Java Code Examples for sun.misc.DoubleConsts#SIGNIFICAND_WIDTH

The following examples show how to use sun.misc.DoubleConsts#SIGNIFICAND_WIDTH . You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example. You may check out the related API usage on the sidebar.
Example 1
Source File: Math.java    From openjdk-8-source with GNU General Public License v2.0 5 votes vote down vote up
/**
 * Returns the closest {@code long} to the argument, with ties
 * rounding to positive infinity.
 *
 * <p>Special cases:
 * <ul><li>If the argument is NaN, the result is 0.
 * <li>If the argument is negative infinity or any value less than or
 * equal to the value of {@code Long.MIN_VALUE}, the result is
 * equal to the value of {@code Long.MIN_VALUE}.
 * <li>If the argument is positive infinity or any value greater than or
 * equal to the value of {@code Long.MAX_VALUE}, the result is
 * equal to the value of {@code Long.MAX_VALUE}.</ul>
 *
 * @param   a   a floating-point value to be rounded to a
 *          {@code long}.
 * @return  the value of the argument rounded to the nearest
 *          {@code long} value.
 * @see     java.lang.Long#MAX_VALUE
 * @see     java.lang.Long#MIN_VALUE
 */
public static long round(double a) {
    long longBits = Double.doubleToRawLongBits(a);
    long biasedExp = (longBits & DoubleConsts.EXP_BIT_MASK)
            >> (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    long shift = (DoubleConsts.SIGNIFICAND_WIDTH - 2
            + DoubleConsts.EXP_BIAS) - biasedExp;
    if ((shift & -64) == 0) { // shift >= 0 && shift < 64
        // a is a finite number such that pow(2,-64) <= ulp(a) < 1
        long r = ((longBits & DoubleConsts.SIGNIF_BIT_MASK)
                | (DoubleConsts.SIGNIF_BIT_MASK + 1));
        if (longBits < 0) {
            r = -r;
        }
        // In the comments below each Java expression evaluates to the value
        // the corresponding mathematical expression:
        // (r) evaluates to a / ulp(a)
        // (r >> shift) evaluates to floor(a * 2)
        // ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2)
        // (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2)
        return ((r >> shift) + 1) >> 1;
    } else {
        // a is either
        // - a finite number with abs(a) < exp(2,DoubleConsts.SIGNIFICAND_WIDTH-64) < 1/2
        // - a finite number with ulp(a) >= 1 and hence a is a mathematical integer
        // - an infinity or NaN
        return (long) a;
    }
}
 
Example 2
Source File: Math.java    From AndroidComponentPlugin with Apache License 2.0 5 votes vote down vote up
/**
 * Returns the closest {@code long} to the argument, with ties
 * rounding to positive infinity.
 *
 * <p>Special cases:
 * <ul><li>If the argument is NaN, the result is 0.
 * <li>If the argument is negative infinity or any value less than or
 * equal to the value of {@code Long.MIN_VALUE}, the result is
 * equal to the value of {@code Long.MIN_VALUE}.
 * <li>If the argument is positive infinity or any value greater than or
 * equal to the value of {@code Long.MAX_VALUE}, the result is
 * equal to the value of {@code Long.MAX_VALUE}.</ul>
 *
 * @param   a   a floating-point value to be rounded to a
 *          {@code long}.
 * @return  the value of the argument rounded to the nearest
 *          {@code long} value.
 * @see     java.lang.Long#MAX_VALUE
 * @see     java.lang.Long#MIN_VALUE
 */
public static long round(double a) {
    long longBits = Double.doubleToRawLongBits(a);
    long biasedExp = (longBits & DoubleConsts.EXP_BIT_MASK)
            >> (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    long shift = (DoubleConsts.SIGNIFICAND_WIDTH - 2
            + DoubleConsts.EXP_BIAS) - biasedExp;
    if ((shift & -64) == 0) { // shift >= 0 && shift < 64
        // a is a finite number such that pow(2,-64) <= ulp(a) < 1
        long r = ((longBits & DoubleConsts.SIGNIF_BIT_MASK)
                | (DoubleConsts.SIGNIF_BIT_MASK + 1));
        if (longBits < 0) {
            r = -r;
        }
        // In the comments below each Java expression evaluates to the value
        // the corresponding mathematical expression:
        // (r) evaluates to a / ulp(a)
        // (r >> shift) evaluates to floor(a * 2)
        // ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2)
        // (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2)
        return ((r >> shift) + 1) >> 1;
    } else {
        // a is either
        // - a finite number with abs(a) < exp(2,DoubleConsts.SIGNIFICAND_WIDTH-64) < 1/2
        // - a finite number with ulp(a) >= 1 and hence a is a mathematical integer
        // - an infinity or NaN
        return (long) a;
    }
}
 
Example 3
Source File: Math.java    From jdk8u_jdk with GNU General Public License v2.0 5 votes vote down vote up
/**
 * Returns the closest {@code long} to the argument, with ties
 * rounding to positive infinity.
 *
 * <p>Special cases:
 * <ul><li>If the argument is NaN, the result is 0.
 * <li>If the argument is negative infinity or any value less than or
 * equal to the value of {@code Long.MIN_VALUE}, the result is
 * equal to the value of {@code Long.MIN_VALUE}.
 * <li>If the argument is positive infinity or any value greater than or
 * equal to the value of {@code Long.MAX_VALUE}, the result is
 * equal to the value of {@code Long.MAX_VALUE}.</ul>
 *
 * @param   a   a floating-point value to be rounded to a
 *          {@code long}.
 * @return  the value of the argument rounded to the nearest
 *          {@code long} value.
 * @see     java.lang.Long#MAX_VALUE
 * @see     java.lang.Long#MIN_VALUE
 */
public static long round(double a) {
    long longBits = Double.doubleToRawLongBits(a);
    long biasedExp = (longBits & DoubleConsts.EXP_BIT_MASK)
            >> (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    long shift = (DoubleConsts.SIGNIFICAND_WIDTH - 2
            + DoubleConsts.EXP_BIAS) - biasedExp;
    if ((shift & -64) == 0) { // shift >= 0 && shift < 64
        // a is a finite number such that pow(2,-64) <= ulp(a) < 1
        long r = ((longBits & DoubleConsts.SIGNIF_BIT_MASK)
                | (DoubleConsts.SIGNIF_BIT_MASK + 1));
        if (longBits < 0) {
            r = -r;
        }
        // In the comments below each Java expression evaluates to the value
        // the corresponding mathematical expression:
        // (r) evaluates to a / ulp(a)
        // (r >> shift) evaluates to floor(a * 2)
        // ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2)
        // (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2)
        return ((r >> shift) + 1) >> 1;
    } else {
        // a is either
        // - a finite number with abs(a) < exp(2,DoubleConsts.SIGNIFICAND_WIDTH-64) < 1/2
        // - a finite number with ulp(a) >= 1 and hence a is a mathematical integer
        // - an infinity or NaN
        return (long) a;
    }
}
 
Example 4
Source File: Math.java    From jdk8u-dev-jdk with GNU General Public License v2.0 5 votes vote down vote up
/**
 * Returns the closest {@code long} to the argument, with ties
 * rounding to positive infinity.
 *
 * <p>Special cases:
 * <ul><li>If the argument is NaN, the result is 0.
 * <li>If the argument is negative infinity or any value less than or
 * equal to the value of {@code Long.MIN_VALUE}, the result is
 * equal to the value of {@code Long.MIN_VALUE}.
 * <li>If the argument is positive infinity or any value greater than or
 * equal to the value of {@code Long.MAX_VALUE}, the result is
 * equal to the value of {@code Long.MAX_VALUE}.</ul>
 *
 * @param   a   a floating-point value to be rounded to a
 *          {@code long}.
 * @return  the value of the argument rounded to the nearest
 *          {@code long} value.
 * @see     java.lang.Long#MAX_VALUE
 * @see     java.lang.Long#MIN_VALUE
 */
public static long round(double a) {
    long longBits = Double.doubleToRawLongBits(a);
    long biasedExp = (longBits & DoubleConsts.EXP_BIT_MASK)
            >> (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    long shift = (DoubleConsts.SIGNIFICAND_WIDTH - 2
            + DoubleConsts.EXP_BIAS) - biasedExp;
    if ((shift & -64) == 0) { // shift >= 0 && shift < 64
        // a is a finite number such that pow(2,-64) <= ulp(a) < 1
        long r = ((longBits & DoubleConsts.SIGNIF_BIT_MASK)
                | (DoubleConsts.SIGNIF_BIT_MASK + 1));
        if (longBits < 0) {
            r = -r;
        }
        // In the comments below each Java expression evaluates to the value
        // the corresponding mathematical expression:
        // (r) evaluates to a / ulp(a)
        // (r >> shift) evaluates to floor(a * 2)
        // ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2)
        // (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2)
        return ((r >> shift) + 1) >> 1;
    } else {
        // a is either
        // - a finite number with abs(a) < exp(2,DoubleConsts.SIGNIFICAND_WIDTH-64) < 1/2
        // - a finite number with ulp(a) >= 1 and hence a is a mathematical integer
        // - an infinity or NaN
        return (long) a;
    }
}
 
Example 5
Source File: FpUtils.java    From javaide with GNU General Public License v3.0 5 votes vote down vote up
/**
 * Returns unbiased exponent of a <code>double</code>.
 */
public static int getExponent(double d){
    /*
     * Bitwise convert d to long, mask out exponent bits, shift
     * to the right and then subtract out double's bias adjust to
     * get true exponent value.
     */
    return (int)(((Double.doubleToRawLongBits(d) & DoubleConsts.EXP_BIT_MASK) >>
                  (DoubleConsts.SIGNIFICAND_WIDTH - 1)) - DoubleConsts.EXP_BIAS);
}
 
Example 6
Source File: Math.java    From TencentKona-8 with GNU General Public License v2.0 5 votes vote down vote up
/**
 * Returns the closest {@code long} to the argument, with ties
 * rounding to positive infinity.
 *
 * <p>Special cases:
 * <ul><li>If the argument is NaN, the result is 0.
 * <li>If the argument is negative infinity or any value less than or
 * equal to the value of {@code Long.MIN_VALUE}, the result is
 * equal to the value of {@code Long.MIN_VALUE}.
 * <li>If the argument is positive infinity or any value greater than or
 * equal to the value of {@code Long.MAX_VALUE}, the result is
 * equal to the value of {@code Long.MAX_VALUE}.</ul>
 *
 * @param   a   a floating-point value to be rounded to a
 *          {@code long}.
 * @return  the value of the argument rounded to the nearest
 *          {@code long} value.
 * @see     java.lang.Long#MAX_VALUE
 * @see     java.lang.Long#MIN_VALUE
 */
public static long round(double a) {
    long longBits = Double.doubleToRawLongBits(a);
    long biasedExp = (longBits & DoubleConsts.EXP_BIT_MASK)
            >> (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    long shift = (DoubleConsts.SIGNIFICAND_WIDTH - 2
            + DoubleConsts.EXP_BIAS) - biasedExp;
    if ((shift & -64) == 0) { // shift >= 0 && shift < 64
        // a is a finite number such that pow(2,-64) <= ulp(a) < 1
        long r = ((longBits & DoubleConsts.SIGNIF_BIT_MASK)
                | (DoubleConsts.SIGNIF_BIT_MASK + 1));
        if (longBits < 0) {
            r = -r;
        }
        // In the comments below each Java expression evaluates to the value
        // the corresponding mathematical expression:
        // (r) evaluates to a / ulp(a)
        // (r >> shift) evaluates to floor(a * 2)
        // ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2)
        // (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2)
        return ((r >> shift) + 1) >> 1;
    } else {
        // a is either
        // - a finite number with abs(a) < exp(2,DoubleConsts.SIGNIFICAND_WIDTH-64) < 1/2
        // - a finite number with ulp(a) >= 1 and hence a is a mathematical integer
        // - an infinity or NaN
        return (long) a;
    }
}
 
Example 7
Source File: FpUtils.java    From openjdk-jdk8u-backup with GNU General Public License v2.0 4 votes vote down vote up
/**
 * Returns unbiased exponent of a {@code double}; for
 * subnormal values, the number is treated as if it were
 * normalized.  That is for all finite, non-zero, positive numbers
 * <i>x</i>, <code>scalb(<i>x</i>, -ilogb(<i>x</i>))</code> is
 * always in the range [1, 2).
 * <p>
 * Special cases:
 * <ul>
 * <li> If the argument is NaN, then the result is 2<sup>30</sup>.
 * <li> If the argument is infinite, then the result is 2<sup>28</sup>.
 * <li> If the argument is zero, then the result is -(2<sup>28</sup>).
 * </ul>
 *
 * @param d floating-point number whose exponent is to be extracted
 * @return unbiased exponent of the argument.
 * @author Joseph D. Darcy
 */
public static int ilogb(double d) {
    int exponent = getExponent(d);

    switch (exponent) {
    case DoubleConsts.MAX_EXPONENT+1:       // NaN or infinity
        if( isNaN(d) )
            return (1<<30);         // 2^30
        else // infinite value
            return (1<<28);         // 2^28

    case DoubleConsts.MIN_EXPONENT-1:       // zero or subnormal
        if(d == 0.0) {
            return -(1<<28);        // -(2^28)
        }
        else {
            long transducer = Double.doubleToRawLongBits(d);

            /*
             * To avoid causing slow arithmetic on subnormals,
             * the scaling to determine when d's significand
             * is normalized is done in integer arithmetic.
             * (there must be at least one "1" bit in the
             * significand since zero has been screened out.
             */

            // isolate significand bits
            transducer &= DoubleConsts.SIGNIF_BIT_MASK;
            assert(transducer != 0L);

            // This loop is simple and functional. We might be
            // able to do something more clever that was faster;
            // e.g. number of leading zero detection on
            // (transducer << (# exponent and sign bits).
            while (transducer <
                   (1L << (DoubleConsts.SIGNIFICAND_WIDTH - 1))) {
                transducer *= 2;
                exponent--;
            }
            exponent++;
            assert( exponent >=
                    DoubleConsts.MIN_EXPONENT - (DoubleConsts.SIGNIFICAND_WIDTH-1) &&
                    exponent < DoubleConsts.MIN_EXPONENT);
            return exponent;
        }

    default:
        assert( exponent >= DoubleConsts.MIN_EXPONENT &&
                exponent <= DoubleConsts.MAX_EXPONENT);
        return exponent;
    }
}
 
Example 8
Source File: BigInteger.java    From JDKSourceCode1.8 with MIT License 4 votes vote down vote up
/**
 * Converts this BigInteger to a {@code double}.  This
 * conversion is similar to the
 * <i>narrowing primitive conversion</i> from {@code double} to
 * {@code float} as defined in section 5.1.3 of
 * <cite>The Java&trade; Language Specification</cite>:
 * if this BigInteger has too great a magnitude
 * to represent as a {@code double}, it will be converted to
 * {@link Double#NEGATIVE_INFINITY} or {@link
 * Double#POSITIVE_INFINITY} as appropriate.  Note that even when
 * the return value is finite, this conversion can lose
 * information about the precision of the BigInteger value.
 *
 * @return this BigInteger converted to a {@code double}.
 */
public double doubleValue() {
    if (signum == 0) {
        return 0.0;
    }

    int exponent = ((mag.length - 1) << 5) + bitLengthForInt(mag[0]) - 1;

    // exponent == floor(log2(abs(this))Double)
    if (exponent < Long.SIZE - 1) {
        return longValue();
    } else if (exponent > Double.MAX_EXPONENT) {
        return signum > 0 ? Double.POSITIVE_INFINITY : Double.NEGATIVE_INFINITY;
    }

    /*
     * We need the top SIGNIFICAND_WIDTH bits, including the "implicit"
     * one bit. To make rounding easier, we pick out the top
     * SIGNIFICAND_WIDTH + 1 bits, so we have one to help us round up or
     * down. twiceSignifFloor will contain the top SIGNIFICAND_WIDTH + 1
     * bits, and signifFloor the top SIGNIFICAND_WIDTH.
     *
     * It helps to consider the real number signif = abs(this) *
     * 2^(SIGNIFICAND_WIDTH - 1 - exponent).
     */
    int shift = exponent - DoubleConsts.SIGNIFICAND_WIDTH;

    long twiceSignifFloor;
    // twiceSignifFloor will be == abs().shiftRight(shift).longValue()
    // We do the shift into a long directly to improve performance.

    int nBits = shift & 0x1f;
    int nBits2 = 32 - nBits;

    int highBits;
    int lowBits;
    if (nBits == 0) {
        highBits = mag[0];
        lowBits = mag[1];
    } else {
        highBits = mag[0] >>> nBits;
        lowBits = (mag[0] << nBits2) | (mag[1] >>> nBits);
        if (highBits == 0) {
            highBits = lowBits;
            lowBits = (mag[1] << nBits2) | (mag[2] >>> nBits);
        }
    }

    twiceSignifFloor = ((highBits & LONG_MASK) << 32)
            | (lowBits & LONG_MASK);

    long signifFloor = twiceSignifFloor >> 1;
    signifFloor &= DoubleConsts.SIGNIF_BIT_MASK; // remove the implied bit

    /*
     * We round up if either the fractional part of signif is strictly
     * greater than 0.5 (which is true if the 0.5 bit is set and any lower
     * bit is set), or if the fractional part of signif is >= 0.5 and
     * signifFloor is odd (which is true if both the 0.5 bit and the 1 bit
     * are set). This is equivalent to the desired HALF_EVEN rounding.
     */
    boolean increment = (twiceSignifFloor & 1) != 0
            && ((signifFloor & 1) != 0 || abs().getLowestSetBit() < shift);
    long signifRounded = increment ? signifFloor + 1 : signifFloor;
    long bits = (long) ((exponent + DoubleConsts.EXP_BIAS))
            << (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    bits += signifRounded;
    /*
     * If signifRounded == 2^53, we'd need to set all of the significand
     * bits to zero and add 1 to the exponent. This is exactly the behavior
     * we get from just adding signifRounded to bits directly. If the
     * exponent is Double.MAX_EXPONENT, we round up (correctly) to
     * Double.POSITIVE_INFINITY.
     */
    bits |= signum & DoubleConsts.SIGN_BIT_MASK;
    return Double.longBitsToDouble(bits);
}
 
Example 9
Source File: FpUtils.java    From j2objc with Apache License 2.0 4 votes vote down vote up
/**
 * Returns unbiased exponent of a {@code double}; for
 * subnormal values, the number is treated as if it were
 * normalized.  That is for all finite, non-zero, positive numbers
 * <i>x</i>, <code>scalb(<i>x</i>, -ilogb(<i>x</i>))</code> is
 * always in the range [1, 2).
 * <p>
 * Special cases:
 * <ul>
 * <li> If the argument is NaN, then the result is 2<sup>30</sup>.
 * <li> If the argument is infinite, then the result is 2<sup>28</sup>.
 * <li> If the argument is zero, then the result is -(2<sup>28</sup>).
 * </ul>
 *
 * @param d floating-point number whose exponent is to be extracted
 * @return unbiased exponent of the argument.
 * @author Joseph D. Darcy
 */
public static int ilogb(double d) {
    int exponent = getExponent(d);

    switch (exponent) {
    case DoubleConsts.MAX_EXPONENT+1:       // NaN or infinity
        if( isNaN(d) )
            return (1<<30);         // 2^30
        else // infinite value
            return (1<<28);         // 2^28

    case DoubleConsts.MIN_EXPONENT-1:       // zero or subnormal
        if(d == 0.0) {
            return -(1<<28);        // -(2^28)
        }
        else {
            long transducer = Double.doubleToRawLongBits(d);

            /*
             * To avoid causing slow arithmetic on subnormals,
             * the scaling to determine when d's significand
             * is normalized is done in integer arithmetic.
             * (there must be at least one "1" bit in the
             * significand since zero has been screened out.
             */

            // isolate significand bits
            transducer &= DoubleConsts.SIGNIF_BIT_MASK;
            assert(transducer != 0L);

            // This loop is simple and functional. We might be
            // able to do something more clever that was faster;
            // e.g. number of leading zero detection on
            // (transducer << (# exponent and sign bits).
            while (transducer <
                   (1L << (DoubleConsts.SIGNIFICAND_WIDTH - 1))) {
                transducer *= 2;
                exponent--;
            }
            exponent++;
            assert( exponent >=
                    DoubleConsts.MIN_EXPONENT - (DoubleConsts.SIGNIFICAND_WIDTH-1) &&
                    exponent < DoubleConsts.MIN_EXPONENT);
            return exponent;
        }

    default:
        assert( exponent >= DoubleConsts.MIN_EXPONENT &&
                exponent <= DoubleConsts.MAX_EXPONENT);
        return exponent;
    }
}
 
Example 10
Source File: BigInteger.java    From openjdk-jdk8u-backup with GNU General Public License v2.0 4 votes vote down vote up
/**
 * Converts this BigInteger to a {@code double}.  This
 * conversion is similar to the
 * <i>narrowing primitive conversion</i> from {@code double} to
 * {@code float} as defined in section 5.1.3 of
 * <cite>The Java&trade; Language Specification</cite>:
 * if this BigInteger has too great a magnitude
 * to represent as a {@code double}, it will be converted to
 * {@link Double#NEGATIVE_INFINITY} or {@link
 * Double#POSITIVE_INFINITY} as appropriate.  Note that even when
 * the return value is finite, this conversion can lose
 * information about the precision of the BigInteger value.
 *
 * @return this BigInteger converted to a {@code double}.
 */
public double doubleValue() {
    if (signum == 0) {
        return 0.0;
    }

    int exponent = ((mag.length - 1) << 5) + bitLengthForInt(mag[0]) - 1;

    // exponent == floor(log2(abs(this))Double)
    if (exponent < Long.SIZE - 1) {
        return longValue();
    } else if (exponent > Double.MAX_EXPONENT) {
        return signum > 0 ? Double.POSITIVE_INFINITY : Double.NEGATIVE_INFINITY;
    }

    /*
     * We need the top SIGNIFICAND_WIDTH bits, including the "implicit"
     * one bit. To make rounding easier, we pick out the top
     * SIGNIFICAND_WIDTH + 1 bits, so we have one to help us round up or
     * down. twiceSignifFloor will contain the top SIGNIFICAND_WIDTH + 1
     * bits, and signifFloor the top SIGNIFICAND_WIDTH.
     *
     * It helps to consider the real number signif = abs(this) *
     * 2^(SIGNIFICAND_WIDTH - 1 - exponent).
     */
    int shift = exponent - DoubleConsts.SIGNIFICAND_WIDTH;

    long twiceSignifFloor;
    // twiceSignifFloor will be == abs().shiftRight(shift).longValue()
    // We do the shift into a long directly to improve performance.

    int nBits = shift & 0x1f;
    int nBits2 = 32 - nBits;

    int highBits;
    int lowBits;
    if (nBits == 0) {
        highBits = mag[0];
        lowBits = mag[1];
    } else {
        highBits = mag[0] >>> nBits;
        lowBits = (mag[0] << nBits2) | (mag[1] >>> nBits);
        if (highBits == 0) {
            highBits = lowBits;
            lowBits = (mag[1] << nBits2) | (mag[2] >>> nBits);
        }
    }

    twiceSignifFloor = ((highBits & LONG_MASK) << 32)
            | (lowBits & LONG_MASK);

    long signifFloor = twiceSignifFloor >> 1;
    signifFloor &= DoubleConsts.SIGNIF_BIT_MASK; // remove the implied bit

    /*
     * We round up if either the fractional part of signif is strictly
     * greater than 0.5 (which is true if the 0.5 bit is set and any lower
     * bit is set), or if the fractional part of signif is >= 0.5 and
     * signifFloor is odd (which is true if both the 0.5 bit and the 1 bit
     * are set). This is equivalent to the desired HALF_EVEN rounding.
     */
    boolean increment = (twiceSignifFloor & 1) != 0
            && ((signifFloor & 1) != 0 || abs().getLowestSetBit() < shift);
    long signifRounded = increment ? signifFloor + 1 : signifFloor;
    long bits = (long) ((exponent + DoubleConsts.EXP_BIAS))
            << (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    bits += signifRounded;
    /*
     * If signifRounded == 2^53, we'd need to set all of the significand
     * bits to zero and add 1 to the exponent. This is exactly the behavior
     * we get from just adding signifRounded to bits directly. If the
     * exponent is Double.MAX_EXPONENT, we round up (correctly) to
     * Double.POSITIVE_INFINITY.
     */
    bits |= signum & DoubleConsts.SIGN_BIT_MASK;
    return Double.longBitsToDouble(bits);
}
 
Example 11
Source File: BigInteger.java    From openjdk-8-source with GNU General Public License v2.0 4 votes vote down vote up
/**
 * Converts this BigInteger to a {@code double}.  This
 * conversion is similar to the
 * <i>narrowing primitive conversion</i> from {@code double} to
 * {@code float} as defined in section 5.1.3 of
 * <cite>The Java&trade; Language Specification</cite>:
 * if this BigInteger has too great a magnitude
 * to represent as a {@code double}, it will be converted to
 * {@link Double#NEGATIVE_INFINITY} or {@link
 * Double#POSITIVE_INFINITY} as appropriate.  Note that even when
 * the return value is finite, this conversion can lose
 * information about the precision of the BigInteger value.
 *
 * @return this BigInteger converted to a {@code double}.
 */
public double doubleValue() {
    if (signum == 0) {
        return 0.0;
    }

    int exponent = ((mag.length - 1) << 5) + bitLengthForInt(mag[0]) - 1;

    // exponent == floor(log2(abs(this))Double)
    if (exponent < Long.SIZE - 1) {
        return longValue();
    } else if (exponent > Double.MAX_EXPONENT) {
        return signum > 0 ? Double.POSITIVE_INFINITY : Double.NEGATIVE_INFINITY;
    }

    /*
     * We need the top SIGNIFICAND_WIDTH bits, including the "implicit"
     * one bit. To make rounding easier, we pick out the top
     * SIGNIFICAND_WIDTH + 1 bits, so we have one to help us round up or
     * down. twiceSignifFloor will contain the top SIGNIFICAND_WIDTH + 1
     * bits, and signifFloor the top SIGNIFICAND_WIDTH.
     *
     * It helps to consider the real number signif = abs(this) *
     * 2^(SIGNIFICAND_WIDTH - 1 - exponent).
     */
    int shift = exponent - DoubleConsts.SIGNIFICAND_WIDTH;

    long twiceSignifFloor;
    // twiceSignifFloor will be == abs().shiftRight(shift).longValue()
    // We do the shift into a long directly to improve performance.

    int nBits = shift & 0x1f;
    int nBits2 = 32 - nBits;

    int highBits;
    int lowBits;
    if (nBits == 0) {
        highBits = mag[0];
        lowBits = mag[1];
    } else {
        highBits = mag[0] >>> nBits;
        lowBits = (mag[0] << nBits2) | (mag[1] >>> nBits);
        if (highBits == 0) {
            highBits = lowBits;
            lowBits = (mag[1] << nBits2) | (mag[2] >>> nBits);
        }
    }

    twiceSignifFloor = ((highBits & LONG_MASK) << 32)
            | (lowBits & LONG_MASK);

    long signifFloor = twiceSignifFloor >> 1;
    signifFloor &= DoubleConsts.SIGNIF_BIT_MASK; // remove the implied bit

    /*
     * We round up if either the fractional part of signif is strictly
     * greater than 0.5 (which is true if the 0.5 bit is set and any lower
     * bit is set), or if the fractional part of signif is >= 0.5 and
     * signifFloor is odd (which is true if both the 0.5 bit and the 1 bit
     * are set). This is equivalent to the desired HALF_EVEN rounding.
     */
    boolean increment = (twiceSignifFloor & 1) != 0
            && ((signifFloor & 1) != 0 || abs().getLowestSetBit() < shift);
    long signifRounded = increment ? signifFloor + 1 : signifFloor;
    long bits = (long) ((exponent + DoubleConsts.EXP_BIAS))
            << (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    bits += signifRounded;
    /*
     * If signifRounded == 2^53, we'd need to set all of the significand
     * bits to zero and add 1 to the exponent. This is exactly the behavior
     * we get from just adding signifRounded to bits directly. If the
     * exponent is Double.MAX_EXPONENT, we round up (correctly) to
     * Double.POSITIVE_INFINITY.
     */
    bits |= signum & DoubleConsts.SIGN_BIT_MASK;
    return Double.longBitsToDouble(bits);
}
 
Example 12
Source File: BigInteger.java    From jdk8u_jdk with GNU General Public License v2.0 4 votes vote down vote up
/**
 * Converts this BigInteger to a {@code double}.  This
 * conversion is similar to the
 * <i>narrowing primitive conversion</i> from {@code double} to
 * {@code float} as defined in section 5.1.3 of
 * <cite>The Java&trade; Language Specification</cite>:
 * if this BigInteger has too great a magnitude
 * to represent as a {@code double}, it will be converted to
 * {@link Double#NEGATIVE_INFINITY} or {@link
 * Double#POSITIVE_INFINITY} as appropriate.  Note that even when
 * the return value is finite, this conversion can lose
 * information about the precision of the BigInteger value.
 *
 * @return this BigInteger converted to a {@code double}.
 */
public double doubleValue() {
    if (signum == 0) {
        return 0.0;
    }

    int exponent = ((mag.length - 1) << 5) + bitLengthForInt(mag[0]) - 1;

    // exponent == floor(log2(abs(this))Double)
    if (exponent < Long.SIZE - 1) {
        return longValue();
    } else if (exponent > Double.MAX_EXPONENT) {
        return signum > 0 ? Double.POSITIVE_INFINITY : Double.NEGATIVE_INFINITY;
    }

    /*
     * We need the top SIGNIFICAND_WIDTH bits, including the "implicit"
     * one bit. To make rounding easier, we pick out the top
     * SIGNIFICAND_WIDTH + 1 bits, so we have one to help us round up or
     * down. twiceSignifFloor will contain the top SIGNIFICAND_WIDTH + 1
     * bits, and signifFloor the top SIGNIFICAND_WIDTH.
     *
     * It helps to consider the real number signif = abs(this) *
     * 2^(SIGNIFICAND_WIDTH - 1 - exponent).
     */
    int shift = exponent - DoubleConsts.SIGNIFICAND_WIDTH;

    long twiceSignifFloor;
    // twiceSignifFloor will be == abs().shiftRight(shift).longValue()
    // We do the shift into a long directly to improve performance.

    int nBits = shift & 0x1f;
    int nBits2 = 32 - nBits;

    int highBits;
    int lowBits;
    if (nBits == 0) {
        highBits = mag[0];
        lowBits = mag[1];
    } else {
        highBits = mag[0] >>> nBits;
        lowBits = (mag[0] << nBits2) | (mag[1] >>> nBits);
        if (highBits == 0) {
            highBits = lowBits;
            lowBits = (mag[1] << nBits2) | (mag[2] >>> nBits);
        }
    }

    twiceSignifFloor = ((highBits & LONG_MASK) << 32)
            | (lowBits & LONG_MASK);

    long signifFloor = twiceSignifFloor >> 1;
    signifFloor &= DoubleConsts.SIGNIF_BIT_MASK; // remove the implied bit

    /*
     * We round up if either the fractional part of signif is strictly
     * greater than 0.5 (which is true if the 0.5 bit is set and any lower
     * bit is set), or if the fractional part of signif is >= 0.5 and
     * signifFloor is odd (which is true if both the 0.5 bit and the 1 bit
     * are set). This is equivalent to the desired HALF_EVEN rounding.
     */
    boolean increment = (twiceSignifFloor & 1) != 0
            && ((signifFloor & 1) != 0 || abs().getLowestSetBit() < shift);
    long signifRounded = increment ? signifFloor + 1 : signifFloor;
    long bits = (long) ((exponent + DoubleConsts.EXP_BIAS))
            << (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    bits += signifRounded;
    /*
     * If signifRounded == 2^53, we'd need to set all of the significand
     * bits to zero and add 1 to the exponent. This is exactly the behavior
     * we get from just adding signifRounded to bits directly. If the
     * exponent is Double.MAX_EXPONENT, we round up (correctly) to
     * Double.POSITIVE_INFINITY.
     */
    bits |= signum & DoubleConsts.SIGN_BIT_MASK;
    return Double.longBitsToDouble(bits);
}
 
Example 13
Source File: FpUtils.java    From dragonwell8_jdk with GNU General Public License v2.0 4 votes vote down vote up
/**
 * Returns unbiased exponent of a {@code double}; for
 * subnormal values, the number is treated as if it were
 * normalized.  That is for all finite, non-zero, positive numbers
 * <i>x</i>, <code>scalb(<i>x</i>, -ilogb(<i>x</i>))</code> is
 * always in the range [1, 2).
 * <p>
 * Special cases:
 * <ul>
 * <li> If the argument is NaN, then the result is 2<sup>30</sup>.
 * <li> If the argument is infinite, then the result is 2<sup>28</sup>.
 * <li> If the argument is zero, then the result is -(2<sup>28</sup>).
 * </ul>
 *
 * @param d floating-point number whose exponent is to be extracted
 * @return unbiased exponent of the argument.
 * @author Joseph D. Darcy
 */
public static int ilogb(double d) {
    int exponent = getExponent(d);

    switch (exponent) {
    case DoubleConsts.MAX_EXPONENT+1:       // NaN or infinity
        if( isNaN(d) )
            return (1<<30);         // 2^30
        else // infinite value
            return (1<<28);         // 2^28

    case DoubleConsts.MIN_EXPONENT-1:       // zero or subnormal
        if(d == 0.0) {
            return -(1<<28);        // -(2^28)
        }
        else {
            long transducer = Double.doubleToRawLongBits(d);

            /*
             * To avoid causing slow arithmetic on subnormals,
             * the scaling to determine when d's significand
             * is normalized is done in integer arithmetic.
             * (there must be at least one "1" bit in the
             * significand since zero has been screened out.
             */

            // isolate significand bits
            transducer &= DoubleConsts.SIGNIF_BIT_MASK;
            assert(transducer != 0L);

            // This loop is simple and functional. We might be
            // able to do something more clever that was faster;
            // e.g. number of leading zero detection on
            // (transducer << (# exponent and sign bits).
            while (transducer <
                   (1L << (DoubleConsts.SIGNIFICAND_WIDTH - 1))) {
                transducer *= 2;
                exponent--;
            }
            exponent++;
            assert( exponent >=
                    DoubleConsts.MIN_EXPONENT - (DoubleConsts.SIGNIFICAND_WIDTH-1) &&
                    exponent < DoubleConsts.MIN_EXPONENT);
            return exponent;
        }

    default:
        assert( exponent >= DoubleConsts.MIN_EXPONENT &&
                exponent <= DoubleConsts.MAX_EXPONENT);
        return exponent;
    }
}
 
Example 14
Source File: BigInteger.java    From hottub with GNU General Public License v2.0 4 votes vote down vote up
/**
 * Converts this BigInteger to a {@code double}.  This
 * conversion is similar to the
 * <i>narrowing primitive conversion</i> from {@code double} to
 * {@code float} as defined in section 5.1.3 of
 * <cite>The Java&trade; Language Specification</cite>:
 * if this BigInteger has too great a magnitude
 * to represent as a {@code double}, it will be converted to
 * {@link Double#NEGATIVE_INFINITY} or {@link
 * Double#POSITIVE_INFINITY} as appropriate.  Note that even when
 * the return value is finite, this conversion can lose
 * information about the precision of the BigInteger value.
 *
 * @return this BigInteger converted to a {@code double}.
 */
public double doubleValue() {
    if (signum == 0) {
        return 0.0;
    }

    int exponent = ((mag.length - 1) << 5) + bitLengthForInt(mag[0]) - 1;

    // exponent == floor(log2(abs(this))Double)
    if (exponent < Long.SIZE - 1) {
        return longValue();
    } else if (exponent > Double.MAX_EXPONENT) {
        return signum > 0 ? Double.POSITIVE_INFINITY : Double.NEGATIVE_INFINITY;
    }

    /*
     * We need the top SIGNIFICAND_WIDTH bits, including the "implicit"
     * one bit. To make rounding easier, we pick out the top
     * SIGNIFICAND_WIDTH + 1 bits, so we have one to help us round up or
     * down. twiceSignifFloor will contain the top SIGNIFICAND_WIDTH + 1
     * bits, and signifFloor the top SIGNIFICAND_WIDTH.
     *
     * It helps to consider the real number signif = abs(this) *
     * 2^(SIGNIFICAND_WIDTH - 1 - exponent).
     */
    int shift = exponent - DoubleConsts.SIGNIFICAND_WIDTH;

    long twiceSignifFloor;
    // twiceSignifFloor will be == abs().shiftRight(shift).longValue()
    // We do the shift into a long directly to improve performance.

    int nBits = shift & 0x1f;
    int nBits2 = 32 - nBits;

    int highBits;
    int lowBits;
    if (nBits == 0) {
        highBits = mag[0];
        lowBits = mag[1];
    } else {
        highBits = mag[0] >>> nBits;
        lowBits = (mag[0] << nBits2) | (mag[1] >>> nBits);
        if (highBits == 0) {
            highBits = lowBits;
            lowBits = (mag[1] << nBits2) | (mag[2] >>> nBits);
        }
    }

    twiceSignifFloor = ((highBits & LONG_MASK) << 32)
            | (lowBits & LONG_MASK);

    long signifFloor = twiceSignifFloor >> 1;
    signifFloor &= DoubleConsts.SIGNIF_BIT_MASK; // remove the implied bit

    /*
     * We round up if either the fractional part of signif is strictly
     * greater than 0.5 (which is true if the 0.5 bit is set and any lower
     * bit is set), or if the fractional part of signif is >= 0.5 and
     * signifFloor is odd (which is true if both the 0.5 bit and the 1 bit
     * are set). This is equivalent to the desired HALF_EVEN rounding.
     */
    boolean increment = (twiceSignifFloor & 1) != 0
            && ((signifFloor & 1) != 0 || abs().getLowestSetBit() < shift);
    long signifRounded = increment ? signifFloor + 1 : signifFloor;
    long bits = (long) ((exponent + DoubleConsts.EXP_BIAS))
            << (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    bits += signifRounded;
    /*
     * If signifRounded == 2^53, we'd need to set all of the significand
     * bits to zero and add 1 to the exponent. This is exactly the behavior
     * we get from just adding signifRounded to bits directly. If the
     * exponent is Double.MAX_EXPONENT, we round up (correctly) to
     * Double.POSITIVE_INFINITY.
     */
    bits |= signum & DoubleConsts.SIGN_BIT_MASK;
    return Double.longBitsToDouble(bits);
}
 
Example 15
Source File: FpUtils.java    From jdk8u_jdk with GNU General Public License v2.0 4 votes vote down vote up
/**
 * Returns unbiased exponent of a {@code double}; for
 * subnormal values, the number is treated as if it were
 * normalized.  That is for all finite, non-zero, positive numbers
 * <i>x</i>, <code>scalb(<i>x</i>, -ilogb(<i>x</i>))</code> is
 * always in the range [1, 2).
 * <p>
 * Special cases:
 * <ul>
 * <li> If the argument is NaN, then the result is 2<sup>30</sup>.
 * <li> If the argument is infinite, then the result is 2<sup>28</sup>.
 * <li> If the argument is zero, then the result is -(2<sup>28</sup>).
 * </ul>
 *
 * @param d floating-point number whose exponent is to be extracted
 * @return unbiased exponent of the argument.
 * @author Joseph D. Darcy
 */
public static int ilogb(double d) {
    int exponent = getExponent(d);

    switch (exponent) {
    case DoubleConsts.MAX_EXPONENT+1:       // NaN or infinity
        if( isNaN(d) )
            return (1<<30);         // 2^30
        else // infinite value
            return (1<<28);         // 2^28

    case DoubleConsts.MIN_EXPONENT-1:       // zero or subnormal
        if(d == 0.0) {
            return -(1<<28);        // -(2^28)
        }
        else {
            long transducer = Double.doubleToRawLongBits(d);

            /*
             * To avoid causing slow arithmetic on subnormals,
             * the scaling to determine when d's significand
             * is normalized is done in integer arithmetic.
             * (there must be at least one "1" bit in the
             * significand since zero has been screened out.
             */

            // isolate significand bits
            transducer &= DoubleConsts.SIGNIF_BIT_MASK;
            assert(transducer != 0L);

            // This loop is simple and functional. We might be
            // able to do something more clever that was faster;
            // e.g. number of leading zero detection on
            // (transducer << (# exponent and sign bits).
            while (transducer <
                   (1L << (DoubleConsts.SIGNIFICAND_WIDTH - 1))) {
                transducer *= 2;
                exponent--;
            }
            exponent++;
            assert( exponent >=
                    DoubleConsts.MIN_EXPONENT - (DoubleConsts.SIGNIFICAND_WIDTH-1) &&
                    exponent < DoubleConsts.MIN_EXPONENT);
            return exponent;
        }

    default:
        assert( exponent >= DoubleConsts.MIN_EXPONENT &&
                exponent <= DoubleConsts.MAX_EXPONENT);
        return exponent;
    }
}
 
Example 16
Source File: FpUtils.java    From openjdk-8 with GNU General Public License v2.0 4 votes vote down vote up
/**
 * Returns unbiased exponent of a {@code double}; for
 * subnormal values, the number is treated as if it were
 * normalized.  That is for all finite, non-zero, positive numbers
 * <i>x</i>, <code>scalb(<i>x</i>, -ilogb(<i>x</i>))</code> is
 * always in the range [1, 2).
 * <p>
 * Special cases:
 * <ul>
 * <li> If the argument is NaN, then the result is 2<sup>30</sup>.
 * <li> If the argument is infinite, then the result is 2<sup>28</sup>.
 * <li> If the argument is zero, then the result is -(2<sup>28</sup>).
 * </ul>
 *
 * @param d floating-point number whose exponent is to be extracted
 * @return unbiased exponent of the argument.
 * @author Joseph D. Darcy
 */
public static int ilogb(double d) {
    int exponent = getExponent(d);

    switch (exponent) {
    case DoubleConsts.MAX_EXPONENT+1:       // NaN or infinity
        if( isNaN(d) )
            return (1<<30);         // 2^30
        else // infinite value
            return (1<<28);         // 2^28

    case DoubleConsts.MIN_EXPONENT-1:       // zero or subnormal
        if(d == 0.0) {
            return -(1<<28);        // -(2^28)
        }
        else {
            long transducer = Double.doubleToRawLongBits(d);

            /*
             * To avoid causing slow arithmetic on subnormals,
             * the scaling to determine when d's significand
             * is normalized is done in integer arithmetic.
             * (there must be at least one "1" bit in the
             * significand since zero has been screened out.
             */

            // isolate significand bits
            transducer &= DoubleConsts.SIGNIF_BIT_MASK;
            assert(transducer != 0L);

            // This loop is simple and functional. We might be
            // able to do something more clever that was faster;
            // e.g. number of leading zero detection on
            // (transducer << (# exponent and sign bits).
            while (transducer <
                   (1L << (DoubleConsts.SIGNIFICAND_WIDTH - 1))) {
                transducer *= 2;
                exponent--;
            }
            exponent++;
            assert( exponent >=
                    DoubleConsts.MIN_EXPONENT - (DoubleConsts.SIGNIFICAND_WIDTH-1) &&
                    exponent < DoubleConsts.MIN_EXPONENT);
            return exponent;
        }

    default:
        assert( exponent >= DoubleConsts.MIN_EXPONENT &&
                exponent <= DoubleConsts.MAX_EXPONENT);
        return exponent;
    }
}
 
Example 17
Source File: BigInteger.java    From Java8CN with Apache License 2.0 4 votes vote down vote up
/**
 * Converts this BigInteger to a {@code double}.  This
 * conversion is similar to the
 * <i>narrowing primitive conversion</i> from {@code double} to
 * {@code float} as defined in section 5.1.3 of
 * <cite>The Java&trade; Language Specification</cite>:
 * if this BigInteger has too great a magnitude
 * to represent as a {@code double}, it will be converted to
 * {@link Double#NEGATIVE_INFINITY} or {@link
 * Double#POSITIVE_INFINITY} as appropriate.  Note that even when
 * the return value is finite, this conversion can lose
 * information about the precision of the BigInteger value.
 *
 * @return this BigInteger converted to a {@code double}.
 */
public double doubleValue() {
    if (signum == 0) {
        return 0.0;
    }

    int exponent = ((mag.length - 1) << 5) + bitLengthForInt(mag[0]) - 1;

    // exponent == floor(log2(abs(this))Double)
    if (exponent < Long.SIZE - 1) {
        return longValue();
    } else if (exponent > Double.MAX_EXPONENT) {
        return signum > 0 ? Double.POSITIVE_INFINITY : Double.NEGATIVE_INFINITY;
    }

    /*
     * We need the top SIGNIFICAND_WIDTH bits, including the "implicit"
     * one bit. To make rounding easier, we pick out the top
     * SIGNIFICAND_WIDTH + 1 bits, so we have one to help us round up or
     * down. twiceSignifFloor will contain the top SIGNIFICAND_WIDTH + 1
     * bits, and signifFloor the top SIGNIFICAND_WIDTH.
     *
     * It helps to consider the real number signif = abs(this) *
     * 2^(SIGNIFICAND_WIDTH - 1 - exponent).
     */
    int shift = exponent - DoubleConsts.SIGNIFICAND_WIDTH;

    long twiceSignifFloor;
    // twiceSignifFloor will be == abs().shiftRight(shift).longValue()
    // We do the shift into a long directly to improve performance.

    int nBits = shift & 0x1f;
    int nBits2 = 32 - nBits;

    int highBits;
    int lowBits;
    if (nBits == 0) {
        highBits = mag[0];
        lowBits = mag[1];
    } else {
        highBits = mag[0] >>> nBits;
        lowBits = (mag[0] << nBits2) | (mag[1] >>> nBits);
        if (highBits == 0) {
            highBits = lowBits;
            lowBits = (mag[1] << nBits2) | (mag[2] >>> nBits);
        }
    }

    twiceSignifFloor = ((highBits & LONG_MASK) << 32)
            | (lowBits & LONG_MASK);

    long signifFloor = twiceSignifFloor >> 1;
    signifFloor &= DoubleConsts.SIGNIF_BIT_MASK; // remove the implied bit

    /*
     * We round up if either the fractional part of signif is strictly
     * greater than 0.5 (which is true if the 0.5 bit is set and any lower
     * bit is set), or if the fractional part of signif is >= 0.5 and
     * signifFloor is odd (which is true if both the 0.5 bit and the 1 bit
     * are set). This is equivalent to the desired HALF_EVEN rounding.
     */
    boolean increment = (twiceSignifFloor & 1) != 0
            && ((signifFloor & 1) != 0 || abs().getLowestSetBit() < shift);
    long signifRounded = increment ? signifFloor + 1 : signifFloor;
    long bits = (long) ((exponent + DoubleConsts.EXP_BIAS))
            << (DoubleConsts.SIGNIFICAND_WIDTH - 1);
    bits += signifRounded;
    /*
     * If signifRounded == 2^53, we'd need to set all of the significand
     * bits to zero and add 1 to the exponent. This is exactly the behavior
     * we get from just adding signifRounded to bits directly. If the
     * exponent is Double.MAX_EXPONENT, we round up (correctly) to
     * Double.POSITIVE_INFINITY.
     */
    bits |= signum & DoubleConsts.SIGN_BIT_MASK;
    return Double.longBitsToDouble(bits);
}
 
Example 18
Source File: FpUtils.java    From java-n-IDE-for-Android with Apache License 2.0 4 votes vote down vote up
/**
 * Returns unbiased exponent of a <code>double</code>; for
 * subnormal values, the number is treated as if it were
 * normalized.  That is for all finite, non-zero, positive numbers
 * <i>x</i>, <code>scalb(<i>x</i>, -ilogb(<i>x</i>))</code> is
 * always in the range [1, 2).
 * <p>
 * Special cases:
 * <ul>
 * <li> If the argument is NaN, then the result is 2<sup>30</sup>.
 * <li> If the argument is infinite, then the result is 2<sup>28</sup>.
 * <li> If the argument is zero, then the result is -(2<sup>28</sup>).
 * </ul>
 *
 * @param d floating-point number whose exponent is to be extracted
 * @return unbiased exponent of the argument.
 * @author Joseph D. Darcy
 */
public static int ilogb(double d) {
    int exponent = getExponent(d);

    switch (exponent) {
    case DoubleConsts.MAX_EXPONENT+1:       // NaN or infinity
        if( isNaN(d) )
            return (1<<30);         // 2^30
        else // infinite value
            return (1<<28);         // 2^28
    // break;

    case DoubleConsts.MIN_EXPONENT-1:       // zero or subnormal
        if(d == 0.0) {
            return -(1<<28);        // -(2^28)
        }
        else {
            long transducer = Double.doubleToRawLongBits(d);

            /*
             * To avoid causing slow arithmetic on subnormals,
             * the scaling to determine when d's significand
             * is normalized is done in integer arithmetic.
             * (there must be at least one "1" bit in the
             * significand since zero has been screened out.
             */

            // isolate significand bits
            transducer &= DoubleConsts.SIGNIF_BIT_MASK;
            assert(transducer != 0L);

            // This loop is simple and functional. We might be
            // able to do something more clever that was faster;
            // e.g. number of leading zero detection on
            // (transducer << (# exponent and sign bits).
            while (transducer <
                   (1L << (DoubleConsts.SIGNIFICAND_WIDTH - 1))) {
                transducer *= 2;
                exponent--;
            }
            exponent++;
            assert( exponent >=
                    DoubleConsts.MIN_EXPONENT - (DoubleConsts.SIGNIFICAND_WIDTH-1) &&
                    exponent < DoubleConsts.MIN_EXPONENT);
            return exponent;
        }
    // break;

    default:
        assert( exponent >= DoubleConsts.MIN_EXPONENT &&
                exponent <= DoubleConsts.MAX_EXPONENT);
        return exponent;
    // break;
    }
}
 
Example 19
Source File: Math.java    From JDKSourceCode1.8 with MIT License 3 votes vote down vote up
/**
 * Returns the unbiased exponent used in the representation of a
 * {@code double}.  Special cases:
 *
 * <ul>
 * <li>If the argument is NaN or infinite, then the result is
 * {@link Double#MAX_EXPONENT} + 1.
 * <li>If the argument is zero or subnormal, then the result is
 * {@link Double#MIN_EXPONENT} -1.
 * </ul>
 * @param d a {@code double} value
 * @return the unbiased exponent of the argument
 * @since 1.6
 */
public static int getExponent(double d) {
    /*
     * Bitwise convert d to long, mask out exponent bits, shift
     * to the right and then subtract out double's bias adjust to
     * get true exponent value.
     */
    return (int)(((Double.doubleToRawLongBits(d) & DoubleConsts.EXP_BIT_MASK) >>
                  (DoubleConsts.SIGNIFICAND_WIDTH - 1)) - DoubleConsts.EXP_BIAS);
}
 
Example 20
Source File: Math.java    From openjdk-8-source with GNU General Public License v2.0 3 votes vote down vote up
/**
 * Returns the unbiased exponent used in the representation of a
 * {@code double}.  Special cases:
 *
 * <ul>
 * <li>If the argument is NaN or infinite, then the result is
 * {@link Double#MAX_EXPONENT} + 1.
 * <li>If the argument is zero or subnormal, then the result is
 * {@link Double#MIN_EXPONENT} -1.
 * </ul>
 * @param d a {@code double} value
 * @return the unbiased exponent of the argument
 * @since 1.6
 */
public static int getExponent(double d) {
    /*
     * Bitwise convert d to long, mask out exponent bits, shift
     * to the right and then subtract out double's bias adjust to
     * get true exponent value.
     */
    return (int)(((Double.doubleToRawLongBits(d) & DoubleConsts.EXP_BIT_MASK) >>
                  (DoubleConsts.SIGNIFICAND_WIDTH - 1)) - DoubleConsts.EXP_BIAS);
}