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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

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 *

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 * 2 along with this work; if not, write to the Free Software Foundation,

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 */

/*

 * @test

 * @bug 4074599 4939441

 * @summary Tests for {Math, StrictMath}.log10

 * @author Joseph D. Darcy

 */

import sun.misc.DoubleConsts;

public class Log10Tests {

    private Log10Tests(){}

    static final double infinityD = Double.POSITIVE_INFINITY;

    static final double NaNd = Double.NaN;

    static final double LN_10 = StrictMath.log(10.0);

    // Initialize shared random number generator

    static java.util.Random rand = new java.util.Random(0L);

    static int testLog10Case(double input, double expected) {

        int failures=0;

        failures+=Tests.test("Math.log10(double)", input,

                             Math.log10(input), expected);

        failures+=Tests.test("StrictMath.log10(double)", input,

                             StrictMath.log10(input), expected);

        return failures;

    }

    static int testLog10() {

        int failures = 0;

        double [][] testCases = {

            {Double.NaN,                NaNd},

            {Double.longBitsToDouble(0x7FF0000000000001L),      NaNd},

            {Double.longBitsToDouble(0xFFF0000000000001L),      NaNd},

            {Double.longBitsToDouble(0x7FF8555555555555L),      NaNd},

            {Double.longBitsToDouble(0xFFF8555555555555L),      NaNd},

            {Double.longBitsToDouble(0x7FFFFFFFFFFFFFFFL),      NaNd},

            {Double.longBitsToDouble(0xFFFFFFFFFFFFFFFFL),      NaNd},

            {Double.longBitsToDouble(0x7FFDeadBeef00000L),      NaNd},

            {Double.longBitsToDouble(0xFFFDeadBeef00000L),      NaNd},

            {Double.longBitsToDouble(0x7FFCafeBabe00000L),      NaNd},

            {Double.longBitsToDouble(0xFFFCafeBabe00000L),      NaNd},

            {Double.NEGATIVE_INFINITY,  NaNd},

            {-8.0,                      NaNd},

            {-1.0,                      NaNd},

            {-DoubleConsts.MIN_NORMAL,  NaNd},

            {-Double.MIN_VALUE,         NaNd},

            {-0.0,                      -infinityD},

            {+0.0,                      -infinityD},

            {+1.0,                      0.0},

            {Double.POSITIVE_INFINITY,  infinityD},

        };

        // Test special cases

        for(int i = 0; i < testCases.length; i++) {

            failures += testLog10Case(testCases[i][0],

                                          testCases[i][1]);

        }

        // Test log10(10^n) == n for integer n; 10^n, n < 0 is not

        // exactly representable as a floating-point value -- up to

        // 10^22 can be represented exactly

        double testCase = 1.0;

        for(int i = 0; i < 23; i++) {

            failures += testLog10Case(testCase, i);

            testCase *= 10.0;

        }

        // Test for gross inaccuracy by comparing to log; should be

        // within a few ulps of log(x)/log(10)

        for(int i = 0; i < 10000; i++) {

            double input = Double.longBitsToDouble(rand.nextLong());

            if(! Double.isFinite(input))

                continue; // avoid testing NaN and infinite values

            else {

                input = Math.abs(input);

                double expected = StrictMath.log(input)/LN_10;

                if( ! Double.isFinite(expected))

                    continue; // if log(input) overflowed, try again

                else {

                    double result;

                    if( Math.abs(((result=Math.log10(input)) - expected)/Math.ulp(expected)) > 3) {

                        failures++;

                        System.err.println("For input " + input +

                                           ", Math.log10 was more than 3 ulps different from " +

                                           "log(input)/log(10): log10(input) = " + result +

                                           "\tlog(input)/log(10) = " + expected);

                    }

                    if( Math.abs(((result=StrictMath.log10(input)) - expected)/Math.ulp(expected)) > 3) {

                        failures++;

                        System.err.println("For input " + input +

                                           ", StrictMath.log10 was more than 3 ulps different from " +

                                           "log(input)/log(10): log10(input) = " + result +

                                           "\tlog(input)/log(10) = " + expected);

                    }

                }

            }

        }

        // Test for accuracy and monotonicity near log10(1.0).  From

        // the Taylor expansion of log,

        // log10(1+z) ~= (z -(z^2)/2)/LN_10;

        {

            double neighbors[] =        new double[40];

            double neighborsStrict[] =  new double[40];

            double z = Double.NaN;

            // Test inputs greater than 1.0.

            neighbors[0] =              Math.log10(1.0);

            neighborsStrict[0] =        StrictMath.log10(1.0);

            double input[] =  new double[40];

            int half = input.length/2;

            // Initialize input to the 40 consecutive double values

            // "centered" at 1.0.

            double up = Double.NaN;

            double down = Double.NaN;

            for(int i = 0; i < half; i++) {

                if (i == 0) {

                    input[half] = 1.0;

                    up   = Math.nextUp(1.0);

                    down = Math.nextDown(1.0);

                } else {

                    input[half + i] = up;

                    input[half - i] = down;

                    up   = Math.nextUp(up);

                    down = Math.nextDown(down);

                }

            }

            input[0] = Math.nextDown(input[1]);

            for(int i = 0; i < neighbors.length; i++) {

                neighbors[i] =          Math.log10(input[i]);

                neighborsStrict[i] =    StrictMath.log10(input[i]);

                // Test accuracy.

                z = input[i] - 1.0;

                double expected = (z - (z*z)*0.5)/LN_10;

                if ( Math.abs(neighbors[i] - expected ) > 3*Math.ulp(expected) ) {

                    failures++;

                    System.err.println("For input near 1.0 " + input[i] +

                                       ", Math.log10(1+z) was more than 3 ulps different from " +

                                       "(z-(z^2)/2)/ln(10): log10(input) = " + neighbors[i] +

                                       "\texpected about = " + expected);

                }

                if ( Math.abs(neighborsStrict[i] - expected ) > 3*Math.ulp(expected) ) {

                    failures++;

                    System.err.println("For input near 1.0 " + input[i] +

                                       ", StrictMath.log10(1+z) was more than 3 ulps different from " +

                                       "(z-(z^2)/2)/ln(10): log10(input) = " + neighborsStrict[i] +

                                       "\texpected about = " + expected);

                }

                // Test monotonicity

                if( i > 0) {

                    if( neighbors[i-1] > neighbors[i] ) {

                        failures++;

                        System.err.println("Monotonicity failure for Math.log10  at " + input[i] +

                                           " and prior value.");

                    }

                    if( neighborsStrict[i-1] > neighborsStrict[i] ) {

                        failures++;

                        System.err.println("Monotonicity failure for StrictMath.log10  at " + input[i] +

                                           " and prior value.");

                    }

                }

            }

        }

        return failures;

    }

    public static void main(String argv[]) {

        int failures = 0;

        failures += testLog10();

        if (failures > 0) {

            System.err.println("Testing log10 incurred "

                               + failures + " failures.");

            throw new RuntimeException();

        }

    }

}