loops/NavigableSetCheck.java

/**
 * @test
 * @synopsis Times and checks basic set operations
 */
import java.util.*;
import java.io.*;

public class NavigableSetCheck {

    static int absentSize;
    static int absentMask;
    static Integer[] absent;

    static final Integer MISSING = new Integer(Integer.MIN_VALUE);

    static TestTimer timer = new TestTimer();

    static void reallyAssert(boolean b) {
        if (!b) throw new Error("Failed Assertion");
    }

    public static void main(String[] args) throws Exception {
        Class setClass = null;
        int numTests = 50;
        int size = 50000;

        if (args.length > 0) {
            try {
                setClass = Class.forName(args[0]);
            } catch(ClassNotFoundException e) {
                throw new RuntimeException("Class " + args[0] + " not found.");
            }
        }


        if (args.length > 1) 
            numTests = Integer.parseInt(args[1]);

        if (args.length > 2) 
            size = Integer.parseInt(args[2]);

        System.out.println("Testing " + setClass.getName() + " trials: " + numTests + " size: " + size);


        absentSize = 8;
        while (absentSize < size) absentSize <<= 1;
        absentMask = absentSize - 1;
        absent = new Integer[absentSize];

        for (int i = 0; i < absentSize; ++i) 
            absent[i] = new Integer(i * 2);

        Integer[] key = new Integer[size];
        for (int i = 0; i < size; ++i) 
            key[i] = new Integer(i * 2 + 1);


        for (int rep = 0; rep < numTests; ++rep) {
            runTest(newSet(setClass), key);
        }

        TestTimer.printStats();

    }

    static NavigableSet newSet(Class cl) {
        try {
            NavigableSet m = (NavigableSet)cl.newInstance();
            return m;
        } catch(Exception e) {
            throw new RuntimeException("Can't instantiate " + cl + ": " + e);
        }
    }


    static void runTest(NavigableSet s, Integer[] key) {
        shuffle(key);
        int size = key.length;
        long startTime = System.currentTimeMillis();
        test(s, key);
        long time = System.currentTimeMillis() - startTime;
    }

    static void t1(String nm, int n, NavigableSet s, Integer[] key, int expect) {
        int sum = 0;
        int iters = 4;
        timer.start(nm, n * iters);
        for (int j = 0; j < iters; ++j) {
            for (int i = 0; i < n; i++) {
                if (s.contains(key[i])) ++sum;
            }
        }
        timer.finish(); 
        reallyAssert (sum == expect * iters);
    }

    static void t2(String nm, int n, NavigableSet s, Integer[] key, int expect) {
        int sum = 0;
        timer.start(nm, n);
        for (int i = 0; i < n; i++) {
            if (s.remove(key[i])) ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == expect);
    }

    static void t3(String nm, int n, NavigableSet s, Integer[] key, int expect) {
        int sum = 0;
        timer.start(nm, n);
        for (int i = 0; i < n; i++) {
            if (s.add(key[i])) ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == expect);
    }

    static void t4(String nm, int n, NavigableSet s, Integer[] key, int expect) {
        int sum = 0;
        timer.start(nm, n);
        for (int i = 0; i < n; i++) {
            if (s.contains(key[i])) ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == expect);
    }

    static void t5(String nm, int n, NavigableSet s, Integer[] key, int expect) {
        int sum = 0;
        timer.start(nm, n/2);
        for (int i = n-2; i >= 0; i-=2) {
            if (s.remove(key[i])) ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == expect);
    }

    static void t6(String nm, int n, NavigableSet s, Integer[] k1, Integer[] k2) {
        int sum = 0;
        timer.start(nm, n * 2);
        for (int i = 0; i < n; i++) {
            if (s.contains(k1[i])) ++sum;
            if (s.contains(k2[i & absentMask])) ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == n);
    }

    static void t7(String nm, int n, NavigableSet s, Integer[] k1, Integer[] k2) {
        int sum = 0;
        timer.start(nm, n * 2);
        for (int i = 0; i < n; i++) {
            if (s.contains(k1[i])) ++sum;
            if (s.contains(k2[i & absentMask])) ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == n);
    }

    static void t8(String nm, int n, NavigableSet s, Integer[] key, int expect) {
        int sum = 0;
        timer.start(nm, n);
        for (int i = 0; i < n; i++) {
            if (s.contains(key[i])) ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == expect);
    }


    static void higherTest(NavigableSet s) {
        int sum = 0;
        int iters = s.size();
        timer.start("Higher                 ", iters);
        Object e = s.first();
        while (e != null) {
            ++sum;
            e = s.higher(e);
        }
        timer.finish(); 
        reallyAssert (sum == iters);
    }

    static void lowerTest(NavigableSet s) {
        int sum = 0;
        int iters = s.size();
        timer.start("Lower                  ", iters);
        Object e = s.first();
        while (e != null) {
            ++sum;
            e = s.higher(e);
        }
        timer.finish(); 
        reallyAssert (sum == iters);
    }

    static void ceilingTest(NavigableSet s) {
        int sum = 0;
        int iters = s.size();
        if (iters > absentSize) iters = absentSize;
        timer.start("Ceiling                ", iters);
        for (int i = 0; i < iters; ++i) {
            Object e = s.ceiling(absent[i]);
            if (e != null)
                ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == iters);
    }

    static void floorTest(NavigableSet s) {
        int sum = 0;
        int iters = s.size();
        if (iters > absentSize) iters = absentSize;
        timer.start("Floor                  ", iters);
        for (int i = 1; i < iters; ++i) {
            Object e = s.floor(absent[i]);
            if (e != null)
                ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == iters-1);
    }


    static void ktest(NavigableSet s, int size, Integer[] key) {
        timer.start("Contains               ", size);
        int sum = 0;
        for (int i = 0; i < size; i++) {
            if (s.contains(key[i])) ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == size);
    }


    static void ittest1(NavigableSet s, int size) {
        int sum = 0;
        timer.start("Iter Key               ", size);
        for (Iterator it = s.iterator(); it.hasNext(); ) {
            if(it.next() != MISSING)
                ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == size);
    }

    static void ittest(NavigableSet s, int size) {
        ittest1(s, size);
    }

    static void rittest1(NavigableSet s, int size) {
        int sum = 0;
        timer.start("Desc Iter Key          ", size);
        for (Iterator it = s.descendingIterator(); it.hasNext(); ) {
            if(it.next() != MISSING)
                ++sum;
        }
        timer.finish(); 
        reallyAssert (sum == size);
    }

    static void rittest(NavigableSet s, int size) {
        rittest1(s, size);
    }


    static void rtest(NavigableSet s, int size) {
        timer.start("Remove (iterator)      ", size);
        for (Iterator it = s.iterator(); it.hasNext(); ) {
            it.next();
            it.remove();
        }
        timer.finish(); 
    }


    static void dtest(NavigableSet s, int size, Integer[] key) {
        timer.start("Add (addAll)           ", size * 2);
        NavigableSet s2 = null;
        try {
            s2 = (NavigableSet) (s.getClass().newInstance());
            s2.addAll(s);
        }
        catch (Exception e) { e.printStackTrace(); return; }
        timer.finish(); 
    
        timer.start("Iter Equals            ", size * 2);
        boolean eqt = s2.equals(s) && s.equals(s2);
        reallyAssert (eqt);
        timer.finish(); 

        timer.start("Iter HashCode          ", size * 2);
        int shc = s.hashCode();
        int s2hc = s2.hashCode();
        reallyAssert (shc == s2hc);
        timer.finish(); 

        timer.start("Add (present)          ", size);
        s2.addAll(s);
        timer.finish(); 

        t6("Contains               ", size, s2, key, absent);

        boolean as2 = s2.add(absent[absentSize-1]);
        reallyAssert(as2);
        timer.start("Iter Equals            ", size * 2);
        eqt = s2.equals(s) && s.equals(s2);
        if (as2)
            reallyAssert (!eqt);
        timer.finish(); 

        timer.start("Iter HashCode          ", size * 2);
        int s1h = s.hashCode();
        int s2h = s2.hashCode();
        if (as2)
            reallyAssert (s1h != s2h);
        timer.finish(); 

        timer.start("Clear                  ", size);
        s.clear();
        s2.clear();
        timer.finish(); 
        reallyAssert (s2.isEmpty() && s.isEmpty());
    }


    static void test(NavigableSet s, Integer[] key) {
        int size = key.length;

        t3("Add (absent)           ", size, s, key, size);
        t3("Add (present)          ", size, s, key, 0);
        t7("ContainsKey            ", size, s, key, absent);
        t4("ContainsKey            ", size, s, key, size);
        ktest(s, size, key);
        t4("Contains               ", absentSize, s, absent, 0);
        t6("Contains               ", size, s, key, absent);
        t1("Contains (present)     ", size, s, key, size);
        t1("Contains (absent)      ", absentSize, s, absent, 0);
        t2("Remove (absent)        ", absentSize, s, absent, 0);
        t5("Remove (present)       ", size, s, key, size / 2);
        t3("Add (half present)     ", size, s, key, size / 2);

        ittest(s, size);
        rittest(s, size);
        higherTest(s);
        ceilingTest(s);
        floorTest(s);
        lowerTest(s);
        rtest(s, size);

        t4("Contains               ", size, s, key, 0);
        t2("Remove (absent)        ", size, s, key, 0);
        t3("Add (presized)         ", size, s, key, size);
        dtest(s, size, key);
    }

    static class TestTimer {
        private String name;
        private long numOps;
        private long startTime;
        private String cname;

        static final java.util.TreeMap accum = new java.util.TreeMap();
    
        static void printStats() {
            for (Iterator it = accum.entrySet().iterator(); it.hasNext(); ) {
                Map.Entry e = (Map.Entry)(it.next());
                Stats stats = ((Stats)(e.getValue()));
                int n = stats.number;
                double t;
                if (n > 0) 
                    t = stats.sum / n;
                else
                    t = stats.least;
                long nano = Math.round(1000000.0 * t);
                System.out.println(e.getKey() + ": " + nano);
            }
        }
    
        void start(String name, long numOps) {
            this.name = name;
            this.cname = classify();
            this.numOps = numOps;
            startTime = System.currentTimeMillis();
        }
    

        String classify() {
            if (name.startsWith("Contains"))
                return "Contains               ";
            else if (name.startsWith("Add"))
                return "Add                    ";
            else if (name.startsWith("Remove"))
                return "Remove                 ";
            else if (name.startsWith("Iter"))
                return "Iter                   ";
            else 
                return null;
        }

        void finish() {
            long endTime = System.currentTimeMillis();
            long time = endTime - startTime;
            double timePerOp = ((double)time)/numOps;

            Object st = accum.get(name);
            if (st == null)
                accum.put(name, new Stats(timePerOp));
            else {
                Stats stats = (Stats) st;
                stats.sum += timePerOp;
                stats.number++;
                if (timePerOp < stats.least) stats.least = timePerOp;
            }

            if (cname != null) {
                st = accum.get(cname);
                if (st == null)
                    accum.put(cname, new Stats(timePerOp));
                else {
                    Stats stats = (Stats) st;
                    stats.sum += timePerOp;
                    stats.number++;
                    if (timePerOp < stats.least) stats.least = timePerOp;
                }
            }

        }

    }

    static class Stats {
        double sum = 0;
        double least;
        int number = 0;
        Stats(double t) { least = t; }
    }

    static Random rng = new Random();

    static void shuffle(Integer[] keys) {
        int size = keys.length;
        for (int i=size; i>1; i--) {
            int r = rng.nextInt(i);
            Integer t = keys[i-1];
            keys[i-1] = keys[r];
            keys[r] = t;
        }
    }

}

Revision:	1.1
Committed:	Mon May 2 19:19:38 2005 UTC (19 years ago) by dl
Branch:	MAIN
Log Message:	Put misc performance tests into CVS
#	Content
1	/**
2	* @test
3	* @synopsis Times and checks basic set operations
4	*/
5	import java.util.*;
6	import java.io.*;
7
8	public class NavigableSetCheck {
9
10	static int absentSize;
11	static int absentMask;
12	static Integer[] absent;
13
14	static final Integer MISSING = new Integer(Integer.MIN_VALUE);
15
16	static TestTimer timer = new TestTimer();
17
18	static void reallyAssert(boolean b) {
19	if (!b) throw new Error("Failed Assertion");
20	}
21
22	public static void main(String[] args) throws Exception {
23	Class setClass = null;
24	int numTests = 50;
25	int size = 50000;
26
27	if (args.length > 0) {
28	try {
29	setClass = Class.forName(args[0]);
30	} catch(ClassNotFoundException e) {
31	throw new RuntimeException("Class " + args[0] + " not found.");
32	}
33	}
34
35
36	if (args.length > 1)
37	numTests = Integer.parseInt(args[1]);
38
39	if (args.length > 2)
40	size = Integer.parseInt(args[2]);
41
42	System.out.println("Testing " + setClass.getName() + " trials: " + numTests + " size: " + size);
43
44
45	absentSize = 8;
46	while (absentSize < size) absentSize <<= 1;
47	absentMask = absentSize - 1;
48	absent = new Integer[absentSize];
49
50	for (int i = 0; i < absentSize; ++i)
51	absent[i] = new Integer(i * 2);
52
53	Integer[] key = new Integer[size];
54	for (int i = 0; i < size; ++i)
55	key[i] = new Integer(i * 2 + 1);
56
57
58	for (int rep = 0; rep < numTests; ++rep) {
59	runTest(newSet(setClass), key);
60	}
61
62	TestTimer.printStats();
63
64	}
65
66	static NavigableSet newSet(Class cl) {
67	try {
68	NavigableSet m = (NavigableSet)cl.newInstance();
69	return m;
70	} catch(Exception e) {
71	throw new RuntimeException("Can't instantiate " + cl + ": " + e);
72	}
73	}
74
75
76	static void runTest(NavigableSet s, Integer[] key) {
77	shuffle(key);
78	int size = key.length;
79	long startTime = System.currentTimeMillis();
80	test(s, key);
81	long time = System.currentTimeMillis() - startTime;
82	}
83
84	static void t1(String nm, int n, NavigableSet s, Integer[] key, int expect) {
85	int sum = 0;
86	int iters = 4;
87	timer.start(nm, n * iters);
88	for (int j = 0; j < iters; ++j) {
89	for (int i = 0; i < n; i++) {
90	if (s.contains(key[i])) ++sum;
91	}
92	}
93	timer.finish();
94	reallyAssert (sum == expect * iters);
95	}
96
97	static void t2(String nm, int n, NavigableSet s, Integer[] key, int expect) {
98	int sum = 0;
99	timer.start(nm, n);
100	for (int i = 0; i < n; i++) {
101	if (s.remove(key[i])) ++sum;
102	}
103	timer.finish();
104	reallyAssert (sum == expect);
105	}
106
107	static void t3(String nm, int n, NavigableSet s, Integer[] key, int expect) {
108	int sum = 0;
109	timer.start(nm, n);
110	for (int i = 0; i < n; i++) {
111	if (s.add(key[i])) ++sum;
112	}
113	timer.finish();
114	reallyAssert (sum == expect);
115	}
116
117	static void t4(String nm, int n, NavigableSet s, Integer[] key, int expect) {
118	int sum = 0;
119	timer.start(nm, n);
120	for (int i = 0; i < n; i++) {
121	if (s.contains(key[i])) ++sum;
122	}
123	timer.finish();
124	reallyAssert (sum == expect);
125	}
126
127	static void t5(String nm, int n, NavigableSet s, Integer[] key, int expect) {
128	int sum = 0;
129	timer.start(nm, n/2);
130	for (int i = n-2; i >= 0; i-=2) {
131	if (s.remove(key[i])) ++sum;
132	}
133	timer.finish();
134	reallyAssert (sum == expect);
135	}
136
137	static void t6(String nm, int n, NavigableSet s, Integer[] k1, Integer[] k2) {
138	int sum = 0;
139	timer.start(nm, n * 2);
140	for (int i = 0; i < n; i++) {
141	if (s.contains(k1[i])) ++sum;
142	if (s.contains(k2[i & absentMask])) ++sum;
143	}
144	timer.finish();
145	reallyAssert (sum == n);
146	}
147
148	static void t7(String nm, int n, NavigableSet s, Integer[] k1, Integer[] k2) {
149	int sum = 0;
150	timer.start(nm, n * 2);
151	for (int i = 0; i < n; i++) {
152	if (s.contains(k1[i])) ++sum;
153	if (s.contains(k2[i & absentMask])) ++sum;
154	}
155	timer.finish();
156	reallyAssert (sum == n);
157	}
158
159	static void t8(String nm, int n, NavigableSet s, Integer[] key, int expect) {
160	int sum = 0;
161	timer.start(nm, n);
162	for (int i = 0; i < n; i++) {
163	if (s.contains(key[i])) ++sum;
164	}
165	timer.finish();
166	reallyAssert (sum == expect);
167	}
168
169
170	static void higherTest(NavigableSet s) {
171	int sum = 0;
172	int iters = s.size();
173	timer.start("Higher ", iters);
174	Object e = s.first();
175	while (e != null) {
176	++sum;
177	e = s.higher(e);
178	}
179	timer.finish();
180	reallyAssert (sum == iters);
181	}
182
183	static void lowerTest(NavigableSet s) {
184	int sum = 0;
185	int iters = s.size();
186	timer.start("Lower ", iters);
187	Object e = s.first();
188	while (e != null) {
189	++sum;
190	e = s.higher(e);
191	}
192	timer.finish();
193	reallyAssert (sum == iters);
194	}
195
196	static void ceilingTest(NavigableSet s) {
197	int sum = 0;
198	int iters = s.size();
199	if (iters > absentSize) iters = absentSize;
200	timer.start("Ceiling ", iters);
201	for (int i = 0; i < iters; ++i) {
202	Object e = s.ceiling(absent[i]);
203	if (e != null)
204	++sum;
205	}
206	timer.finish();
207	reallyAssert (sum == iters);
208	}
209
210	static void floorTest(NavigableSet s) {
211	int sum = 0;
212	int iters = s.size();
213	if (iters > absentSize) iters = absentSize;
214	timer.start("Floor ", iters);
215	for (int i = 1; i < iters; ++i) {
216	Object e = s.floor(absent[i]);
217	if (e != null)
218	++sum;
219	}
220	timer.finish();
221	reallyAssert (sum == iters-1);
222	}
223
224
225	static void ktest(NavigableSet s, int size, Integer[] key) {
226	timer.start("Contains ", size);
227	int sum = 0;
228	for (int i = 0; i < size; i++) {
229	if (s.contains(key[i])) ++sum;
230	}
231	timer.finish();
232	reallyAssert (sum == size);
233	}
234
235
236	static void ittest1(NavigableSet s, int size) {
237	int sum = 0;
238	timer.start("Iter Key ", size);
239	for (Iterator it = s.iterator(); it.hasNext(); ) {
240	if(it.next() != MISSING)
241	++sum;
242	}
243	timer.finish();
244	reallyAssert (sum == size);
245	}
246
247	static void ittest(NavigableSet s, int size) {
248	ittest1(s, size);
249	}
250
251	static void rittest1(NavigableSet s, int size) {
252	int sum = 0;
253	timer.start("Desc Iter Key ", size);
254	for (Iterator it = s.descendingIterator(); it.hasNext(); ) {
255	if(it.next() != MISSING)
256	++sum;
257	}
258	timer.finish();
259	reallyAssert (sum == size);
260	}
261
262	static void rittest(NavigableSet s, int size) {
263	rittest1(s, size);
264	}
265
266
267	static void rtest(NavigableSet s, int size) {
268	timer.start("Remove (iterator) ", size);
269	for (Iterator it = s.iterator(); it.hasNext(); ) {
270	it.next();
271	it.remove();
272	}
273	timer.finish();
274	}
275
276
277
278	static void dtest(NavigableSet s, int size, Integer[] key) {
279	timer.start("Add (addAll) ", size * 2);
280	NavigableSet s2 = null;
281	try {
282	s2 = (NavigableSet) (s.getClass().newInstance());
283	s2.addAll(s);
284	}
285	catch (Exception e) { e.printStackTrace(); return; }
286	timer.finish();
287
288	timer.start("Iter Equals ", size * 2);
289	boolean eqt = s2.equals(s) && s.equals(s2);
290	reallyAssert (eqt);
291	timer.finish();
292
293	timer.start("Iter HashCode ", size * 2);
294	int shc = s.hashCode();
295	int s2hc = s2.hashCode();
296	reallyAssert (shc == s2hc);
297	timer.finish();
298
299	timer.start("Add (present) ", size);
300	s2.addAll(s);
301	timer.finish();
302
303	t6("Contains ", size, s2, key, absent);
304
305	boolean as2 = s2.add(absent[absentSize-1]);
306	reallyAssert(as2);
307	timer.start("Iter Equals ", size * 2);
308	eqt = s2.equals(s) && s.equals(s2);
309	if (as2)
310	reallyAssert (!eqt);
311	timer.finish();
312
313	timer.start("Iter HashCode ", size * 2);
314	int s1h = s.hashCode();
315	int s2h = s2.hashCode();
316	if (as2)
317	reallyAssert (s1h != s2h);
318	timer.finish();
319
320	timer.start("Clear ", size);
321	s.clear();
322	s2.clear();
323	timer.finish();
324	reallyAssert (s2.isEmpty() && s.isEmpty());
325	}
326
327
328
329	static void test(NavigableSet s, Integer[] key) {
330	int size = key.length;
331
332	t3("Add (absent) ", size, s, key, size);
333	t3("Add (present) ", size, s, key, 0);
334	t7("ContainsKey ", size, s, key, absent);
335	t4("ContainsKey ", size, s, key, size);
336	ktest(s, size, key);
337	t4("Contains ", absentSize, s, absent, 0);
338	t6("Contains ", size, s, key, absent);
339	t1("Contains (present) ", size, s, key, size);
340	t1("Contains (absent) ", absentSize, s, absent, 0);
341	t2("Remove (absent) ", absentSize, s, absent, 0);
342	t5("Remove (present) ", size, s, key, size / 2);
343	t3("Add (half present) ", size, s, key, size / 2);
344
345	ittest(s, size);
346	rittest(s, size);
347	higherTest(s);
348	ceilingTest(s);
349	floorTest(s);
350	lowerTest(s);
351	rtest(s, size);
352
353	t4("Contains ", size, s, key, 0);
354	t2("Remove (absent) ", size, s, key, 0);
355	t3("Add (presized) ", size, s, key, size);
356	dtest(s, size, key);
357	}
358
359	static class TestTimer {
360	private String name;
361	private long numOps;
362	private long startTime;
363	private String cname;
364
365	static final java.util.TreeMap accum = new java.util.TreeMap();
366
367	static void printStats() {
368	for (Iterator it = accum.entrySet().iterator(); it.hasNext(); ) {
369	Map.Entry e = (Map.Entry)(it.next());
370	Stats stats = ((Stats)(e.getValue()));
371	int n = stats.number;
372	double t;
373	if (n > 0)
374	t = stats.sum / n;
375	else
376	t = stats.least;
377	long nano = Math.round(1000000.0 * t);
378	System.out.println(e.getKey() + ": " + nano);
379	}
380	}
381
382	void start(String name, long numOps) {
383	this.name = name;
384	this.cname = classify();
385	this.numOps = numOps;
386	startTime = System.currentTimeMillis();
387	}
388
389
390	String classify() {
391	if (name.startsWith("Contains"))
392	return "Contains ";
393	else if (name.startsWith("Add"))
394	return "Add ";
395	else if (name.startsWith("Remove"))
396	return "Remove ";
397	else if (name.startsWith("Iter"))
398	return "Iter ";
399	else
400	return null;
401	}
402
403	void finish() {
404	long endTime = System.currentTimeMillis();
405	long time = endTime - startTime;
406	double timePerOp = ((double)time)/numOps;
407
408	Object st = accum.get(name);
409	if (st == null)
410	accum.put(name, new Stats(timePerOp));
411	else {
412	Stats stats = (Stats) st;
413	stats.sum += timePerOp;
414	stats.number++;
415	if (timePerOp < stats.least) stats.least = timePerOp;
416	}
417
418	if (cname != null) {
419	st = accum.get(cname);
420	if (st == null)
421	accum.put(cname, new Stats(timePerOp));
422	else {
423	Stats stats = (Stats) st;
424	stats.sum += timePerOp;
425	stats.number++;
426	if (timePerOp < stats.least) stats.least = timePerOp;
427	}
428	}
429
430	}
431
432	}
433
434	static class Stats {
435	double sum = 0;
436	double least;
437	int number = 0;
438	Stats(double t) { least = t; }
439	}
440
441	static Random rng = new Random();
442
443	static void shuffle(Integer[] keys) {
444	int size = keys.length;
445	for (int i=size; i>1; i--) {
446	int r = rng.nextInt(i);
447	Integer t = keys[i-1];
448	keys[i-1] = keys[r];
449	keys[r] = t;
450	}
451	}
452
453	}
454