1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  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
  13  * accompanied this code).
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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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  23 
  24 /*
  25  * @test
  26  * @bug 4851638 4939441
  27  * @summary Tests for {Math, StrictMath}.hypot
  28  * @author Joseph D. Darcy
  29  */
  30 
  31 public class HypotTests {
  32     private HypotTests(){}
  33 
  34     static final double infinityD = Double.POSITIVE_INFINITY;
  35     static final double NaNd      = Double.NaN;
  36 
  37     /**
  38      * Given integers m and n, assuming m < n, the triple (n^2 - m^2,
  39      * 2mn, and n^2 + m^2) is a Pythagorean triple with a^2 + b^2 =
  40      * c^2.  This methods returns a long array holding the Pythagorean
  41      * triple corresponding to the inputs.
  42      */
  43     static long [] pythagoreanTriple(int m, int n) {
  44         long M = m;
  45         long N = n;
  46         long result[] = new long[3];
  47 
  48 
  49         result[0] = Math.abs(M*M - N*N);
  50         result[1] = Math.abs(2*M*N);
  51         result[2] = Math.abs(M*M + N*N);
  52 
  53         return result;
  54     }
  55 
  56     static int testHypot() {
  57         int failures = 0;
  58 
  59         double [][] testCases = {
  60             // Special cases
  61             {infinityD,         infinityD,              infinityD},
  62             {infinityD,         0.0,                    infinityD},
  63             {infinityD,         1.0,                    infinityD},
  64             {infinityD,         NaNd,                   infinityD},
  65             {NaNd,              NaNd,                   NaNd},
  66             {0.0,               NaNd,                   NaNd},
  67             {1.0,               NaNd,                   NaNd},
  68             {Double.longBitsToDouble(0x7FF0000000000001L),      1.0,    NaNd},
  69             {Double.longBitsToDouble(0xFFF0000000000001L),      1.0,    NaNd},
  70             {Double.longBitsToDouble(0x7FF8555555555555L),      1.0,    NaNd},
  71             {Double.longBitsToDouble(0xFFF8555555555555L),      1.0,    NaNd},
  72             {Double.longBitsToDouble(0x7FFFFFFFFFFFFFFFL),      1.0,    NaNd},
  73             {Double.longBitsToDouble(0xFFFFFFFFFFFFFFFFL),      1.0,    NaNd},
  74             {Double.longBitsToDouble(0x7FFDeadBeef00000L),      1.0,    NaNd},
  75             {Double.longBitsToDouble(0xFFFDeadBeef00000L),      1.0,    NaNd},
  76             {Double.longBitsToDouble(0x7FFCafeBabe00000L),      1.0,    NaNd},
  77             {Double.longBitsToDouble(0xFFFCafeBabe00000L),      1.0,    NaNd},
  78         };
  79 
  80         for(int i = 0; i < testCases.length; i++) {
  81             failures += testHypotCase(testCases[i][0], testCases[i][1],
  82                                       testCases[i][2]);
  83         }
  84 
  85         // Verify hypot(x, 0.0) is close to x over the entire exponent
  86         // range.
  87         for(int i = DoubleConsts.MIN_SUB_EXPONENT;
  88             i <= Double.MAX_EXPONENT;
  89             i++) {
  90             double input = Math.scalb(2, i);
  91             failures += testHypotCase(input, 0.0, input);
  92         }
  93 
  94 
  95         // Test Pythagorean triples
  96 
  97         // Small ones
  98         for(int m = 1; m < 10; m++) {
  99             for(int n = m+1; n < 11; n++) {
 100                 long [] result = pythagoreanTriple(m, n);
 101                 failures += testHypotCase(result[0], result[1], result[2]);
 102             }
 103         }
 104 
 105         // Big ones
 106         for(int m = 100000; m < 100100; m++) {
 107             for(int n = m+100000; n < 200200; n++) {
 108                 long [] result = pythagoreanTriple(m, n);
 109                 failures += testHypotCase(result[0], result[1], result[2]);
 110             }
 111         }
 112 
 113         // Approaching overflow tests
 114 
 115         /*
 116          * Create a random value r with an large-ish exponent.  The
 117          * result of hypot(3*r, 4*r) should be approximately 5*r. (The
 118          * computation of 4*r is exact since it just changes the
 119          * exponent).  While the exponent of r is less than or equal
 120          * to (MAX_EXPONENT - 3), the computation should not overflow.
 121          */
 122         java.util.Random rand = new java.util.Random();
 123         for(int i = 0; i < 1000; i++) {
 124             double d = rand.nextDouble();
 125             // Scale d to have an exponent equal to MAX_EXPONENT -15
 126             d = Math.scalb(d, Double.MAX_EXPONENT
 127                                  -15 - Tests.ilogb(d));
 128             for(int j = 0; j <= 13; j += 1) {
 129                 failures += testHypotCase(3*d, 4*d, 5*d, 2.5);
 130                 d *= 2.0; // increase exponent by 1
 131             }
 132         }
 133 
 134         // Test for monotonicity failures.  Fix one argument and test
 135         // two numbers before and two numbers after each chosen value;
 136         // i.e.
 137         //
 138         // pcNeighbors[] =
 139         // {nextDown(nextDown(pc)),
 140         // nextDown(pc),
 141         // pc,
 142         // nextUp(pc),
 143         // nextUp(nextUp(pc))}
 144         //
 145         // and we test that hypot(pcNeighbors[i]) <= hypot(pcNeighbors[i+1])
 146         {
 147             double pcNeighbors[] = new double[5];
 148             double pcNeighborsHypot[] = new double[5];
 149             double pcNeighborsStrictHypot[] = new double[5];
 150 
 151 
 152             for(int i = -18; i <= 18; i++) {
 153                 double pc = Math.scalb(1.0, i);
 154 
 155                 pcNeighbors[2] = pc;
 156                 pcNeighbors[1] = Math.nextDown(pc);
 157                 pcNeighbors[0] = Math.nextDown(pcNeighbors[1]);
 158                 pcNeighbors[3] = Math.nextUp(pc);
 159                 pcNeighbors[4] = Math.nextUp(pcNeighbors[3]);
 160 
 161                 for(int j = 0; j < pcNeighbors.length; j++) {
 162                     pcNeighborsHypot[j]       =       Math.hypot(2.0, pcNeighbors[j]);
 163                     pcNeighborsStrictHypot[j] = StrictMath.hypot(2.0, pcNeighbors[j]);
 164                 }
 165 
 166                 for(int j = 0; j < pcNeighborsHypot.length-1; j++) {
 167                     if(pcNeighborsHypot[j] >  pcNeighborsHypot[j+1] ) {
 168                         failures++;
 169                         System.err.println("Monotonicity failure for Math.hypot on " +
 170                                           pcNeighbors[j] + " and "  +
 171                                           pcNeighbors[j+1] + "\n\treturned " +
 172                                           pcNeighborsHypot[j] + " and " +
 173                                           pcNeighborsHypot[j+1] );
 174                     }
 175 
 176                     if(pcNeighborsStrictHypot[j] >  pcNeighborsStrictHypot[j+1] ) {
 177                         failures++;
 178                         System.err.println("Monotonicity failure for StrictMath.hypot on " +
 179                                           pcNeighbors[j] + " and "  +
 180                                           pcNeighbors[j+1] + "\n\treturned " +
 181                                           pcNeighborsStrictHypot[j] + " and " +
 182                                           pcNeighborsStrictHypot[j+1] );
 183                     }
 184 
 185 
 186                 }
 187 
 188             }
 189         }
 190 
 191 
 192         return failures;
 193     }
 194 
 195     static int testHypotCase(double input1, double input2, double expected) {
 196         return testHypotCase(input1,input2, expected, 1);
 197     }
 198 
 199     static int testHypotCase(double input1, double input2, double expected,
 200                              double ulps) {
 201         int failures = 0;
 202         if (expected < 0.0) {
 203             throw new AssertionError("Result of hypot must be greater than " +
 204                                      "or equal to zero");
 205         }
 206 
 207         // Test Math and StrictMath methods with no inputs negated,
 208         // each input negated singly, and both inputs negated.  Also
 209         // test inputs in reversed order.
 210 
 211         for(int i = -1; i <= 1; i+=2) {
 212             for(int j = -1; j <= 1; j+=2) {
 213                 double x = i * input1;
 214                 double y = j * input2;
 215                 failures += Tests.testUlpDiff("Math.hypot", x, y,
 216                                               Math.hypot(x, y), expected, ulps);
 217                 failures += Tests.testUlpDiff("Math.hypot", y, x,
 218                                               Math.hypot(y, x ), expected, ulps);
 219 
 220                 failures += Tests.testUlpDiff("StrictMath.hypot", x, y,
 221                                               StrictMath.hypot(x, y), expected, ulps);
 222                 failures += Tests.testUlpDiff("StrictMath.hypot", y, x,
 223                                               StrictMath.hypot(y, x), expected, ulps);
 224             }
 225         }
 226 
 227         return failures;
 228     }
 229 
 230     public static void main(String argv[]) {
 231         int failures = 0;
 232 
 233         failures += testHypot();
 234 
 235         if (failures > 0) {
 236             System.err.println("Testing the hypot incurred "
 237                                + failures + " failures.");
 238             throw new RuntimeException();
 239         }
 240     }
 241 
 242 }