Python math.ldexp() Examples

The following are code examples for showing how to use math.ldexp(). They are extracted from open source Python projects. You can vote up the examples you like or vote down the ones you don't like. You can also save this page to your account.

Example 1
Project: zippy   Author: securesystemslab   File: test_float.py    (license) View Source Project 6 votes vote down vote up
def test_roundtrip(self):
        def roundtrip(x):
            return fromHex(toHex(x))

        for x in [NAN, INF, self.MAX, self.MIN, self.MIN-self.TINY, self.TINY, 0.0]:
            self.identical(x, roundtrip(x))
            self.identical(-x, roundtrip(-x))

        # fromHex(toHex(x)) should exactly recover x, for any non-NaN float x.
        import random
        for i in range(10000):
            e = random.randrange(-1200, 1200)
            m = random.random()
            s = random.choice([1.0, -1.0])
            try:
                x = s*ldexp(m, e)
            except OverflowError:
                pass
            else:
                self.identical(x, fromHex(toHex(x))) 
Example 2
Project: oil   Author: oilshell   File: test_float.py    (license) View Source Project 6 votes vote down vote up
def test_roundtrip(self):
        def roundtrip(x):
            return fromHex(toHex(x))

        for x in [NAN, INF, self.MAX, self.MIN, self.MIN-self.TINY, self.TINY, 0.0]:
            self.identical(x, roundtrip(x))
            self.identical(-x, roundtrip(-x))

        # fromHex(toHex(x)) should exactly recover x, for any non-NaN float x.
        import random
        for i in xrange(10000):
            e = random.randrange(-1200, 1200)
            m = random.random()
            s = random.choice([1.0, -1.0])
            try:
                x = s*ldexp(m, e)
            except OverflowError:
                pass
            else:
                self.identical(x, fromHex(toHex(x))) 
Example 3
Project: oil   Author: oilshell   File: test_random.py    (license) View Source Project 6 votes vote down vote up
def test_strong_reference_implementation(self):
        # Like test_referenceImplementation, but checks for exact bit-level
        # equality.  This should pass on any box where C double contains
        # at least 53 bits of precision (the underlying algorithm suffers
        # no rounding errors -- all results are exact).
        from math import ldexp

        expected = [0x0eab3258d2231fL,
                    0x1b89db315277a5L,
                    0x1db622a5518016L,
                    0x0b7f9af0d575bfL,
                    0x029e4c4db82240L,
                    0x04961892f5d673L,
                    0x02b291598e4589L,
                    0x11388382c15694L,
                    0x02dad977c9e1feL,
                    0x191d96d4d334c6L]
        self.gen.seed(61731L + (24903L<<32) + (614L<<64) + (42143L<<96))
        actual = self.randomlist(2000)[-10:]
        for a, e in zip(actual, expected):
            self.assertEqual(long(ldexp(a, 53)), e) 
Example 4
Project: python2-tracer   Author: extremecoders-re   File: test_float.py    (license) View Source Project 6 votes vote down vote up
def test_roundtrip(self):
        def roundtrip(x):
            return fromHex(toHex(x))

        for x in [NAN, INF, self.MAX, self.MIN, self.MIN-self.TINY, self.TINY, 0.0]:
            self.identical(x, roundtrip(x))
            self.identical(-x, roundtrip(-x))

        # fromHex(toHex(x)) should exactly recover x, for any non-NaN float x.
        import random
        for i in xrange(10000):
            e = random.randrange(-1200, 1200)
            m = random.random()
            s = random.choice([1.0, -1.0])
            try:
                x = s*ldexp(m, e)
            except OverflowError:
                pass
            else:
                self.identical(x, fromHex(toHex(x))) 
Example 5
Project: python2-tracer   Author: extremecoders-re   File: test_random.py    (license) View Source Project 6 votes vote down vote up
def test_strong_reference_implementation(self):
        # Like test_referenceImplementation, but checks for exact bit-level
        # equality.  This should pass on any box where C double contains
        # at least 53 bits of precision (the underlying algorithm suffers
        # no rounding errors -- all results are exact).
        from math import ldexp

        expected = [0x0eab3258d2231fL,
                    0x1b89db315277a5L,
                    0x1db622a5518016L,
                    0x0b7f9af0d575bfL,
                    0x029e4c4db82240L,
                    0x04961892f5d673L,
                    0x02b291598e4589L,
                    0x11388382c15694L,
                    0x02dad977c9e1feL,
                    0x191d96d4d334c6L]
        self.gen.seed(61731L + (24903L<<32) + (614L<<64) + (42143L<<96))
        actual = self.randomlist(2000)[-10:]
        for a, e in zip(actual, expected):
            self.assertEqual(long(ldexp(a, 53)), e) 
Example 6
Project: web_ctp   Author: molebot   File: test_float.py    (license) View Source Project 6 votes vote down vote up
def test_roundtrip(self):
        def roundtrip(x):
            return fromHex(toHex(x))

        for x in [NAN, INF, self.MAX, self.MIN, self.MIN-self.TINY, self.TINY, 0.0]:
            self.identical(x, roundtrip(x))
            self.identical(-x, roundtrip(-x))

        # fromHex(toHex(x)) should exactly recover x, for any non-NaN float x.
        import random
        for i in range(10000):
            e = random.randrange(-1200, 1200)
            m = random.random()
            s = random.choice([1.0, -1.0])
            try:
                x = s*ldexp(m, e)
            except OverflowError:
                pass
            else:
                self.identical(x, fromHex(toHex(x))) 
Example 7
Project: web_ctp   Author: molebot   File: test_random.py    (license) View Source Project 6 votes vote down vote up
def test_strong_reference_implementation(self):
        # Like test_referenceImplementation, but checks for exact bit-level
        # equality.  This should pass on any box where C double contains
        # at least 53 bits of precision (the underlying algorithm suffers
        # no rounding errors -- all results are exact).
        from math import ldexp

        expected = [0x0eab3258d2231f,
                    0x1b89db315277a5,
                    0x1db622a5518016,
                    0x0b7f9af0d575bf,
                    0x029e4c4db82240,
                    0x04961892f5d673,
                    0x02b291598e4589,
                    0x11388382c15694,
                    0x02dad977c9e1fe,
                    0x191d96d4d334c6]
        self.gen.seed(61731 + (24903<<32) + (614<<64) + (42143<<96))
        actual = self.randomlist(2000)[-10:]
        for a, e in zip(actual, expected):
            self.assertEqual(int(ldexp(a, 53)), e) 
Example 8
Project: MacHeap   Author: blankwall   File: pfloat.py    (license) View Source Project 6 votes vote down vote up
def getf(self):
        """convert the stored floating-point number into a python native float"""
        exponentbias = (2**self.components[1])/2 - 1
        res = bitmap.new( self.__getvalue__(), sum(self.components) )

        # extract components
        res,sign = bitmap.shift(res, self.components[0])
        res,exponent = bitmap.shift(res, self.components[1])
        res,mantissa = bitmap.shift(res, self.components[2])

        if exponent > 0 and exponent < (2**self.components[2]-1):
            # convert to float
            s = -1 if sign else +1
            e = exponent - exponentbias
            m = 1.0 + (float(mantissa) / 2**self.components[2])

            # done
            return math.ldexp( math.copysign(m,s), e)

        # FIXME: this should return NaN or something
        Log.warn('float_t.getf : {:s} : Invalid exponent value : {:d}'.format(self.instance(), exponent))
        return 0.0 
Example 9
Project: pefile.pypy   Author: cloudtracer   File: test_float.py    (license) View Source Project 6 votes vote down vote up
def test_roundtrip(self):
        def roundtrip(x):
            return fromHex(toHex(x))

        for x in [NAN, INF, self.MAX, self.MIN, self.MIN-self.TINY, self.TINY, 0.0]:
            self.identical(x, roundtrip(x))
            self.identical(-x, roundtrip(-x))

        # fromHex(toHex(x)) should exactly recover x, for any non-NaN float x.
        import random
        for i in xrange(10000):
            e = random.randrange(-1200, 1200)
            m = random.random()
            s = random.choice([1.0, -1.0])
            try:
                x = s*ldexp(m, e)
            except OverflowError:
                pass
            else:
                self.identical(x, fromHex(toHex(x))) 
Example 10
Project: pefile.pypy   Author: cloudtracer   File: test_random.py    (license) View Source Project 6 votes vote down vote up
def test_strong_reference_implementation(self):
        # Like test_referenceImplementation, but checks for exact bit-level
        # equality.  This should pass on any box where C double contains
        # at least 53 bits of precision (the underlying algorithm suffers
        # no rounding errors -- all results are exact).
        from math import ldexp

        expected = [0x0eab3258d2231fL,
                    0x1b89db315277a5L,
                    0x1db622a5518016L,
                    0x0b7f9af0d575bfL,
                    0x029e4c4db82240L,
                    0x04961892f5d673L,
                    0x02b291598e4589L,
                    0x11388382c15694L,
                    0x02dad977c9e1feL,
                    0x191d96d4d334c6L]
        self.gen.seed(61731L + (24903L<<32) + (614L<<64) + (42143L<<96))
        actual = self.randomlist(2000)[-10:]
        for a, e in zip(actual, expected):
            self.assertEqual(long(ldexp(a, 53)), e) 
Example 11
Project: ouroboros   Author: pybee   File: cmath.py    (license) View Source Project 6 votes vote down vote up
def _log(z):
    abs_x = abs(z.real)
    abs_y = abs(z.imag)

    if abs_x > _LARGE_INT or abs_y > _LARGE_INT:
        return complex(math.log(math.hypot(abs_x/2, abs_y/2)) + _LOG_2,
                       math.atan2(z.imag, z.real))
    if abs_x < _DBL_MIN and abs_y < _DBL_MIN:
        if abs_x > 0 or abs_y > 0:
            return complex(math.log(math.hypot(math.ldexp(abs_x, _DBL_MANT_DIG),
                                    math.ldexp(abs_y, _DBL_MANT_DIG)))
                           - _DBL_MANT_DIG * _LOG_2,
                           math.atan2(z.imag, z.real))
        raise ValueError

    rad, phi = polar(z)
    return complex(math.log(rad), phi) 
Example 12
Project: ouroboros   Author: pybee   File: test_float.py    (license) View Source Project 6 votes vote down vote up
def test_roundtrip(self):
        def roundtrip(x):
            return fromHex(toHex(x))

        for x in [NAN, INF, self.MAX, self.MIN, self.MIN-self.TINY, self.TINY, 0.0]:
            self.identical(x, roundtrip(x))
            self.identical(-x, roundtrip(-x))

        # fromHex(toHex(x)) should exactly recover x, for any non-NaN float x.
        import random
        for i in range(10000):
            e = random.randrange(-1200, 1200)
            m = random.random()
            s = random.choice([1.0, -1.0])
            try:
                x = s*ldexp(m, e)
            except OverflowError:
                pass
            else:
                self.identical(x, fromHex(toHex(x))) 
Example 13
Project: ouroboros   Author: pybee   File: test_random.py    (license) View Source Project 6 votes vote down vote up
def test_strong_reference_implementation(self):
        # Like test_referenceImplementation, but checks for exact bit-level
        # equality.  This should pass on any box where C double contains
        # at least 53 bits of precision (the underlying algorithm suffers
        # no rounding errors -- all results are exact).
        from math import ldexp

        expected = [0x0eab3258d2231f,
                    0x1b89db315277a5,
                    0x1db622a5518016,
                    0x0b7f9af0d575bf,
                    0x029e4c4db82240,
                    0x04961892f5d673,
                    0x02b291598e4589,
                    0x11388382c15694,
                    0x02dad977c9e1fe,
                    0x191d96d4d334c6]
        self.gen.seed(61731 + (24903<<32) + (614<<64) + (42143<<96))
        actual = self.randomlist(2000)[-10:]
        for a, e in zip(actual, expected):
            self.assertEqual(int(ldexp(a, 53)), e) 
Example 14
Project: ndk-python   Author: gittor   File: test_float.py    (license) View Source Project 6 votes vote down vote up
def test_roundtrip(self):
        def roundtrip(x):
            return fromHex(toHex(x))

        for x in [NAN, INF, self.MAX, self.MIN, self.MIN-self.TINY, self.TINY, 0.0]:
            self.identical(x, roundtrip(x))
            self.identical(-x, roundtrip(-x))

        # fromHex(toHex(x)) should exactly recover x, for any non-NaN float x.
        import random
        for i in xrange(10000):
            e = random.randrange(-1200, 1200)
            m = random.random()
            s = random.choice([1.0, -1.0])
            try:
                x = s*ldexp(m, e)
            except OverflowError:
                pass
            else:
                self.identical(x, fromHex(toHex(x))) 
Example 15
Project: ndk-python   Author: gittor   File: test_random.py    (license) View Source Project 6 votes vote down vote up
def test_strong_reference_implementation(self):
        # Like test_referenceImplementation, but checks for exact bit-level
        # equality.  This should pass on any box where C double contains
        # at least 53 bits of precision (the underlying algorithm suffers
        # no rounding errors -- all results are exact).
        from math import ldexp

        expected = [0x0eab3258d2231fL,
                    0x1b89db315277a5L,
                    0x1db622a5518016L,
                    0x0b7f9af0d575bfL,
                    0x029e4c4db82240L,
                    0x04961892f5d673L,
                    0x02b291598e4589L,
                    0x11388382c15694L,
                    0x02dad977c9e1feL,
                    0x191d96d4d334c6L]
        self.gen.seed(61731L + (24903L<<32) + (614L<<64) + (42143L<<96))
        actual = self.randomlist(2000)[-10:]
        for a, e in zip(actual, expected):
            self.assertEqual(long(ldexp(a, 53)), e) 
Example 16
Project: kbe_server   Author: xiaohaoppy   File: test_float.py    (license) View Source Project 6 votes vote down vote up
def test_roundtrip(self):
        def roundtrip(x):
            return fromHex(toHex(x))

        for x in [NAN, INF, self.MAX, self.MIN, self.MIN-self.TINY, self.TINY, 0.0]:
            self.identical(x, roundtrip(x))
            self.identical(-x, roundtrip(-x))

        # fromHex(toHex(x)) should exactly recover x, for any non-NaN float x.
        import random
        for i in range(10000):
            e = random.randrange(-1200, 1200)
            m = random.random()
            s = random.choice([1.0, -1.0])
            try:
                x = s*ldexp(m, e)
            except OverflowError:
                pass
            else:
                self.identical(x, fromHex(toHex(x))) 
Example 17
Project: kbe_server   Author: xiaohaoppy   File: test_random.py    (license) View Source Project 6 votes vote down vote up
def test_strong_reference_implementation(self):
        # Like test_referenceImplementation, but checks for exact bit-level
        # equality.  This should pass on any box where C double contains
        # at least 53 bits of precision (the underlying algorithm suffers
        # no rounding errors -- all results are exact).
        from math import ldexp

        expected = [0x0eab3258d2231f,
                    0x1b89db315277a5,
                    0x1db622a5518016,
                    0x0b7f9af0d575bf,
                    0x029e4c4db82240,
                    0x04961892f5d673,
                    0x02b291598e4589,
                    0x11388382c15694,
                    0x02dad977c9e1fe,
                    0x191d96d4d334c6]
        self.gen.seed(61731 + (24903<<32) + (614<<64) + (42143<<96))
        actual = self.randomlist(2000)[-10:]
        for a, e in zip(actual, expected):
            self.assertEqual(int(ldexp(a, 53)), e) 
Example 18
Project: DimmiLitho   Author: vincentlv   File: record.py    (license) View Source Project 6 votes vote down vote up
def _int_to_real(num):
    """
    Convert REAL8 from internal integer representation to Python reals.

    Zeroes:
        >>> print(_int_to_real(0x0))
        0.0
        >>> print(_int_to_real(0x8000000000000000)) # negative
        0.0
        >>> print(_int_to_real(0xff00000000000000)) # denormalized
        0.0

    Others:
        >>> print(_int_to_real(0x4110000000000000))
        1.0
        >>> print(_int_to_real(0xC120000000000000))
        -2.0
    """
    sgn = -1 if 0x8000000000000000 & num else 1
    mant = num & 0x00ffffffffffffff
    exp = (num >> 56) & 0x7f
    return math.ldexp(sgn * mant, 4 * (exp - 64) - 56) 
Example 19
Project: kinect-2-libras   Author: inessadl   File: aifc.py    (Apache License 2.0) View Source Project 5 votes vote down vote up
def _write_float(f, x):
    import math
    if x < 0:
        sign = 0x8000
        x = x * -1
    else:
        sign = 0
    if x == 0:
        expon = 0
        himant = 0
        lomant = 0
    else:
        fmant, expon = math.frexp(x)
        if expon > 16384 or fmant >= 1:     # Infinity or NaN
            expon = sign|0x7FFF
            himant = 0
            lomant = 0
        else:                   # Finite
            expon = expon + 16382
            if expon < 0:           # denormalized
                fmant = math.ldexp(fmant, expon)
                expon = 0
            expon = expon | sign
            fmant = math.ldexp(fmant, 32)
            fsmant = math.floor(fmant)
            himant = long(fsmant)
            fmant = math.ldexp(fmant - fsmant, 32)
            fsmant = math.floor(fmant)
            lomant = long(fsmant)
    _write_short(f, expon)
    _write_long(f, himant)
    _write_long(f, lomant) 
Example 20
Project: s2sphere   Author: sidewalklabs   File: sphere.py    (license) View Source Project 5 votes vote down vote up
def get_value(self, level):
        """The value of this metric at a given level.

        :returns:
            Depending on whether this is used in one or two dimensions, this is
            an angle in radians or a solid angle in steradians.
        """
        return math.ldexp(self.deriv(), -self.__dim * level) 
Example 21
Project: hostapd-mana   Author: adde88   File: aifc.py    (license) View Source Project 5 votes vote down vote up
def _write_float(f, x):
    import math
    if x < 0:
        sign = 0x8000
        x = x * -1
    else:
        sign = 0
    if x == 0:
        expon = 0
        himant = 0
        lomant = 0
    else:
        fmant, expon = math.frexp(x)
        if expon > 16384 or fmant >= 1 or fmant != fmant: # Infinity or NaN
            expon = sign|0x7FFF
            himant = 0
            lomant = 0
        else:                   # Finite
            expon = expon + 16382
            if expon < 0:           # denormalized
                fmant = math.ldexp(fmant, expon)
                expon = 0
            expon = expon | sign
            fmant = math.ldexp(fmant, 32)
            fsmant = math.floor(fmant)
            himant = long(fsmant)
            fmant = math.ldexp(fmant - fsmant, 32)
            fsmant = math.floor(fmant)
            lomant = long(fsmant)
    _write_ushort(f, expon)
    _write_ulong(f, himant)
    _write_ulong(f, lomant) 
Example 22
Project: cuny-bdif   Author: aristotle-tek   File: utils.py    (license) View Source Project 5 votes vote down vote up
def minimum_part_size(size_in_bytes, default_part_size=DEFAULT_PART_SIZE):
    """Calculate the minimum part size needed for a multipart upload.

    Glacier allows a maximum of 10,000 parts per upload.  It also
    states that the maximum archive size is 10,000 * 4 GB, which means
    the part size can range from 1MB to 4GB (provided it is one 1MB
    multiplied by a power of 2).

    This function will compute what the minimum part size must be in
    order to upload a file of size ``size_in_bytes``.

    It will first check if ``default_part_size`` is sufficient for
    a part size given the ``size_in_bytes``.  If this is not the case,
    then the smallest part size than can accomodate a file of size
    ``size_in_bytes`` will be returned.

    If the file size is greater than the maximum allowed archive
    size of 10,000 * 4GB, a ``ValueError`` will be raised.

    """
    # The default part size (4 MB) will be too small for a very large
    # archive, as there is a limit of 10,000 parts in a multipart upload.
    # This puts the maximum allowed archive size with the default part size
    # at 40,000 MB. We need to do a sanity check on the part size, and find
    # one that works if the default is too small.
    part_size = _MEGABYTE
    if (default_part_size * MAXIMUM_NUMBER_OF_PARTS) < size_in_bytes:
        if size_in_bytes > (4096 * _MEGABYTE * 10000):
            raise ValueError("File size too large: %s" % size_in_bytes)
        min_part_size = size_in_bytes / 10000
        power = 3
        while part_size < min_part_size:
            part_size = math.ldexp(_MEGABYTE, power)
            power += 1
        part_size = int(part_size)
    else:
        part_size = default_part_size
    return part_size 
Example 23
Project: zippy   Author: securesystemslab   File: ctx_fp.py    (license) View Source Project 5 votes vote down vote up
def to_fixed(ctx, x, prec):
        return int(math.ldexp(x, prec)) 
Example 24
Project: zippy   Author: securesystemslab   File: libmpf.py    (license) View Source Project 5 votes vote down vote up
def to_float(s, strict=False):
    """
    Convert a raw mpf to a Python float. The result is exact if the
    bitcount of s is <= 53 and no underflow/overflow occurs.

    If the number is too large or too small to represent as a regular
    float, it will be converted to inf or 0.0. Setting strict=True
    forces an OverflowError to be raised instead.
    """
    sign, man, exp, bc = s
    if not man:
        if s == fzero: return 0.0
        if s == finf: return math_float_inf
        if s == fninf: return -math_float_inf
        return math_float_inf/math_float_inf
    if sign:
        man = -man
    try:
        if bc < 100:
            return math.ldexp(man, exp)
        # Try resizing the mantissa. Overflow may still happen here.
        n = bc - 53
        m = man >> n
        return math.ldexp(m, exp + n)
    except OverflowError:
        if strict:
            raise
        # Overflow to infinity
        if exp + bc > 0:
            if sign:
                return -math_float_inf
            else:
                return math_float_inf
        # Underflow to zero
        return 0.0 
Example 25
Project: zippy   Author: securesystemslab   File: test_float.py    (license) View Source Project 5 votes vote down vote up
def test_ends(self):
        self.identical(self.MIN, ldexp(1.0, -1022))
        self.identical(self.TINY, ldexp(1.0, -1074))
        self.identical(self.EPS, ldexp(1.0, -52))
        self.identical(self.MAX, 2.*(ldexp(1.0, 1023) - ldexp(1.0, 970))) 
Example 26
Project: zippy   Author: securesystemslab   File: test_long.py    (license) View Source Project 5 votes vote down vote up
def truediv(a, b):
    """Correctly-rounded true division for integers."""
    negative = a^b < 0
    a, b = abs(a), abs(b)

    # exceptions:  division by zero, overflow
    if not b:
        raise ZeroDivisionError("division by zero")
    if a >= DBL_MIN_OVERFLOW * b:
        raise OverflowError("int/int too large to represent as a float")

   # find integer d satisfying 2**(d - 1) <= a/b < 2**d
    d = a.bit_length() - b.bit_length()
    if d >= 0 and a >= 2**d * b or d < 0 and a * 2**-d >= b:
        d += 1

    # compute 2**-exp * a / b for suitable exp
    exp = max(d, DBL_MIN_EXP) - DBL_MANT_DIG
    a, b = a << max(-exp, 0), b << max(exp, 0)
    q, r = divmod(a, b)

    # round-half-to-even: fractional part is r/b, which is > 0.5 iff
    # 2*r > b, and == 0.5 iff 2*r == b.
    if 2*r > b or 2*r == b and q % 2 == 1:
        q += 1

    result = math.ldexp(q, exp)
    return -result if negative else result 
Example 27
Project: zippy   Author: securesystemslab   File: test_struct.py    (license) View Source Project 5 votes vote down vote up
def test_705836(self):
        # SF bug 705836.  "<f" and ">f" had a severe rounding bug, where a carry
        # from the low-order discarded bits could propagate into the exponent
        # field, causing the result to be wrong by a factor of 2.
        import math

        for base in range(1, 33):
            # smaller <- largest representable float less than base.
            delta = 0.5
            while base - delta / 2.0 != base:
                delta /= 2.0
            smaller = base - delta
            # Packing this rounds away a solid string of trailing 1 bits.
            packed = struct.pack("<f", smaller)
            unpacked = struct.unpack("<f", packed)[0]
            # This failed at base = 2, 4, and 32, with unpacked = 1, 2, and
            # 16, respectively.
            self.assertEqual(base, unpacked)
            bigpacked = struct.pack(">f", smaller)
            self.assertEqual(bigpacked, string_reverse(packed))
            unpacked = struct.unpack(">f", bigpacked)[0]
            self.assertEqual(base, unpacked)

        # Largest finite IEEE single.
        big = (1 << 24) - 1
        big = math.ldexp(big, 127 - 23)
        packed = struct.pack(">f", big)
        unpacked = struct.unpack(">f", packed)[0]
        self.assertEqual(big, unpacked)

        # The same, but tack on a 1 bit so it rounds up to infinity.
        big = (1 << 25) - 1
        big = math.ldexp(big, 127 - 24)
        self.assertRaises(OverflowError, struct.pack, ">f", big) 
Example 28
Project: zippy   Author: securesystemslab   File: test_math.py    (license) View Source Project 5 votes vote down vote up
def testLdexp(self):
        self.assertRaises(TypeError, math.ldexp)
        self.ftest('ldexp(0,1)', math.ldexp(0,1), 0)
        self.ftest('ldexp(1,1)', math.ldexp(1,1), 2)
        self.ftest('ldexp(1,-1)', math.ldexp(1,-1), 0.5)
        self.ftest('ldexp(-1,1)', math.ldexp(-1,1), -2)
        self.assertRaises(OverflowError, math.ldexp, 1., 1000000)
        self.assertRaises(OverflowError, math.ldexp, -1., 1000000)
        self.assertEqual(math.ldexp(1., -1000000), 0.)
        self.assertEqual(math.ldexp(-1., -1000000), -0.)
        self.assertEqual(math.ldexp(INF, 30), INF)
        self.assertEqual(math.ldexp(NINF, -213), NINF)
        self.assertTrue(math.isnan(math.ldexp(NAN, 0)))

        # large second argument
        for n in [10**5, 10**10, 10**20, 10**40]:
            self.assertEqual(math.ldexp(INF, -n), INF)
            self.assertEqual(math.ldexp(NINF, -n), NINF)
            self.assertEqual(math.ldexp(1., -n), 0.)
            self.assertEqual(math.ldexp(-1., -n), -0.)
            self.assertEqual(math.ldexp(0., -n), 0.)
            self.assertEqual(math.ldexp(-0., -n), -0.)
            self.assertTrue(math.isnan(math.ldexp(NAN, -n)))

            self.assertRaises(OverflowError, math.ldexp, 1., n)
            self.assertRaises(OverflowError, math.ldexp, -1., n)
            self.assertEqual(math.ldexp(0., n), 0.)
            self.assertEqual(math.ldexp(-0., n), -0.)
            self.assertEqual(math.ldexp(INF, n), INF)
            self.assertEqual(math.ldexp(NINF, n), NINF)
            self.assertTrue(math.isnan(math.ldexp(NAN, n))) 
Example 29
Project: zippy   Author: securesystemslab   File: aifc.py    (license) View Source Project 5 votes vote down vote up
def _write_float(f, x):
    import math
    if x < 0:
        sign = 0x8000
        x = x * -1
    else:
        sign = 0
    if x == 0:
        expon = 0
        himant = 0
        lomant = 0
    else:
        fmant, expon = math.frexp(x)
        if expon > 16384 or fmant >= 1 or fmant != fmant: # Infinity or NaN
            expon = sign|0x7FFF
            himant = 0
            lomant = 0
        else:                   # Finite
            expon = expon + 16382
            if expon < 0:           # denormalized
                fmant = math.ldexp(fmant, expon)
                expon = 0
            expon = expon | sign
            fmant = math.ldexp(fmant, 32)
            fsmant = math.floor(fmant)
            himant = int(fsmant)
            fmant = math.ldexp(fmant - fsmant, 32)
            fsmant = math.floor(fmant)
            lomant = int(fsmant)
    _write_ushort(f, expon)
    _write_ulong(f, himant)
    _write_ulong(f, lomant) 
Example 30
Project: twic_close_reading   Author: jarmoza   File: ctx_fp.py    (license) View Source Project 5 votes vote down vote up
def to_fixed(ctx, x, prec):
        return int(math.ldexp(x, prec)) 
Example 31
Project: twic_close_reading   Author: jarmoza   File: libmpf.py    (license) View Source Project 5 votes vote down vote up
def to_float(s, strict=False):
    """
    Convert a raw mpf to a Python float. The result is exact if the
    bitcount of s is <= 53 and no underflow/overflow occurs.

    If the number is too large or too small to represent as a regular
    float, it will be converted to inf or 0.0. Setting strict=True
    forces an OverflowError to be raised instead.
    """
    sign, man, exp, bc = s
    if not man:
        if s == fzero: return 0.0
        if s == finf: return math_float_inf
        if s == fninf: return -math_float_inf
        return math_float_inf/math_float_inf
    if sign:
        man = -man
    try:
        if bc < 100:
            return math.ldexp(man, exp)
        # Try resizing the mantissa. Overflow may still happen here.
        n = bc - 53
        m = man >> n
        return math.ldexp(m, exp + n)
    except OverflowError:
        if strict:
            raise
        # Overflow to infinity
        if exp + bc > 0:
            if sign:
                return -math_float_inf
            else:
                return math_float_inf
        # Underflow to zero
        return 0.0 
Example 32
Project: krpcScripts   Author: jwvanderbeck   File: ctx_fp.py    (license) View Source Project 5 votes vote down vote up
def to_fixed(ctx, x, prec):
        return int(math.ldexp(x, prec)) 
Example 33
Project: krpcScripts   Author: jwvanderbeck   File: libmpf.py    (license) View Source Project 5 votes vote down vote up
def to_float(s, strict=False):
    """
    Convert a raw mpf to a Python float. The result is exact if the
    bitcount of s is <= 53 and no underflow/overflow occurs.

    If the number is too large or too small to represent as a regular
    float, it will be converted to inf or 0.0. Setting strict=True
    forces an OverflowError to be raised instead.
    """
    sign, man, exp, bc = s
    if not man:
        if s == fzero: return 0.0
        if s == finf: return math_float_inf
        if s == fninf: return -math_float_inf
        return math_float_inf/math_float_inf
    if sign:
        man = -man
    try:
        if bc < 100:
            return math.ldexp(man, exp)
        # Try resizing the mantissa. Overflow may still happen here.
        n = bc - 53
        m = man >> n
        return math.ldexp(m, exp + n)
    except OverflowError:
        if strict:
            raise
        # Overflow to infinity
        if exp + bc > 0:
            if sign:
                return -math_float_inf
            else:
                return math_float_inf
        # Underflow to zero
        return 0.0 
Example 34
Project: oil   Author: oilshell   File: test_float.py    (license) View Source Project 5 votes vote down vote up
def test_ends(self):
        self.identical(self.MIN, ldexp(1.0, -1022))
        self.identical(self.TINY, ldexp(1.0, -1074))
        self.identical(self.EPS, ldexp(1.0, -52))
        self.identical(self.MAX, 2.*(ldexp(1.0, 1023) - ldexp(1.0, 970))) 
Example 35
Project: oil   Author: oilshell   File: test_long_future.py    (license) View Source Project 5 votes vote down vote up
def truediv(a, b):
    """Correctly-rounded true division for integers."""
    negative = a^b < 0
    a, b = abs(a), abs(b)

    # exceptions:  division by zero, overflow
    if not b:
        raise ZeroDivisionError("division by zero")
    if a >= DBL_MIN_OVERFLOW * b:
        raise OverflowError("int/int too large to represent as a float")

   # find integer d satisfying 2**(d - 1) <= a/b < 2**d
    d = a.bit_length() - b.bit_length()
    if d >= 0 and a >= 2**d * b or d < 0 and a * 2**-d >= b:
        d += 1

    # compute 2**-exp * a / b for suitable exp
    exp = max(d, DBL_MIN_EXP) - DBL_MANT_DIG
    a, b = a << max(-exp, 0), b << max(exp, 0)
    q, r = divmod(a, b)

    # round-half-to-even: fractional part is r/b, which is > 0.5 iff
    # 2*r > b, and == 0.5 iff 2*r == b.
    if 2*r > b or 2*r == b and q % 2 == 1:
        q += 1

    result = math.ldexp(float(q), exp)
    return -result if negative else result 
Example 36
Project: oil   Author: oilshell   File: test_struct.py    (license) View Source Project 5 votes vote down vote up
def test_705836(self):
        # SF bug 705836.  "<f" and ">f" had a severe rounding bug, where a carry
        # from the low-order discarded bits could propagate into the exponent
        # field, causing the result to be wrong by a factor of 2.
        import math

        for base in range(1, 33):
            # smaller <- largest representable float less than base.
            delta = 0.5
            while base - delta / 2.0 != base:
                delta /= 2.0
            smaller = base - delta
            # Packing this rounds away a solid string of trailing 1 bits.
            packed = struct.pack("<f", smaller)
            unpacked = struct.unpack("<f", packed)[0]
            # This failed at base = 2, 4, and 32, with unpacked = 1, 2, and
            # 16, respectively.
            self.assertEqual(base, unpacked)
            bigpacked = struct.pack(">f", smaller)
            self.assertEqual(bigpacked, string_reverse(packed))
            unpacked = struct.unpack(">f", bigpacked)[0]
            self.assertEqual(base, unpacked)

        # Largest finite IEEE single.
        big = (1 << 24) - 1
        big = math.ldexp(big, 127 - 23)
        packed = struct.pack(">f", big)
        unpacked = struct.unpack(">f", packed)[0]
        self.assertEqual(big, unpacked)

        # The same, but tack on a 1 bit so it rounds up to infinity.
        big = (1 << 25) - 1
        big = math.ldexp(big, 127 - 24)
        self.assertRaises(OverflowError, struct.pack, ">f", big) 
Example 37
Project: oil   Author: oilshell   File: aifc.py    (license) View Source Project 5 votes vote down vote up
def _write_float(f, x):
    import math
    if x < 0:
        sign = 0x8000
        x = x * -1
    else:
        sign = 0
    if x == 0:
        expon = 0
        himant = 0
        lomant = 0
    else:
        fmant, expon = math.frexp(x)
        if expon > 16384 or fmant >= 1 or fmant != fmant: # Infinity or NaN
            expon = sign|0x7FFF
            himant = 0
            lomant = 0
        else:                   # Finite
            expon = expon + 16382
            if expon < 0:           # denormalized
                fmant = math.ldexp(fmant, expon)
                expon = 0
            expon = expon | sign
            fmant = math.ldexp(fmant, 32)
            fsmant = math.floor(fmant)
            himant = long(fsmant)
            fmant = math.ldexp(fmant - fsmant, 32)
            fsmant = math.floor(fmant)
            lomant = long(fsmant)
    _write_ushort(f, expon)
    _write_ulong(f, himant)
    _write_ulong(f, lomant) 
Example 38
Project: python2-tracer   Author: extremecoders-re   File: test_float.py    (license) View Source Project 5 votes vote down vote up
def test_ends(self):
        self.identical(self.MIN, ldexp(1.0, -1022))
        self.identical(self.TINY, ldexp(1.0, -1074))
        self.identical(self.EPS, ldexp(1.0, -52))
        self.identical(self.MAX, 2.*(ldexp(1.0, 1023) - ldexp(1.0, 970))) 
Example 39
Project: python2-tracer   Author: extremecoders-re   File: test_long_future.py    (license) View Source Project 5 votes vote down vote up
def truediv(a, b):
    """Correctly-rounded true division for integers."""
    negative = a^b < 0
    a, b = abs(a), abs(b)

    # exceptions:  division by zero, overflow
    if not b:
        raise ZeroDivisionError("division by zero")
    if a >= DBL_MIN_OVERFLOW * b:
        raise OverflowError("int/int too large to represent as a float")

   # find integer d satisfying 2**(d - 1) <= a/b < 2**d
    d = a.bit_length() - b.bit_length()
    if d >= 0 and a >= 2**d * b or d < 0 and a * 2**-d >= b:
        d += 1

    # compute 2**-exp * a / b for suitable exp
    exp = max(d, DBL_MIN_EXP) - DBL_MANT_DIG
    a, b = a << max(-exp, 0), b << max(exp, 0)
    q, r = divmod(a, b)

    # round-half-to-even: fractional part is r/b, which is > 0.5 iff
    # 2*r > b, and == 0.5 iff 2*r == b.
    if 2*r > b or 2*r == b and q % 2 == 1:
        q += 1

    result = math.ldexp(float(q), exp)
    return -result if negative else result 
Example 40
Project: python2-tracer   Author: extremecoders-re   File: test_struct.py    (license) View Source Project 5 votes vote down vote up
def test_705836(self):
        # SF bug 705836.  "<f" and ">f" had a severe rounding bug, where a carry
        # from the low-order discarded bits could propagate into the exponent
        # field, causing the result to be wrong by a factor of 2.
        import math

        for base in range(1, 33):
            # smaller <- largest representable float less than base.
            delta = 0.5
            while base - delta / 2.0 != base:
                delta /= 2.0
            smaller = base - delta
            # Packing this rounds away a solid string of trailing 1 bits.
            packed = struct.pack("<f", smaller)
            unpacked = struct.unpack("<f", packed)[0]
            # This failed at base = 2, 4, and 32, with unpacked = 1, 2, and
            # 16, respectively.
            self.assertEqual(base, unpacked)
            bigpacked = struct.pack(">f", smaller)
            self.assertEqual(bigpacked, string_reverse(packed))
            unpacked = struct.unpack(">f", bigpacked)[0]
            self.assertEqual(base, unpacked)

        # Largest finite IEEE single.
        big = (1 << 24) - 1
        big = math.ldexp(big, 127 - 23)
        packed = struct.pack(">f", big)
        unpacked = struct.unpack(">f", packed)[0]
        self.assertEqual(big, unpacked)

        # The same, but tack on a 1 bit so it rounds up to infinity.
        big = (1 << 25) - 1
        big = math.ldexp(big, 127 - 24)
        self.assertRaises(OverflowError, struct.pack, ">f", big) 
Example 41
Project: python2-tracer   Author: extremecoders-re   File: aifc.py    (license) View Source Project 5 votes vote down vote up
def _write_float(f, x):
    import math
    if x < 0:
        sign = 0x8000
        x = x * -1
    else:
        sign = 0
    if x == 0:
        expon = 0
        himant = 0
        lomant = 0
    else:
        fmant, expon = math.frexp(x)
        if expon > 16384 or fmant >= 1 or fmant != fmant: # Infinity or NaN
            expon = sign|0x7FFF
            himant = 0
            lomant = 0
        else:                   # Finite
            expon = expon + 16382
            if expon < 0:           # denormalized
                fmant = math.ldexp(fmant, expon)
                expon = 0
            expon = expon | sign
            fmant = math.ldexp(fmant, 32)
            fsmant = math.floor(fmant)
            himant = long(fsmant)
            fmant = math.ldexp(fmant - fsmant, 32)
            fsmant = math.floor(fmant)
            lomant = long(fsmant)
    _write_ushort(f, expon)
    _write_ulong(f, himant)
    _write_ulong(f, lomant) 
Example 42
Project: sslstrip-hsts-openwrt   Author: adde88   File: aifc.py    (license) View Source Project 5 votes vote down vote up
def _write_float(f, x):
    import math
    if x < 0:
        sign = 0x8000
        x = x * -1
    else:
        sign = 0
    if x == 0:
        expon = 0
        himant = 0
        lomant = 0
    else:
        fmant, expon = math.frexp(x)
        if expon > 16384 or fmant >= 1 or fmant != fmant: # Infinity or NaN
            expon = sign|0x7FFF
            himant = 0
            lomant = 0
        else:                   # Finite
            expon = expon + 16382
            if expon < 0:           # denormalized
                fmant = math.ldexp(fmant, expon)
                expon = 0
            expon = expon | sign
            fmant = math.ldexp(fmant, 32)
            fsmant = math.floor(fmant)
            himant = long(fsmant)
            fmant = math.ldexp(fmant - fsmant, 32)
            fsmant = math.floor(fmant)
            lomant = long(fsmant)
    _write_ushort(f, expon)
    _write_ulong(f, himant)
    _write_ulong(f, lomant) 
Example 43
Project: web_ctp   Author: molebot   File: test_float.py    (license) View Source Project 5 votes vote down vote up
def test_ends(self):
        self.identical(self.MIN, ldexp(1.0, -1022))
        self.identical(self.TINY, ldexp(1.0, -1074))
        self.identical(self.EPS, ldexp(1.0, -52))
        self.identical(self.MAX, 2.*(ldexp(1.0, 1023) - ldexp(1.0, 970))) 
Example 44
Project: web_ctp   Author: molebot   File: test_long.py    (license) View Source Project 5 votes vote down vote up
def truediv(a, b):
    """Correctly-rounded true division for integers."""
    negative = a^b < 0
    a, b = abs(a), abs(b)

    # exceptions:  division by zero, overflow
    if not b:
        raise ZeroDivisionError("division by zero")
    if a >= DBL_MIN_OVERFLOW * b:
        raise OverflowError("int/int too large to represent as a float")

   # find integer d satisfying 2**(d - 1) <= a/b < 2**d
    d = a.bit_length() - b.bit_length()
    if d >= 0 and a >= 2**d * b or d < 0 and a * 2**-d >= b:
        d += 1

    # compute 2**-exp * a / b for suitable exp
    exp = max(d, DBL_MIN_EXP) - DBL_MANT_DIG
    a, b = a << max(-exp, 0), b << max(exp, 0)
    q, r = divmod(a, b)

    # round-half-to-even: fractional part is r/b, which is > 0.5 iff
    # 2*r > b, and == 0.5 iff 2*r == b.
    if 2*r > b or 2*r == b and q % 2 == 1:
        q += 1

    result = math.ldexp(q, exp)
    return -result if negative else result 
Example 45
Project: web_ctp   Author: molebot   File: test_math.py    (license) View Source Project 5 votes vote down vote up
def testLdexp(self):
        self.assertRaises(TypeError, math.ldexp)
        self.ftest('ldexp(0,1)', math.ldexp(0,1), 0)
        self.ftest('ldexp(1,1)', math.ldexp(1,1), 2)
        self.ftest('ldexp(1,-1)', math.ldexp(1,-1), 0.5)
        self.ftest('ldexp(-1,1)', math.ldexp(-1,1), -2)
        self.assertRaises(OverflowError, math.ldexp, 1., 1000000)
        self.assertRaises(OverflowError, math.ldexp, -1., 1000000)
        self.assertEqual(math.ldexp(1., -1000000), 0.)
        self.assertEqual(math.ldexp(-1., -1000000), -0.)
        self.assertEqual(math.ldexp(INF, 30), INF)
        self.assertEqual(math.ldexp(NINF, -213), NINF)
        self.assertTrue(math.isnan(math.ldexp(NAN, 0)))

        # large second argument
        for n in [10**5, 10**10, 10**20, 10**40]:
            self.assertEqual(math.ldexp(INF, -n), INF)
            self.assertEqual(math.ldexp(NINF, -n), NINF)
            self.assertEqual(math.ldexp(1., -n), 0.)
            self.assertEqual(math.ldexp(-1., -n), -0.)
            self.assertEqual(math.ldexp(0., -n), 0.)
            self.assertEqual(math.ldexp(-0., -n), -0.)
            self.assertTrue(math.isnan(math.ldexp(NAN, -n)))

            self.assertRaises(OverflowError, math.ldexp, 1., n)
            self.assertRaises(OverflowError, math.ldexp, -1., n)
            self.assertEqual(math.ldexp(0., n), 0.)
            self.assertEqual(math.ldexp(-0., n), -0.)
            self.assertEqual(math.ldexp(INF, n), INF)
            self.assertEqual(math.ldexp(NINF, n), NINF)
            self.assertTrue(math.isnan(math.ldexp(NAN, n))) 
Example 46
Project: web_ctp   Author: molebot   File: test_math.py    (license) View Source Project 5 votes vote down vote up
def testLog2Exact(self):
        #fixme brython.   
        # Check that we get exact equality for log2 of powers of 2.
        actual = [math.log2(math.ldexp(1.0, n)) for n in range(-1074, 1024)]
        expected = [float(n) for n in range(-1074, 1024)]
        self.assertEqual(actual, expected) 
Example 47
Project: web_ctp   Author: molebot   File: _struct.py    (license) View Source Project 5 votes vote down vote up
def float_unpack(Q, size, le):
    """Convert a 32-bit or 64-bit integer created
    by float_pack into a Python float."""

    if size == 8:
        MIN_EXP = -1021  # = sys.float_info.min_exp
        MAX_EXP = 1024   # = sys.float_info.max_exp
        MANT_DIG = 53    # = sys.float_info.mant_dig
        BITS = 64
    elif size == 4:
        MIN_EXP = -125   # C's FLT_MIN_EXP
        MAX_EXP = 128    # FLT_MAX_EXP
        MANT_DIG = 24    # FLT_MANT_DIG
        BITS = 32
    else:
        raise ValueError("invalid size value")

    if Q >> BITS:
         raise ValueError("input out of range")

    # extract pieces
    sign = Q >> BITS - 1
    exp = (Q & ((1 << BITS - 1) - (1 << MANT_DIG - 1))) >> MANT_DIG - 1
    mant = Q & ((1 << MANT_DIG - 1) - 1)

    if exp == MAX_EXP - MIN_EXP + 2:
        # nan or infinity
        result = float('nan') if mant else float('inf')
    elif exp == 0:
        # subnormal or zero
        result = math.ldexp(float(mant), MIN_EXP - MANT_DIG)
    else:
        # normal
        mant += 1 << MANT_DIG - 1
        result = math.ldexp(float(mant), exp + MIN_EXP - MANT_DIG - 1)
    return -result if sign else result 
Example 48
Project: learneveryword   Author: karan   File: utils.py    (license) View Source Project 5 votes vote down vote up
def minimum_part_size(size_in_bytes, default_part_size=DEFAULT_PART_SIZE):
    """Calculate the minimum part size needed for a multipart upload.

    Glacier allows a maximum of 10,000 parts per upload.  It also
    states that the maximum archive size is 10,000 * 4 GB, which means
    the part size can range from 1MB to 4GB (provided it is one 1MB
    multiplied by a power of 2).

    This function will compute what the minimum part size must be in
    order to upload a file of size ``size_in_bytes``.

    It will first check if ``default_part_size`` is sufficient for
    a part size given the ``size_in_bytes``.  If this is not the case,
    then the smallest part size than can accomodate a file of size
    ``size_in_bytes`` will be returned.

    If the file size is greater than the maximum allowed archive
    size of 10,000 * 4GB, a ``ValueError`` will be raised.

    """
    # The default part size (4 MB) will be too small for a very large
    # archive, as there is a limit of 10,000 parts in a multipart upload.
    # This puts the maximum allowed archive size with the default part size
    # at 40,000 MB. We need to do a sanity check on the part size, and find
    # one that works if the default is too small.
    part_size = _MEGABYTE
    if (default_part_size * MAXIMUM_NUMBER_OF_PARTS) < size_in_bytes:
        if size_in_bytes > (4096 * _MEGABYTE * 10000):
            raise ValueError("File size too large: %s" % size_in_bytes)
        min_part_size = size_in_bytes / 10000
        power = 3
        while part_size < min_part_size:
            part_size = math.ldexp(_MEGABYTE, power)
            power += 1
        part_size = int(part_size)
    else:
        part_size = default_part_size
    return part_size 
Example 49
Project: hyper-engine   Author: maxim5   File: sugar.py    (license) View Source Project 5 votes vote down vote up
def ldexp(node, i): return merge([node], lambda x: math.ldexp(x, i)) 
Example 50
Project: pefile.pypy   Author: cloudtracer   File: test_float.py    (license) View Source Project 5 votes vote down vote up
def test_ends(self):
        self.identical(self.MIN, ldexp(1.0, -1022))
        self.identical(self.TINY, ldexp(1.0, -1074))
        self.identical(self.EPS, ldexp(1.0, -52))
        self.identical(self.MAX, 2.*(ldexp(1.0, 1023) - ldexp(1.0, 970)))