Python numpy.ldexp函数代码示例

 def test_ldexp_invalid(self):
     with pytest.raises(TypeError) as exc:
         np.ldexp(3. * u.m, 4.)
     # built-in TypeError, so can't check content of exception
     with pytest.raises(TypeError) as exc:
         np.ldexp(3., 4 * u.m)
     assert "Cannot use ldexp" in exc.value.args[0]

def _expm_product_helper(A, mu, iteration_stash, t, B):
    # Estimate expm(t*M).dot(B).
    # A = M - mu*I
    # mu = mean(trace(M))
    # The iteration stash helps to compute numbers of iterations to use.
    # t is a scaling factor.
    # B is the input matrix for the linear operator.

    # Compute some input-dependent constants.
    tol = np.ldexp(1, -53)
    n0 = B.shape[1]
    m, s = iteration_stash.fragment_3_1(n0, t)

    #print('1-norm:', A.one_norm(), 't:', t, 'mu:', mu, 'n0:', n0, 'm:', m, 's:', s)

    # Get the lapack function for computing matrix norms.
    lange, = get_lapack_funcs(('lange',), (B,))

    F = B
    eta = np.exp(t*mu / float(s))
    for i in range(s):
        c1 = lange('i', B)
        for j in range(m):
            coeff = t / float(s*(j+1))
            B = coeff * A.dot(B)
            c2 = lange('i', B)
            F = F + B
            if c1 + c2 <= tol * lange('i', F):
                break
            c1 = c2
        F = eta * F
        B = F
    return F

    def __init__(self,
            Q_primary, primary_distn, primary_to_part,
            rate_on, rate_off):
        """

        """
        # Store the inputs.
        self.Q_primary = Q_primary
        self.primary_distn = primary_distn
        self.primary_to_part = primary_to_part
        self.rate_on = rate_on
        self.rate_off = rate_off

        # Precompute some summaries which can be computed quickly
        # and do not use much memory.
        # Summaries that are slow or complicated to compute or which may use
        # too much memory are computed on demand
        # through an explicit function call.
        self.nprimary = len(primary_to_part)
        self.nparts = len(set(primary_to_part.values()))
        self.ncompound = int(np.ldexp(self.nprimary, self.nparts))
        self.tolerance_distn = get_tolerance_distn(rate_off, rate_on)

        # Mark some attributes as un-initialized.
        # These attributes are related to the compound distribution,
        # and may be initialized later using init_compound().
        self.Q_compound = None
        self.compound_distn = None
        self.compound_to_primary = None
        self.compound_to_tolerances = None

    def test_half_ufuncs(self):
        """Test the various ufuncs"""

        a = np.array([0, 1, 2, 4, 2], dtype=float16)
        b = np.array([-2, 5, 1, 4, 3], dtype=float16)
        c = np.array([0, -1, -np.inf, np.nan, 6], dtype=float16)

        assert_equal(np.add(a, b), [-2, 6, 3, 8, 5])
        assert_equal(np.subtract(a, b), [2, -4, 1, 0, -1])
        assert_equal(np.multiply(a, b), [0, 5, 2, 16, 6])
        assert_equal(np.divide(a, b), [0, 0.199951171875, 2, 1, 0.66650390625])

        assert_equal(np.equal(a, b), [False, False, False, True, False])
        assert_equal(np.not_equal(a, b), [True, True, True, False, True])
        assert_equal(np.less(a, b), [False, True, False, False, True])
        assert_equal(np.less_equal(a, b), [False, True, False, True, True])
        assert_equal(np.greater(a, b), [True, False, True, False, False])
        assert_equal(np.greater_equal(a, b), [True, False, True, True, False])
        assert_equal(np.logical_and(a, b), [False, True, True, True, True])
        assert_equal(np.logical_or(a, b), [True, True, True, True, True])
        assert_equal(np.logical_xor(a, b), [True, False, False, False, False])
        assert_equal(np.logical_not(a), [True, False, False, False, False])

        assert_equal(np.isnan(c), [False, False, False, True, False])
        assert_equal(np.isinf(c), [False, False, True, False, False])
        assert_equal(np.isfinite(c), [True, True, False, False, True])
        assert_equal(np.signbit(b), [True, False, False, False, False])

        assert_equal(np.copysign(b, a), [2, 5, 1, 4, 3])

        assert_equal(np.maximum(a, b), [0, 5, 2, 4, 3])
        x = np.maximum(b, c)
        assert_(np.isnan(x[3]))
        x[3] = 0
        assert_equal(x, [0, 5, 1, 0, 6])
        assert_equal(np.minimum(a, b), [-2, 1, 1, 4, 2])
        x = np.minimum(b, c)
        assert_(np.isnan(x[3]))
        x[3] = 0
        assert_equal(x, [-2, -1, -np.inf, 0, 3])
        assert_equal(np.fmax(a, b), [0, 5, 2, 4, 3])
        assert_equal(np.fmax(b, c), [0, 5, 1, 4, 6])
        assert_equal(np.fmin(a, b), [-2, 1, 1, 4, 2])
        assert_equal(np.fmin(b, c), [-2, -1, -np.inf, 4, 3])

        assert_equal(np.floor_divide(a, b), [0, 0, 2, 1, 0])
        assert_equal(np.remainder(a, b), [0, 1, 0, 0, 2])
        assert_equal(np.divmod(a, b), ([0, 0, 2, 1, 0], [0, 1, 0, 0, 2]))
        assert_equal(np.square(b), [4, 25, 1, 16, 9])
        assert_equal(np.reciprocal(b), [-0.5, 0.199951171875, 1, 0.25, 0.333251953125])
        assert_equal(np.ones_like(b), [1, 1, 1, 1, 1])
        assert_equal(np.conjugate(b), b)
        assert_equal(np.absolute(b), [2, 5, 1, 4, 3])
        assert_equal(np.negative(b), [2, -5, -1, -4, -3])
        assert_equal(np.positive(b), b)
        assert_equal(np.sign(b), [-1, 1, 1, 1, 1])
        assert_equal(np.modf(b), ([0, 0, 0, 0, 0], b))
        assert_equal(np.frexp(b), ([-0.5, 0.625, 0.5, 0.5, 0.75], [2, 3, 1, 3, 2]))
        assert_equal(np.ldexp(b, [0, 1, 2, 4, 2]), [-2, 10, 4, 64, 12])

def nextfloat(fin):
    """Return (approximately) next float value (for f>0)."""
    d = 2**-52
    split = N.frexp(fin)
    while True:
        fout = N.ldexp(split[0] + d, split[1])
        if fin != fout:
            return fout
        d *= 2

    def decode(self, i):
        i = np.array(i)
        i = 255 - i
        sgn = i > 127
        e = np.array(np.floor(i / 16.0) - 8 * sgn + 1, dtype=np.uint8)
        f = i % 16
        data = np.ldexp(f, e + 2)
        e = MuLaw.etab[e-1]
        data = MuLaw.iscale * (1 - 2 * sgn) * (e + data)
	
        return data

    def test_roundtrip(self, ftype, frac_vals, exp_vals):
        for frac, exp in zip(frac_vals, exp_vals):
            f = np.ldexp(frac, exp, dtype=ftype)
            n, d = f.as_integer_ratio()

            try:
                # workaround for gh-9968
                nf = np.longdouble(str(n))
                df = np.longdouble(str(d))
            except (OverflowError, RuntimeWarning):
                # the values may not fit in any float type
                pytest.skip("longdouble too small on this platform")

            assert_equal(nf / df, f, "{}/{}".format(n, d))

def from_npfloat(x, prec=113, rnd=round_fast):
    """Create a raw mpf from a numpy float, rounding if necessary.
    If prec >= 113, the result is guaranteed to represent exactly the
    same number as the input. If prec is not specified, use prec=113."""
    y = float(x)
    if x == y: # ldexp overflows for float16
        return from_float(y, prec, rnd)
    import numpy as np
    if np.isfinite(x):
        m, e = np.frexp(x)
        return from_man_exp(int(np.ldexp(m, 113)), int(e-113), prec, rnd)
    if np.isposinf(x): return finf
    if np.isneginf(x): return fninf
    return fnan

def tiny_perturbation(arr):
	fr = numpy.frexp(arr)
	perturb = numpy.random.random(fr[0].shape) * 1e-12
	return numpy.ldexp(fr[0]+perturb, fr[1])

    def test_ldexp_invalid(self):
        with pytest.raises(TypeError):
            np.ldexp(3. * u.m, 4.)

        with pytest.raises(TypeError):
            np.ldexp(3., u.Quantity(4, u.m, dtype=int))

 def test_ldexp_array(self):
     assert np.all(np.ldexp(np.array([1., 2., 3.]) * u.m, [3, 2, 1])
                   == np.array([8., 8., 6.]) * u.m)

 def test_ldexp_scalar(self):
     assert np.ldexp(4. * u.m, 2) == 16. * u.m

def ldexp_usecase(x, y, result):
    np.ldexp(x, y, result)

def n_ldexp(a, b):
    """safe ldexp"""
    return np.ldexp(a, intify(b))

def math():
    global a, b, c, z, r

    print '###########################'
    print '#'
    print '#   数学相关'
    print '#'
    print '###########################'
    ###     三角函数    ###
    print '三角形斜边：\n', np.hypot(3*np.ones((3, 3)), 4*np.ones((3, 3)))
    print '弧度转角度1：\n', np.degrees(np.arange(12.)*np.pi/6)
    print '弧度转角度2：\n', np.rad2deg(np.pi/2)
    print '角度转弧度1：\n', np.radians(np.arange(12.)*30)
    print '角度转弧度2：\n', np.deg2rad(180)
    print '最大距离截断：\n', np.unwrap(np.linspace(0, np.pi, num=5))

    ###     取整    ###
    print '根据位数取整：\n', np.around([0.37, 1.64], decimals=1)
    print '四舍五入取整：\n', np.rint([0.37, 1.64])
    print '向零取整1：\n', np.fix([-1.5, -0.8, 0.37, 1.64])
    print '向零取整2：\n', np.trunc([-1.5, -0.8, 0.37, 1.64])
    print '向下取整：\n', np.floor([0.37, 1.64])
    print '向上取整：\n', np.ceil([0.37, 1.64])

    ###     四则运算    ###
    print '乘积：\n', np.prod([[1.,2.],[3.,4.]], axis=1)
    print '求和：\n', np.sum([[0, 1], [0, 5]], axis=0)
    print '累计乘积：\n', np.cumprod([[1, 2], [3, 4]])
    print '累计求和：\n', np.cumsum([[1, 2], [3, 4]])
    print '求差：\n', np.diff([[1, 2], [3, 4]])
    print '一维求差：\n', np.ediff1d([[1, 2], [3, 4]])
    print '梯度：\n', np.gradient(np.array([[1, 2, 6], [3, 4, 5]], dtype=np.float))
    print '向量积（叉积）：\n', np.cross([1, 2, 3], [4, 5, 6])
    print '加法：\n', np.add(np.arange(9).reshape(3, 3), np.arange(3))
    print '倒数：\n', np.reciprocal([1, 2., 3.33])
    print '负数：\n', np.negative([1.,-1.])
    print '乘法：\n', np.multiply(2.0, 4.0)
    print '除法：\n', np.divide(5.0, 4.0)
    print '除法带小数：\n', np.true_divide(5.0, 4.0)
    print '除法向下取整：\n', np.floor_divide(5.0, 4.0)
    print '指数：\n', np.power(np.arange(6), 3)
    print '减法：\n', np.subtract(1.0, 4.0)
    print '求余1：\n', np.mod([-3, -2, -1, 1, 2, 3], 2)
    print '求余2：\n', np.fmod([-3, -2, -1, 1, 2, 3], 2)
    print '求余3：\n', np.remainder([-3, -2, -1, 1, 2, 3], 2)
    print '小数+整数：\n', np.modf([0, 3.5])

    ###     正负符号    ###
    print '负数返回True：\n', np.signbit(np.array([1, -2.3, 2.1]))
    # 小于0返回-1, 等于0返回0, 大于0返回1
    print '正负符号：\n', np.sign([-5., 0, 4.5])
    # 将x2的符号应用到x1上。
    print '符号拷贝：\n', np.copysign([-1, 0, 1], -1.1)
    # 分解公式：y = x1 * 2**x2
    x1, x2 = np.frexp(np.arange(9))
    print '指数分解：\n', x1, x2
    # 构建公式：y = x1 * 2**x2，是分解公式的逆向操作
    print '指数构建：\n', np.ldexp(x1, x2)

    ###     复数    ###
    print '复数转角度：\n', np.angle([1.0, 1.0j, 1+1j])
    print '返回实数部分：\n', np.real(np.array([1+2j, 3+4j, 5+6j]))
    print '返回实数部分（虚数接近0）：\n', np.real_if_close([2.1 + 4e-14j], tol=1000)
    print '返回虚数部分：\n', np.imag(np.array([1+2j, 3+4j, 5+6j]))
    print '返回复数共轭矩阵：\n', np.conj(np.eye(2) + 1j * np.eye(2))

    ###     杂项    ###
    print '卷积：\n', np.convolve([1, 2, 3], [0, 1, 0.5])
    # 根据指定的区间，小于区间最小值的赋值为最小值，大于区间最大值的赋值为最大值
    print '截断：\n', np.clip(np.arange(10), 3, 6)
    print '平方根：\n', np.sqrt([4, -1, -3+4J])
    print '平方：\n', np.square([-1j, 1])
    print '绝对值（含复数）：\n', np.absolute([-1, -2])
    print '绝对值2：\n', np.fabs([-1, -2])
    print '最大值（含nan）：\n', np.maximum([2, 3, np.nan], [1, 5, 2])
    print '最小值（含nan）：\n', np.minimum([2, 3, np.nan], [1, 5, 2])
    print '最大值（忽略nan）：\n', np.fmax([2, 3, np.nan], [1, 5, 2])
    print '最小值（忽略nan）：\n', np.fmin([2, 3, np.nan], [1, 5, 2])
    # 在由xp和fp组成的坐标点中插值
    print '线性插值：\n', np.interp([0, 1, 1.5, 2.72, 3.14], xp=[1, 2, 3], fp=[3, 2, 0])