test/jdk/java/lang/StrictMath/LogTests.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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/*
 * @test
 * @bug 8301202
 * @key randomness
 * @library /test/lib
 * @build jdk.test.lib.RandomFactory
 * @build Tests
 * @build FdlibmTranslit
 * @build LogTests
 * @run main LogTests
 * @summary Tests for StrictMath.log
 */

import jdk.test.lib.RandomFactory;

public class LogTests {
    private LogTests(){}

    public static void main(String... args) {
        int failures = 0;

        failures += testLog();
        failures += testAgainstTranslit();

        if (failures > 0) {
            System.err.println("Testing log incurred "
                               + failures + " failures.");
            throw new RuntimeException();
        }
    }

    static int testLogCase(double input, double expected) {
        return Tests.test("StrictMath.log(double)", input,
                          StrictMath::log, expected);
    }

    // Inputs where Math.log and StrictMath.log differ for at least
    // one Math.log implementation.
    static int testLog() {
        int failures = 0;

        double [][] testCases = {
            {0x1.000000089cd6fp-43, -0x1.dce2a0697a102p4},
            {0x1.0000000830698p182,  0x1.f89c7428dd67ap6},
            {0x1.0000000744b3ap632,  0x1.b611ab2bd53cep8},
            {0x1.000000037d81fp766,  0x1.0979b1dbc4a42p9},
            {0x1.000000024028p991,   0x1.577455642bb92p9},
            // Empirical worst-case points
            {0x1.0ffea3878db6bp+0,   0x1.f07a0cca521fp-5},
            {0x1.490af72a25a81p-1,  -0x1.c4bf7ae48f078p-2},
            {0x1.69e7aa6da2df5p-1,  -0x1.634508c9adfp-2},
        };

        for (double[] testCase: testCases)
            failures+=testLogCase(testCase[0], testCase[1]);

        return failures;
    }

    // Initialize shared random number generator
    private static java.util.Random random = RandomFactory.getRandom();

    /**
     * Test StrictMath.log against transliteration port of log.
     */
    private static int testAgainstTranslit() {
        int failures = 0;
        double x;

        // Test just above subnormal threshold...
        x = Double.MIN_NORMAL;
        failures += testRange(x, Math.ulp(x), 1000);

        // ... and just below subnormal threshold ...
        x = Math.nextDown(Double.MIN_NORMAL);
        failures += testRange(x, -Math.ulp(x), 1000);

        // Probe near decision points in the FDLIBM algorithm.
        double[] decisionPoints = {
            0x1.0p-1022,

            0x1.0p-20,
        };

        for (double testPoint : decisionPoints) {
            failures += testRangeMidpoint(testPoint, Math.ulp(testPoint), 1000);
        }

         x = Tests.createRandomDouble(random);

         // Make the increment twice the ulp value in case the random
         // value is near an exponent threshold. Don't worry about test
         // elements overflowing to infinity if the starting value is
         // near Double.MAX_VALUE.
         failures += testRange(x, 2.0 * Math.ulp(x), 1000);

         return failures;
    }

    private static int testRange(double start, double increment, int count) {
        int failures = 0;
        double x = start;
        for (int i = 0; i < count; i++, x += increment) {
            failures += testLogCase(x, FdlibmTranslit.log(x));
        }
        return failures;
    }

    private static int testRangeMidpoint(double midpoint, double increment, int count) {
        int failures = 0;
        double x = midpoint - increment*(count / 2) ;
        for (int i = 0; i < count; i++, x += increment) {
            failures += testLogCase(x, FdlibmTranslit.log(x));
        }
        return failures;
    }
}