Log10Tests.java revision 6264:a68090f0dc1a 
1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
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22 */
23
24/*
25 * @test
26 * @bug 4074599 4939441
27 * @summary Tests for {Math, StrictMath}.log10
28 * @author Joseph D. Darcy
29 */
30
31import sun.misc.DoubleConsts;
32
33public class Log10Tests {
34    private Log10Tests(){}
35
36    static final double infinityD = Double.POSITIVE_INFINITY;
37    static final double NaNd = Double.NaN;
38    static final double LN_10 = StrictMath.log(10.0);
39
40    // Initialize shared random number generator
41    static java.util.Random rand = new java.util.Random(0L);
42
43    static int testLog10Case(double input, double expected) {
44        int failures=0;
45
46        failures+=Tests.test("Math.log10(double)", input,
47                             Math.log10(input), expected);
48
49        failures+=Tests.test("StrictMath.log10(double)", input,
50                             StrictMath.log10(input), expected);
51
52        return failures;
53    }
54
55    static int testLog10() {
56        int failures = 0;
57
58        double [][] testCases = {
59            {Double.NaN,                NaNd},
60            {Double.longBitsToDouble(0x7FF0000000000001L),      NaNd},
61            {Double.longBitsToDouble(0xFFF0000000000001L),      NaNd},
62            {Double.longBitsToDouble(0x7FF8555555555555L),      NaNd},
63            {Double.longBitsToDouble(0xFFF8555555555555L),      NaNd},
64            {Double.longBitsToDouble(0x7FFFFFFFFFFFFFFFL),      NaNd},
65            {Double.longBitsToDouble(0xFFFFFFFFFFFFFFFFL),      NaNd},
66            {Double.longBitsToDouble(0x7FFDeadBeef00000L),      NaNd},
67            {Double.longBitsToDouble(0xFFFDeadBeef00000L),      NaNd},
68            {Double.longBitsToDouble(0x7FFCafeBabe00000L),      NaNd},
69            {Double.longBitsToDouble(0xFFFCafeBabe00000L),      NaNd},
70            {Double.NEGATIVE_INFINITY,  NaNd},
71            {-8.0,                      NaNd},
72            {-1.0,                      NaNd},
73            {-DoubleConsts.MIN_NORMAL,  NaNd},
74            {-Double.MIN_VALUE,         NaNd},
75            {-0.0,                      -infinityD},
76            {+0.0,                      -infinityD},
77            {+1.0,                      0.0},
78            {Double.POSITIVE_INFINITY,  infinityD},
79        };
80
81        // Test special cases
82        for(int i = 0; i < testCases.length; i++) {
83            failures += testLog10Case(testCases[i][0],
84                                          testCases[i][1]);
85        }
86
87        // Test log10(10^n) == n for integer n; 10^n, n < 0 is not
88        // exactly representable as a floating-point value -- up to
89        // 10^22 can be represented exactly
90        double testCase = 1.0;
91        for(int i = 0; i < 23; i++) {
92            failures += testLog10Case(testCase, i);
93            testCase *= 10.0;
94        }
95
96        // Test for gross inaccuracy by comparing to log; should be
97        // within a few ulps of log(x)/log(10)
98        for(int i = 0; i < 10000; i++) {
99            double input = Double.longBitsToDouble(rand.nextLong());
100            if(! Double.isFinite(input))
101                continue; // avoid testing NaN and infinite values
102            else {
103                input = Math.abs(input);
104
105                double expected = StrictMath.log(input)/LN_10;
106                if( ! Double.isFinite(expected))
107                    continue; // if log(input) overflowed, try again
108                else {
109                    double result;
110
111                    if( Math.abs(((result=Math.log10(input)) - expected)/Math.ulp(expected)) > 3) {
112                        failures++;
113                        System.err.println("For input " + input +
114                                           ", Math.log10 was more than 3 ulps different from " +
115                                           "log(input)/log(10): log10(input) = " + result +
116                                           "\tlog(input)/log(10) = " + expected);
117                    }
118
119                    if( Math.abs(((result=StrictMath.log10(input)) - expected)/Math.ulp(expected)) > 3) {
120                        failures++;
121                        System.err.println("For input " + input +
122                                           ", StrictMath.log10 was more than 3 ulps different from " +
123                                           "log(input)/log(10): log10(input) = " + result +
124                                           "\tlog(input)/log(10) = " + expected);
125                    }
126
127
128                }
129            }
130        }
131
132        // Test for accuracy and monotonicity near log10(1.0).  From
133        // the Taylor expansion of log,
134        // log10(1+z) ~= (z -(z^2)/2)/LN_10;
135        {
136            double neighbors[] =        new double[40];
137            double neighborsStrict[] =  new double[40];
138            double z = Double.NaN;
139
140            // Test inputs greater than 1.0.
141            neighbors[0] =              Math.log10(1.0);
142            neighborsStrict[0] =        StrictMath.log10(1.0);
143
144            double input[] =  new double[40];
145            int half = input.length/2;
146
147
148            // Initialize input to the 40 consecutive double values
149            // "centered" at 1.0.
150            double up = Double.NaN;
151            double down = Double.NaN;
152            for(int i = 0; i < half; i++) {
153                if (i == 0) {
154                    input[half] = 1.0;
155                    up   = Math.nextUp(1.0);
156                    down = Math.nextDown(1.0);
157                } else {
158                    input[half + i] = up;
159                    input[half - i] = down;
160                    up   = Math.nextUp(up);
161                    down = Math.nextDown(down);
162                }
163            }
164            input[0] = Math.nextDown(input[1]);
165
166            for(int i = 0; i < neighbors.length; i++) {
167                neighbors[i] =          Math.log10(input[i]);
168                neighborsStrict[i] =    StrictMath.log10(input[i]);
169
170                // Test accuracy.
171                z = input[i] - 1.0;
172                double expected = (z - (z*z)*0.5)/LN_10;
173                if ( Math.abs(neighbors[i] - expected ) > 3*Math.ulp(expected) ) {
174                    failures++;
175                    System.err.println("For input near 1.0 " + input[i] +
176                                       ", Math.log10(1+z) was more than 3 ulps different from " +
177                                       "(z-(z^2)/2)/ln(10): log10(input) = " + neighbors[i] +
178                                       "\texpected about = " + expected);
179                }
180
181                if ( Math.abs(neighborsStrict[i] - expected ) > 3*Math.ulp(expected) ) {
182                    failures++;
183                    System.err.println("For input near 1.0 " + input[i] +
184                                       ", StrictMath.log10(1+z) was more than 3 ulps different from " +
185                                       "(z-(z^2)/2)/ln(10): log10(input) = " + neighborsStrict[i] +
186                                       "\texpected about = " + expected);
187                }
188
189                // Test monotonicity
190                if( i > 0) {
191                    if( neighbors[i-1] > neighbors[i] ) {
192                        failures++;
193                        System.err.println("Monotonicity failure for Math.log10  at " + input[i] +
194                                           " and prior value.");
195                    }
196
197                    if( neighborsStrict[i-1] > neighborsStrict[i] ) {
198                        failures++;
199                        System.err.println("Monotonicity failure for StrictMath.log10  at " + input[i] +
200                                           " and prior value.");
201                    }
202                }
203            }
204
205        }
206
207        return failures;
208    }
209
210    public static void main(String argv[]) {
211        int failures = 0;
212
213        failures += testLog10();
214
215        if (failures > 0) {
216            System.err.println("Testing log10 incurred "
217                               + failures + " failures.");
218            throw new RuntimeException();
219        }
220    }
221
222}
223