Python math.ldexp() Examples

The following are 30 code examples of math.ldexp(). 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 also want to check out all available functions/classes of the module math , or try the search function .
Example #1
Source Project: ironpython2   Author: IronLanguages   File: test_float.py    License: Apache License 2.0 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 #2
Source Project: ironpython2   Author: IronLanguages   File: test_random.py    License: Apache License 2.0 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 #3
Source Project: BinderFilter   Author: dxwu   File: test_float.py    License: MIT License 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 #4
Source Project: BinderFilter   Author: dxwu   File: test_random.py    License: MIT License 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 #5
Source Project: oss-ftp   Author: aliyun   File: test_float.py    License: MIT License 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 #6
Source Project: oss-ftp   Author: aliyun   File: test_random.py    License: MIT License 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 #7
Source Project: Fluid-Designer   Author: Microvellum   File: test_float.py    License: GNU General Public License v3.0 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 #8
Source Project: Fluid-Designer   Author: Microvellum   File: test_random.py    License: GNU General Public License v3.0 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 #9
Source Project: ironpython3   Author: IronLanguages   File: test_float.py    License: Apache License 2.0 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 #10
Source Project: ironpython3   Author: IronLanguages   File: test_random.py    License: Apache License 2.0 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 #11
Source Project: MARA_Framework   Author: xtiankisutsa   File: disassembly.py    License: GNU Lesser General Public License v3.0 6 votes vote down vote up
def _float_or_double(self, x, nmbits, nebits, suffix, nanfmt):
        nbits = nmbits + nebits + 1
        assert nbits % 32 == 0

        sbit, ebits, mbits = x >> (nbits - 1), (x >> nmbits) % (1 << nebits), x % (1 << nmbits)
        if ebits == (1 << nebits) - 1:
            result = 'NaN' if mbits else 'Infinity'
            if self.roundtrip and mbits:
                result += nanfmt.format(x)
        elif ebits == 0 and mbits == 0:
            result = '0.0'
        else:
            ebias = (1 << (nebits - 1)) - 1
            exponent = ebits - ebias - nmbits
            mantissa = mbits
            if ebits > 0:
                mantissa += 1 << nmbits
            else:
                exponent += 1

            if self.roundtrip:
                result = '0x{:X}p{}'.format(mantissa, exponent)
            else:
                result = repr(math.ldexp(mantissa, exponent))
        return '+-'[sbit] + result + suffix 
Example #12
Source Project: gcblue   Author: gcblue   File: test_float.py    License: BSD 3-Clause "New" or "Revised" License 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 #13
Source Project: MayaManipulatorDrawer   Author: yamahigashi   File: sceneRenderOverride.py    License: MIT License 6 votes vote down vote up
def _zoomRatio(self, basePoint):
        # type: (om.MPoint) -> float
        """Calculate zoom factor as distance from the current view's camera position."""
        # FIXME: all views share this value from current one.

        # camera distance
        cameraPath = omui.M3dView.active3dView().getCamera()
        camNode = om.MFnDependencyNode(cameraPath.node())
        isOrtho = camNode.findPlug("orthographic", False)

        camMat = cameraPath.inclusiveMatrix().homogenize()
        camPos = om.MPoint(
            camMat.getElement(3, 0),
            camMat.getElement(3, 1),
            camMat.getElement(3, 2),
        )

        if isOrtho.asBool():
            orthoWidth = camNode.findPlug("orthographicWidth", False).asFloat()
            return math.ldexp(orthoWidth, 3) * 0.01
        else:
            return basePoint.distanceTo(camPos) * 0.1 
Example #14
Source Project: Project-New-Reign---Nemesis-Main   Author: ShikyoKira   File: test_float.py    License: GNU General Public License v3.0 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 #15
Source Project: Project-New-Reign---Nemesis-Main   Author: ShikyoKira   File: test_random.py    License: GNU General Public License v3.0 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 #16
Source Project: medicare-demo   Author: ofermend   File: test_random.py    License: Apache License 2.0 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 #17
Source Project: CTFCrackTools-V2   Author: Acmesec   File: test_float.py    License: GNU General Public License v3.0 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 #18
Source Project: CTFCrackTools-V2   Author: Acmesec   File: test_random.py    License: GNU General Public License v3.0 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 #19
Source Project: jawfish   Author: war-and-code   File: _struct.py    License: MIT License 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 #20
Source Project: sphere   Author: qedus   File: sphere.py    License: MIT License 5 votes vote down vote up
def get_value(self, level):
        return math.ldexp(self.deriv(), -self.__dim * level) 
Example #21
Source Project: meddle   Author: glmcdona   File: aifc.py    License: MIT License 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 #22
Source Project: ironpython2   Author: IronLanguages   File: aifc.py    License: Apache License 2.0 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 #23
Source Project: ironpython2   Author: IronLanguages   File: test_long_future.py    License: Apache License 2.0 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 #24
Source Project: ironpython2   Author: IronLanguages   File: test_float.py    License: Apache License 2.0 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 #25
Source Project: ironpython2   Author: IronLanguages   File: test_math.py    License: Apache License 2.0 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, 10L**5, 10**10, 10L**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 #26
Source Project: BinderFilter   Author: dxwu   File: aifc.py    License: MIT License 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 #27
Source Project: BinderFilter   Author: dxwu   File: test_long_future.py    License: MIT License 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 #28
Source Project: BinderFilter   Author: dxwu   File: test_float.py    License: MIT License 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 #29
Source Project: BinderFilter   Author: dxwu   File: test_math.py    License: MIT License 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, 10L**5, 10**10, 10L**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 #30
Source Project: oss-ftp   Author: aliyun   File: aifc.py    License: MIT License 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)