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libmpi.py

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+"""
+Computational functions for interval arithmetic.
+
+"""
+
+from .backend import xrange
+
+from .libmpf import (
+    ComplexResult,
+    round_down, round_up, round_floor, round_ceiling, round_nearest,
+    prec_to_dps, repr_dps, dps_to_prec,
+    bitcount,
+    from_float,
+    fnan, finf, fninf, fzero, fhalf, fone, fnone,
+    mpf_sign, mpf_lt, mpf_le, mpf_gt, mpf_ge, mpf_eq, mpf_cmp,
+    mpf_min_max,
+    mpf_floor, from_int, to_int, to_str, from_str,
+    mpf_abs, mpf_neg, mpf_pos, mpf_add, mpf_sub, mpf_mul, mpf_mul_int,
+    mpf_div, mpf_shift, mpf_pow_int,
+    from_man_exp, MPZ_ONE)
+
+from .libelefun import (
+    mpf_log, mpf_exp, mpf_sqrt, mpf_atan, mpf_atan2,
+    mpf_pi, mod_pi2, mpf_cos_sin
+)
+
+from .gammazeta import mpf_gamma, mpf_rgamma, mpf_loggamma, mpc_loggamma
+
+def mpi_str(s, prec):
+    sa, sb = s
+    dps = prec_to_dps(prec) + 5
+    return "[%s, %s]" % (to_str(sa, dps), to_str(sb, dps))
+    #dps = prec_to_dps(prec)
+    #m = mpi_mid(s, prec)
+    #d = mpf_shift(mpi_delta(s, 20), -1)
+    #return "%s +/- %s" % (to_str(m, dps), to_str(d, 3))
+
+mpi_zero = (fzero, fzero)
+mpi_one = (fone, fone)
+
+def mpi_eq(s, t):
+    return s == t
+
+def mpi_ne(s, t):
+    return s != t
+
+def mpi_lt(s, t):
+    sa, sb = s
+    ta, tb = t
+    if mpf_lt(sb, ta): return True
+    if mpf_ge(sa, tb): return False
+    return None
+
+def mpi_le(s, t):
+    sa, sb = s
+    ta, tb = t
+    if mpf_le(sb, ta): return True
+    if mpf_gt(sa, tb): return False
+    return None
+
+def mpi_gt(s, t): return mpi_lt(t, s)
+def mpi_ge(s, t): return mpi_le(t, s)
+
+def mpi_add(s, t, prec=0):
+    sa, sb = s
+    ta, tb = t
+    a = mpf_add(sa, ta, prec, round_floor)
+    b = mpf_add(sb, tb, prec, round_ceiling)
+    if a == fnan: a = fninf
+    if b == fnan: b = finf
+    return a, b
+
+def mpi_sub(s, t, prec=0):
+    sa, sb = s
+    ta, tb = t
+    a = mpf_sub(sa, tb, prec, round_floor)
+    b = mpf_sub(sb, ta, prec, round_ceiling)
+    if a == fnan: a = fninf
+    if b == fnan: b = finf
+    return a, b
+
+def mpi_delta(s, prec):
+    sa, sb = s
+    return mpf_sub(sb, sa, prec, round_up)
+
+def mpi_mid(s, prec):
+    sa, sb = s
+    return mpf_shift(mpf_add(sa, sb, prec, round_nearest), -1)
+
+def mpi_pos(s, prec):
+    sa, sb = s
+    a = mpf_pos(sa, prec, round_floor)
+    b = mpf_pos(sb, prec, round_ceiling)
+    return a, b
+
+def mpi_neg(s, prec=0):
+    sa, sb = s
+    a = mpf_neg(sb, prec, round_floor)
+    b = mpf_neg(sa, prec, round_ceiling)
+    return a, b
+
+def mpi_abs(s, prec=0):
+    sa, sb = s
+    sas = mpf_sign(sa)
+    sbs = mpf_sign(sb)
+    # Both points nonnegative?
+    if sas >= 0:
+        a = mpf_pos(sa, prec, round_floor)
+        b = mpf_pos(sb, prec, round_ceiling)
+    # Upper point nonnegative?
+    elif sbs >= 0:
+        a = fzero
+        negsa = mpf_neg(sa)
+        if mpf_lt(negsa, sb):
+            b = mpf_pos(sb, prec, round_ceiling)
+        else:
+            b = mpf_pos(negsa, prec, round_ceiling)
+    # Both negative?
+    else:
+        a = mpf_neg(sb, prec, round_floor)
+        b = mpf_neg(sa, prec, round_ceiling)
+    return a, b
+
+# TODO: optimize
+def mpi_mul_mpf(s, t, prec):
+    return mpi_mul(s, (t, t), prec)
+
+def mpi_div_mpf(s, t, prec):
+    return mpi_div(s, (t, t), prec)
+
+def mpi_mul(s, t, prec=0):
+    sa, sb = s
+    ta, tb = t
+    sas = mpf_sign(sa)
+    sbs = mpf_sign(sb)
+    tas = mpf_sign(ta)
+    tbs = mpf_sign(tb)
+    if sas == sbs == 0:
+        # Should maybe be undefined
+        if ta == fninf or tb == finf:
+            return fninf, finf
+        return fzero, fzero
+    if tas == tbs == 0:
+        # Should maybe be undefined
+        if sa == fninf or sb == finf:
+            return fninf, finf
+        return fzero, fzero
+    if sas >= 0:
+        # positive * positive
+        if tas >= 0:
+            a = mpf_mul(sa, ta, prec, round_floor)
+            b = mpf_mul(sb, tb, prec, round_ceiling)
+            if a == fnan: a = fzero
+            if b == fnan: b = finf
+        # positive * negative
+        elif tbs <= 0:
+            a = mpf_mul(sb, ta, prec, round_floor)
+            b = mpf_mul(sa, tb, prec, round_ceiling)
+            if a == fnan: a = fninf
+            if b == fnan: b = fzero
+        # positive * both signs
+        else:
+            a = mpf_mul(sb, ta, prec, round_floor)
+            b = mpf_mul(sb, tb, prec, round_ceiling)
+            if a == fnan: a = fninf
+            if b == fnan: b = finf
+    elif sbs <= 0:
+        # negative * positive
+        if tas >= 0:
+            a = mpf_mul(sa, tb, prec, round_floor)
+            b = mpf_mul(sb, ta, prec, round_ceiling)
+            if a == fnan: a = fninf
+            if b == fnan: b = fzero
+        # negative * negative
+        elif tbs <= 0:
+            a = mpf_mul(sb, tb, prec, round_floor)
+            b = mpf_mul(sa, ta, prec, round_ceiling)
+            if a == fnan: a = fzero
+            if b == fnan: b = finf
+        # negative * both signs
+        else:
+            a = mpf_mul(sa, tb, prec, round_floor)
+            b = mpf_mul(sa, ta, prec, round_ceiling)
+            if a == fnan: a = fninf
+            if b == fnan: b = finf
+    else:
+        # General case: perform all cross-multiplications and compare
+        # Since the multiplications can be done exactly, we need only
+        # do 4 (instead of 8: two for each rounding mode)
+        cases = [mpf_mul(sa, ta), mpf_mul(sa, tb), mpf_mul(sb, ta), mpf_mul(sb, tb)]
+        if fnan in cases:
+            a, b = (fninf, finf)
+        else:
+            a, b = mpf_min_max(cases)
+            a = mpf_pos(a, prec, round_floor)
+            b = mpf_pos(b, prec, round_ceiling)
+    return a, b
+
+def mpi_square(s, prec=0):
+    sa, sb = s
+    if mpf_ge(sa, fzero):
+        a = mpf_mul(sa, sa, prec, round_floor)
+        b = mpf_mul(sb, sb, prec, round_ceiling)
+    elif mpf_le(sb, fzero):
+        a = mpf_mul(sb, sb, prec, round_floor)
+        b = mpf_mul(sa, sa, prec, round_ceiling)
+    else:
+        sa = mpf_neg(sa)
+        sa, sb = mpf_min_max([sa, sb])
+        a = fzero
+        b = mpf_mul(sb, sb, prec, round_ceiling)
+    return a, b
+
+def mpi_div(s, t, prec):
+    sa, sb = s
+    ta, tb = t
+    sas = mpf_sign(sa)
+    sbs = mpf_sign(sb)
+    tas = mpf_sign(ta)
+    tbs = mpf_sign(tb)
+    # 0 / X
+    if sas == sbs == 0:
+        # 0 / <interval containing 0>
+        if (tas < 0 and tbs > 0) or (tas == 0 or tbs == 0):
+            return fninf, finf
+        return fzero, fzero
+    # Denominator contains both negative and positive numbers;
+    # this should properly be a multi-interval, but the closest
+    # match is the entire (extended) real line
+    if tas < 0 and tbs > 0:
+        return fninf, finf
+    # Assume denominator to be nonnegative
+    if tas < 0:
+        return mpi_div(mpi_neg(s), mpi_neg(t), prec)
+    # Division by zero
+    # XXX: make sure all results make sense
+    if tas == 0:
+        # Numerator contains both signs?
+        if sas < 0 and sbs > 0:
+            return fninf, finf
+        if tas == tbs:
+            return fninf, finf
+        # Numerator positive?
+        if sas >= 0:
+            a = mpf_div(sa, tb, prec, round_floor)
+            b = finf
+        if sbs <= 0:
+            a = fninf
+            b = mpf_div(sb, tb, prec, round_ceiling)
+    # Division with positive denominator
+    # We still have to handle nans resulting from inf/0 or inf/inf
+    else:
+        # Nonnegative numerator
+        if sas >= 0:
+            a = mpf_div(sa, tb, prec, round_floor)
+            b = mpf_div(sb, ta, prec, round_ceiling)
+            if a == fnan: a = fzero
+            if b == fnan: b = finf
+        # Nonpositive numerator
+        elif sbs <= 0:
+            a = mpf_div(sa, ta, prec, round_floor)
+            b = mpf_div(sb, tb, prec, round_ceiling)
+            if a == fnan: a = fninf
+            if b == fnan: b = fzero
+        # Numerator contains both signs?
+        else:
+            a = mpf_div(sa, ta, prec, round_floor)
+            b = mpf_div(sb, ta, prec, round_ceiling)
+            if a == fnan: a = fninf
+            if b == fnan: b = finf
+    return a, b
+
+def mpi_pi(prec):
+    a = mpf_pi(prec, round_floor)
+    b = mpf_pi(prec, round_ceiling)
+    return a, b
+
+def mpi_exp(s, prec):
+    sa, sb = s
+    # exp is monotonic
+    a = mpf_exp(sa, prec, round_floor)
+    b = mpf_exp(sb, prec, round_ceiling)
+    return a, b
+
+def mpi_log(s, prec):
+    sa, sb = s
+    # log is monotonic
+    a = mpf_log(sa, prec, round_floor)
+    b = mpf_log(sb, prec, round_ceiling)
+    return a, b
+
+def mpi_sqrt(s, prec):
+    sa, sb = s
+    # sqrt is monotonic
+    a = mpf_sqrt(sa, prec, round_floor)
+    b = mpf_sqrt(sb, prec, round_ceiling)
+    return a, b
+
+def mpi_atan(s, prec):
+    sa, sb = s
+    a = mpf_atan(sa, prec, round_floor)
+    b = mpf_atan(sb, prec, round_ceiling)
+    return a, b
+
+def mpi_pow_int(s, n, prec):
+    sa, sb = s
+    if n < 0:
+        return mpi_div((fone, fone), mpi_pow_int(s, -n, prec+20), prec)
+    if n == 0:
+        return (fone, fone)
+    if n == 1:
+        return s
+    if n == 2:
+        return mpi_square(s, prec)
+    # Odd -- signs are preserved
+    if n & 1:
+        a = mpf_pow_int(sa, n, prec, round_floor)
+        b = mpf_pow_int(sb, n, prec, round_ceiling)
+    # Even -- important to ensure positivity
+    else:
+        sas = mpf_sign(sa)
+        sbs = mpf_sign(sb)
+        # Nonnegative?
+        if sas >= 0:
+            a = mpf_pow_int(sa, n, prec, round_floor)
+            b = mpf_pow_int(sb, n, prec, round_ceiling)
+        # Nonpositive?
+        elif sbs <= 0:
+            a = mpf_pow_int(sb, n, prec, round_floor)
+            b = mpf_pow_int(sa, n, prec, round_ceiling)
+        # Mixed signs?
+        else:
+            a = fzero
+            # max(-a,b)**n
+            sa = mpf_neg(sa)
+            if mpf_ge(sa, sb):
+                b = mpf_pow_int(sa, n, prec, round_ceiling)
+            else:
+                b = mpf_pow_int(sb, n, prec, round_ceiling)
+    return a, b
+
+def mpi_pow(s, t, prec):
+    ta, tb = t
+    if ta == tb and ta not in (finf, fninf):
+        if ta == from_int(to_int(ta)):
+            return mpi_pow_int(s, to_int(ta), prec)
+        if ta == fhalf:
+            return mpi_sqrt(s, prec)
+    u = mpi_log(s, prec + 20)
+    v = mpi_mul(u, t, prec + 20)
+    return mpi_exp(v, prec)
+
+def MIN(x, y):
+    if mpf_le(x, y):
+        return x
+    return y
+
+def MAX(x, y):
+    if mpf_ge(x, y):
+        return x
+    return y
+
+def cos_sin_quadrant(x, wp):
+    sign, man, exp, bc = x
+    if x == fzero:
+        return fone, fzero, 0
+    # TODO: combine evaluation code to avoid duplicate modulo
+    c, s = mpf_cos_sin(x, wp)
+    t, n, wp_ = mod_pi2(man, exp, exp+bc, 15)
+    if sign:
+        n = -1-n
+    return c, s, n
+
+def mpi_cos_sin(x, prec):
+    a, b = x
+    if a == b == fzero:
+        return (fone, fone), (fzero, fzero)
+    # Guaranteed to contain both -1 and 1
+    if (finf in x) or (fninf in x):
+        return (fnone, fone), (fnone, fone)
+    wp = prec + 20
+    ca, sa, na = cos_sin_quadrant(a, wp)
+    cb, sb, nb = cos_sin_quadrant(b, wp)
+    ca, cb = mpf_min_max([ca, cb])
+    sa, sb = mpf_min_max([sa, sb])
+    # Both functions are monotonic within one quadrant
+    if na == nb:
+        pass
+    # Guaranteed to contain both -1 and 1
+    elif nb - na >= 4:
+        return (fnone, fone), (fnone, fone)
+    else:
+        # cos has maximum between a and b
+        if na//4 != nb//4:
+            cb = fone
+        # cos has minimum
+        if (na-2)//4 != (nb-2)//4:
+            ca = fnone
+        # sin has maximum
+        if (na-1)//4 != (nb-1)//4:
+            sb = fone
+        # sin has minimum
+        if (na-3)//4 != (nb-3)//4:
+            sa = fnone
+    # Perturb to force interval rounding
+    more = from_man_exp((MPZ_ONE<<wp) + (MPZ_ONE<<10), -wp)
+    less = from_man_exp((MPZ_ONE<<wp) - (MPZ_ONE<<10), -wp)
+    def finalize(v, rounding):
+        if bool(v[0]) == (rounding == round_floor):
+            p = more
+        else:
+            p = less
+        v = mpf_mul(v, p, prec, rounding)
+        sign, man, exp, bc = v
+        if exp+bc >= 1:
+            if sign:
+                return fnone
+            return fone
+        return v
+    ca = finalize(ca, round_floor)
+    cb = finalize(cb, round_ceiling)
+    sa = finalize(sa, round_floor)
+    sb = finalize(sb, round_ceiling)
+    return (ca,cb), (sa,sb)
+
+def mpi_cos(x, prec):
+    return mpi_cos_sin(x, prec)[0]
+
+def mpi_sin(x, prec):
+    return mpi_cos_sin(x, prec)[1]
+
+def mpi_tan(x, prec):
+    cos, sin = mpi_cos_sin(x, prec+20)
+    return mpi_div(sin, cos, prec)
+
+def mpi_cot(x, prec):
+    cos, sin = mpi_cos_sin(x, prec+20)
+    return mpi_div(cos, sin, prec)
+
+def mpi_from_str_a_b(x, y, percent, prec):
+    wp = prec + 20
+    xa = from_str(x, wp, round_floor)
+    xb = from_str(x, wp, round_ceiling)
+    #ya = from_str(y, wp, round_floor)
+    y = from_str(y, wp, round_ceiling)
+    assert mpf_ge(y, fzero)
+    if percent:
+        y = mpf_mul(MAX(mpf_abs(xa), mpf_abs(xb)), y, wp, round_ceiling)
+        y = mpf_div(y, from_int(100), wp, round_ceiling)
+    a = mpf_sub(xa, y, prec, round_floor)
+    b = mpf_add(xb, y, prec, round_ceiling)
+    return a, b
+
+def mpi_from_str(s, prec):
+    """
+    Parse an interval number given as a string.
+
+    Allowed forms are
+
+    "-1.23e-27"
+        Any single decimal floating-point literal.
+    "a +- b"  or  "a (b)"
+        a is the midpoint of the interval and b is the half-width
+    "a +- b%"  or  "a (b%)"
+        a is the midpoint of the interval and the half-width
+        is b percent of a (`a \times b / 100`).
+    "[a, b]"
+        The interval indicated directly.
+    "x[y,z]e"
+        x are shared digits, y and z are unequal digits, e is the exponent.
+
+    """
+    e = ValueError("Improperly formed interval number '%s'" % s)
+    s = s.replace(" ", "")
+    wp = prec + 20
+    if "+-" in s:
+        x, y = s.split("+-")
+        return mpi_from_str_a_b(x, y, False, prec)
+    # case 2
+    elif "(" in s:
+        # Don't confuse with a complex number (x,y)
+        if s[0] == "(" or ")" not in s:
+            raise e
+        s = s.replace(")", "")
+        percent = False
+        if "%" in s:
+            if s[-1] != "%":
+                raise e
+            percent = True
+            s = s.replace("%", "")
+        x, y = s.split("(")
+        return mpi_from_str_a_b(x, y, percent, prec)
+    elif "," in s:
+        if ('[' not in s) or (']' not in s):
+            raise e
+        if s[0] == '[':
+            # case 3
+            s = s.replace("[", "")
+            s = s.replace("]", "")
+            a, b = s.split(",")
+            a = from_str(a, prec, round_floor)
+            b = from_str(b, prec, round_ceiling)
+            return a, b
+        else:
+            # case 4
+            x, y = s.split('[')
+            y, z = y.split(',')
+            if 'e' in s:
+                z, e = z.split(']')
+            else:
+                z, e = z.rstrip(']'), ''
+            a = from_str(x+y+e, prec, round_floor)
+            b = from_str(x+z+e, prec, round_ceiling)
+            return a, b
+    else:
+        a = from_str(s, prec, round_floor)
+        b = from_str(s, prec, round_ceiling)
+        return a, b
+
+def mpi_to_str(x, dps, use_spaces=True, brackets='[]', mode='brackets', error_dps=4, **kwargs):
+    """
+    Convert a mpi interval to a string.
+
+    **Arguments**
+
+    *dps*
+        decimal places to use for printing
+    *use_spaces*
+        use spaces for more readable output, defaults to true
+    *brackets*
+        pair of strings (or two-character string) giving left and right brackets
+    *mode*
+        mode of display: 'plusminus', 'percent', 'brackets' (default) or 'diff'
+    *error_dps*
+        limit the error to *error_dps* digits (mode 'plusminus and 'percent')
+
+    Additional keyword arguments are forwarded to the mpf-to-string conversion
+    for the components of the output.
+
+    **Examples**
+
+        >>> from mpmath import mpi, mp
+        >>> mp.dps = 30
+        >>> x = mpi(1, 2)._mpi_
+        >>> mpi_to_str(x, 2, mode='plusminus')
+        '1.5 +- 0.5'
+        >>> mpi_to_str(x, 2, mode='percent')
+        '1.5 (33.33%)'
+        >>> mpi_to_str(x, 2, mode='brackets')
+        '[1.0, 2.0]'
+        >>> mpi_to_str(x, 2, mode='brackets' , brackets=('<', '>'))
+        '<1.0, 2.0>'
+        >>> x = mpi('5.2582327113062393041', '5.2582327113062749951')._mpi_
+        >>> mpi_to_str(x, 15, mode='diff')
+        '5.2582327113062[4, 7]'
+        >>> mpi_to_str(mpi(0)._mpi_, 2, mode='percent')
+        '0.0 (0.0%)'
+
+    """
+    prec = dps_to_prec(dps)
+    wp = prec + 20
+    a, b = x
+    mid = mpi_mid(x, prec)
+    delta = mpi_delta(x, prec)
+    a_str = to_str(a, dps, **kwargs)
+    b_str = to_str(b, dps, **kwargs)
+    mid_str = to_str(mid, dps, **kwargs)
+    sp = ""
+    if use_spaces:
+        sp = " "
+    br1, br2 = brackets
+    if mode == 'plusminus':
+        delta_str = to_str(mpf_shift(delta,-1), dps, **kwargs)
+        s = mid_str + sp + "+-" + sp + delta_str
+    elif mode == 'percent':
+        if mid == fzero:
+            p = fzero
+        else:
+            # p = 100 * delta(x) / (2*mid(x))
+            p = mpf_mul(delta, from_int(100))
+            p = mpf_div(p, mpf_mul(mid, from_int(2)), wp)
+        s = mid_str + sp + "(" + to_str(p, error_dps) + "%)"
+    elif mode == 'brackets':
+        s = br1 + a_str + "," + sp + b_str + br2
+    elif mode == 'diff':
+        # use more digits if str(x.a) and str(x.b) are equal
+        if a_str == b_str:
+            a_str = to_str(a, dps+3, **kwargs)
+            b_str = to_str(b, dps+3, **kwargs)
+        # separate mantissa and exponent
+        a = a_str.split('e')
+        if len(a) == 1:
+            a.append('')
+        b = b_str.split('e')
+        if len(b) == 1:
+            b.append('')
+        if a[1] == b[1]:
+            if a[0] != b[0]:
+                for i in xrange(len(a[0]) + 1):
+                    if a[0][i] != b[0][i]:
+                        break
+                s = (a[0][:i] + br1 + a[0][i:] + ',' + sp + b[0][i:] + br2
+                     + 'e'*min(len(a[1]), 1) + a[1])
+            else: # no difference
+                s = a[0] + br1 + br2 + 'e'*min(len(a[1]), 1) + a[1]
+        else:
+            s = br1 + 'e'.join(a) + ',' + sp + 'e'.join(b) + br2
+    else:
+        raise ValueError("'%s' is unknown mode for printing mpi" % mode)
+    return s
+
+def mpci_add(x, y, prec):
+    a, b = x
+    c, d = y
+    return mpi_add(a, c, prec), mpi_add(b, d, prec)
+
+def mpci_sub(x, y, prec):
+    a, b = x
+    c, d = y
+    return mpi_sub(a, c, prec), mpi_sub(b, d, prec)
+
+def mpci_neg(x, prec=0):
+    a, b = x
+    return mpi_neg(a, prec), mpi_neg(b, prec)
+
+def mpci_pos(x, prec):
+    a, b = x
+    return mpi_pos(a, prec), mpi_pos(b, prec)
+
+def mpci_mul(x, y, prec):
+    # TODO: optimize for real/imag cases
+    a, b = x
+    c, d = y
+    r1 = mpi_mul(a,c)
+    r2 = mpi_mul(b,d)
+    re = mpi_sub(r1,r2,prec)
+    i1 = mpi_mul(a,d)
+    i2 = mpi_mul(b,c)
+    im = mpi_add(i1,i2,prec)
+    return re, im
+
+def mpci_div(x, y, prec):
+    # TODO: optimize for real/imag cases
+    a, b = x
+    c, d = y
+    wp = prec+20
+    m1 = mpi_square(c)
+    m2 = mpi_square(d)
+    m = mpi_add(m1,m2,wp)
+    re = mpi_add(mpi_mul(a,c), mpi_mul(b,d), wp)
+    im = mpi_sub(mpi_mul(b,c), mpi_mul(a,d), wp)
+    re = mpi_div(re, m, prec)
+    im = mpi_div(im, m, prec)
+    return re, im
+
+def mpci_exp(x, prec):
+    a, b = x
+    wp = prec+20
+    r = mpi_exp(a, wp)
+    c, s = mpi_cos_sin(b, wp)
+    a = mpi_mul(r, c, prec)
+    b = mpi_mul(r, s, prec)
+    return a, b
+
+def mpi_shift(x, n):
+    a, b = x
+    return mpf_shift(a,n), mpf_shift(b,n)
+
+def mpi_cosh_sinh(x, prec):
+    # TODO: accuracy for small x
+    wp = prec+20
+    e1 = mpi_exp(x, wp)
+    e2 = mpi_div(mpi_one, e1, wp)
+    c = mpi_add(e1, e2, prec)
+    s = mpi_sub(e1, e2, prec)
+    c = mpi_shift(c, -1)
+    s = mpi_shift(s, -1)
+    return c, s
+
+def mpci_cos(x, prec):
+    a, b = x
+    wp = prec+10
+    c, s = mpi_cos_sin(a, wp)
+    ch, sh = mpi_cosh_sinh(b, wp)
+    re = mpi_mul(c, ch, prec)
+    im = mpi_mul(s, sh, prec)
+    return re, mpi_neg(im)
+
+def mpci_sin(x, prec):
+    a, b = x
+    wp = prec+10
+    c, s = mpi_cos_sin(a, wp)
+    ch, sh = mpi_cosh_sinh(b, wp)
+    re = mpi_mul(s, ch, prec)
+    im = mpi_mul(c, sh, prec)
+    return re, im
+
+def mpci_abs(x, prec):
+    a, b = x
+    if a == mpi_zero:
+        return mpi_abs(b)
+    if b == mpi_zero:
+        return mpi_abs(a)
+    # Important: nonnegative
+    a = mpi_square(a)
+    b = mpi_square(b)
+    t = mpi_add(a, b, prec+20)
+    return mpi_sqrt(t, prec)
+
+def mpi_atan2(y, x, prec):
+    ya, yb = y
+    xa, xb = x
+    # Constrained to the real line
+    if ya == yb == fzero:
+        if mpf_ge(xa, fzero):
+            return mpi_zero
+        return mpi_pi(prec)
+    # Right half-plane
+    if mpf_ge(xa, fzero):
+        if mpf_ge(ya, fzero):
+            a = mpf_atan2(ya, xb, prec, round_floor)
+        else:
+            a = mpf_atan2(ya, xa, prec, round_floor)
+        if mpf_ge(yb, fzero):
+            b = mpf_atan2(yb, xa, prec, round_ceiling)
+        else:
+            b = mpf_atan2(yb, xb, prec, round_ceiling)
+    # Upper half-plane
+    elif mpf_ge(ya, fzero):
+        b = mpf_atan2(ya, xa, prec, round_ceiling)
+        if mpf_le(xb, fzero):
+            a = mpf_atan2(yb, xb, prec, round_floor)
+        else:
+            a = mpf_atan2(ya, xb, prec, round_floor)
+    # Lower half-plane
+    elif mpf_le(yb, fzero):
+        a = mpf_atan2(yb, xa, prec, round_floor)
+        if mpf_le(xb, fzero):
+            b = mpf_atan2(ya, xb, prec, round_ceiling)
+        else:
+            b = mpf_atan2(yb, xb, prec, round_ceiling)
+    # Covering the origin
+    else:
+        b = mpf_pi(prec, round_ceiling)
+        a = mpf_neg(b)
+    return a, b
+
+def mpci_arg(z, prec):
+    x, y = z
+    return mpi_atan2(y, x, prec)
+
+def mpci_log(z, prec):
+    x, y = z
+    re = mpi_log(mpci_abs(z, prec+20), prec)
+    im = mpci_arg(z, prec)
+    return re, im
+
+def mpci_pow(x, y, prec):
+    # TODO: recognize/speed up real cases, integer y
+    yre, yim = y
+    if yim == mpi_zero:
+        ya, yb = yre
+        if ya == yb:
+            sign, man, exp, bc = yb
+            if man and exp >= 0:
+                return mpci_pow_int(x, (-1)**sign * int(man<<exp), prec)
+            # x^0
+            if yb == fzero:
+                return mpci_pow_int(x, 0, prec)
+    wp = prec+20
+    return mpci_exp(mpci_mul(y, mpci_log(x, wp), wp), prec)
+
+def mpci_square(x, prec):
+    a, b = x
+    # (a+bi)^2 = (a^2-b^2) + 2abi
+    re = mpi_sub(mpi_square(a), mpi_square(b), prec)
+    im = mpi_mul(a, b, prec)
+    im = mpi_shift(im, 1)
+    return re, im
+
+def mpci_pow_int(x, n, prec):
+    if n < 0:
+        return mpci_div((mpi_one,mpi_zero), mpci_pow_int(x, -n, prec+20), prec)
+    if n == 0:
+        return mpi_one, mpi_zero
+    if n == 1:
+        return mpci_pos(x, prec)
+    if n == 2:
+        return mpci_square(x, prec)
+    wp = prec + 20
+    result = (mpi_one, mpi_zero)
+    while n:
+        if n & 1:
+            result = mpci_mul(result, x, wp)
+            n -= 1
+        x = mpci_square(x, wp)
+        n >>= 1
+    return mpci_pos(result, prec)
+
+gamma_min_a = from_float(1.46163214496)
+gamma_min_b = from_float(1.46163214497)
+gamma_min = (gamma_min_a, gamma_min_b)
+gamma_mono_imag_a = from_float(-1.1)
+gamma_mono_imag_b = from_float(1.1)
+
+def mpi_overlap(x, y):
+    a, b = x
+    c, d = y
+    if mpf_lt(d, a): return False
+    if mpf_gt(c, b): return False
+    return True
+
+# type = 0 -- gamma
+# type = 1 -- factorial
+# type = 2 -- 1/gamma
+# type = 3 -- log-gamma
+
+def mpi_gamma(z, prec, type=0):
+    a, b = z
+    wp = prec+20
+
+    if type == 1:
+        return mpi_gamma(mpi_add(z, mpi_one, wp), prec, 0)
+
+    # increasing
+    if mpf_gt(a, gamma_min_b):
+        if type == 0:
+            c = mpf_gamma(a, prec, round_floor)
+            d = mpf_gamma(b, prec, round_ceiling)
+        elif type == 2:
+            c = mpf_rgamma(b, prec, round_floor)
+            d = mpf_rgamma(a, prec, round_ceiling)
+        elif type == 3:
+            c = mpf_loggamma(a, prec, round_floor)
+            d = mpf_loggamma(b, prec, round_ceiling)
+    # decreasing
+    elif mpf_gt(a, fzero) and mpf_lt(b, gamma_min_a):
+        if type == 0:
+            c = mpf_gamma(b, prec, round_floor)
+            d = mpf_gamma(a, prec, round_ceiling)
+        elif type == 2:
+            c = mpf_rgamma(a, prec, round_floor)
+            d = mpf_rgamma(b, prec, round_ceiling)
+        elif type == 3:
+            c = mpf_loggamma(b, prec, round_floor)
+            d = mpf_loggamma(a, prec, round_ceiling)
+    else:
+        # TODO: reflection formula
+        znew = mpi_add(z, mpi_one, wp)
+        if type == 0: return mpi_div(mpi_gamma(znew, prec+2, 0), z, prec)
+        if type == 2: return mpi_mul(mpi_gamma(znew, prec+2, 2), z, prec)
+        if type == 3: return mpi_sub(mpi_gamma(znew, prec+2, 3), mpi_log(z, prec+2), prec)
+    return c, d
+
+def mpci_gamma(z, prec, type=0):
+    (a1,a2), (b1,b2) = z
+
+    # Real case
+    if b1 == b2 == fzero and (type != 3 or mpf_gt(a1,fzero)):
+        return mpi_gamma(z, prec, type), mpi_zero
+
+    # Estimate precision
+    wp = prec+20
+    if type != 3:
+        amag = a2[2]+a2[3]
+        bmag = b2[2]+b2[3]
+        if a2 != fzero:
+            mag = max(amag, bmag)
+        else:
+            mag = bmag
+        an = abs(to_int(a2))
+        bn = abs(to_int(b2))
+        absn = max(an, bn)
+        gamma_size = max(0,absn*mag)
+        wp += bitcount(gamma_size)
+
+    # Assume type != 1
+    if type == 1:
+        (a1,a2) = mpi_add((a1,a2), mpi_one, wp); z = (a1,a2), (b1,b2)
+        type = 0
+
+    # Avoid non-monotonic region near the negative real axis
+    if mpf_lt(a1, gamma_min_b):
+        if mpi_overlap((b1,b2), (gamma_mono_imag_a, gamma_mono_imag_b)):
+            # TODO: reflection formula
+            #if mpf_lt(a2, mpf_shift(fone,-1)):
+            #    znew = mpci_sub((mpi_one,mpi_zero),z,wp)
+            #    ...
+            # Recurrence:
+            # gamma(z) = gamma(z+1)/z
+            znew = mpi_add((a1,a2), mpi_one, wp), (b1,b2)
+            if type == 0: return mpci_div(mpci_gamma(znew, prec+2, 0), z, prec)
+            if type == 2: return mpci_mul(mpci_gamma(znew, prec+2, 2), z, prec)
+            if type == 3: return mpci_sub(mpci_gamma(znew, prec+2, 3), mpci_log(z,prec+2), prec)
+
+    # Use monotonicity (except for a small region close to the
+    # origin and near poles)
+    # upper half-plane
+    if mpf_ge(b1, fzero):
+        minre = mpc_loggamma((a1,b2), wp, round_floor)
+        maxre = mpc_loggamma((a2,b1), wp, round_ceiling)
+        minim = mpc_loggamma((a1,b1), wp, round_floor)
+        maxim = mpc_loggamma((a2,b2), wp, round_ceiling)
+    # lower half-plane
+    elif mpf_le(b2, fzero):
+        minre = mpc_loggamma((a1,b1), wp, round_floor)
+        maxre = mpc_loggamma((a2,b2), wp, round_ceiling)
+        minim = mpc_loggamma((a2,b1), wp, round_floor)
+        maxim = mpc_loggamma((a1,b2), wp, round_ceiling)
+    # crosses real axis
+    else:
+        maxre = mpc_loggamma((a2,fzero), wp, round_ceiling)
+        # stretches more into the lower half-plane
+        if mpf_gt(mpf_neg(b1), b2):
+            minre = mpc_loggamma((a1,b1), wp, round_ceiling)
+        else:
+            minre = mpc_loggamma((a1,b2), wp, round_ceiling)
+        minim = mpc_loggamma((a2,b1), wp, round_floor)
+        maxim = mpc_loggamma((a2,b2), wp, round_floor)
+
+    w = (minre[0], maxre[0]), (minim[1], maxim[1])
+    if type == 3:
+        return mpi_pos(w[0], prec), mpi_pos(w[1], prec)
+    if type == 2:
+        w = mpci_neg(w)
+    return mpci_exp(w, prec)
+
+def mpi_loggamma(z, prec): return mpi_gamma(z, prec, type=3)
+def mpci_loggamma(z, prec): return mpci_gamma(z, prec, type=3)
+
+def mpi_rgamma(z, prec): return mpi_gamma(z, prec, type=2)
+def mpci_rgamma(z, prec): return mpci_gamma(z, prec, type=2)
+
+def mpi_factorial(z, prec): return mpi_gamma(z, prec, type=1)
+def mpci_factorial(z, prec): return mpci_gamma(z, prec, type=1)