def mag(ctx, x):
"""
Quick logarithmic magnitude estimate of a number.
Returns an integer or infinity `m` such that `|x| <= 2^m`.
It is not guaranteed that `m` is an optimal bound,
but it will never be off by more than 2 (and probably not
more than 1).
"""
if hasattr(x, "_mpf_"):
return ctx._mpf_mag(x._mpf_)
elif hasattr(x, "_mpc_"):
r, i = x._mpc_
if r == fzero:
return ctx._mpf_mag(i)
if i == fzero:
return ctx._mpf_mag(r)
return 1 + max(ctx._mpf_mag(r), ctx._mpf_mag(i))
elif isinstance(x, int_types):
if x:
return bitcount(abs(x))
return ctx.ninf
elif isinstance(x, rational.mpq):
p, q = x
if p:
return 1 + bitcount(abs(p)) - bitcount(abs(q))
return ctx.ninf
else:
x = ctx.convert(x)
if hasattr(x, "_mpf_") or hasattr(x, "_mpc_"):
return ctx.mag(x)
else:
raise TypeError("requires an mpf/mpc")
def mag(ctx, x):
"""
Quick logarithmic magnitude estimate of a number.
Returns an integer or infinity `m` such that `|x| <= 2^m`.
It is not guaranteed that `m` is an optimal bound,
but it will never be off by more than 2 (and probably not
more than 1).
"""
if hasattr(x, "_mpf_"):
return ctx._mpf_mag(x._mpf_)
elif hasattr(x, "_mpc_"):
r, i = x._mpc_
if r == fzero:
return ctx._mpf_mag(i)
if i == fzero:
return ctx._mpf_mag(r)
return 1+max(ctx._mpf_mag(r), ctx._mpf_mag(i))
elif isinstance(x, int_types):
if x:
return bitcount(abs(x))
return ctx.ninf
elif isinstance(x, rational.mpq):
p, q = x
if p:
return 1 + bitcount(abs(p)) - bitcount(abs(q))
return ctx.ninf
else:
x = ctx.convert(x)
if hasattr(x, "_mpf_") or hasattr(x, "_mpc_"):
return ctx.mag(x)
else:
raise TypeError("requires an mpf/mpc")
def __hash__(s):
a, b = s._mpq_
if b == 1:
return hash(a)
# Power of two: mpf compatible hash
if not (b & (b - 1)):
return mpf_hash(from_man_exp(a, 1 - bitcount(b)))
return hash((a, b))
def __hash__(s):
a, b = s._mpq_
if b == 1:
return hash(a)
# Power of two: mpf compatible hash
if not (b & (b-1)):
return mpf_hash(from_man_exp(a, 1-bitcount(b)))
return hash((a,b))
def mag(ctx, x):
"""
Quick logarithmic magnitude estimate of a number. Returns an
integer or infinity `m` such that `|x| <= 2^m`. It is not
guaranteed that `m` is an optimal bound, but it will never
be too large by more than 2 (and probably not more than 1).
**Examples**
>>> from mpmath import *
>>> mp.pretty = True
>>> mag(10), mag(10.0), mag(mpf(10)), int(ceil(log(10,2)))
(4, 4, 4, 4)
>>> mag(10j), mag(10+10j)
(4, 5)
>>> mag(0.01), int(ceil(log(0.01,2)))
(-6, -6)
>>> mag(0), mag(inf), mag(-inf), mag(nan)
(-inf, +inf, +inf, nan)
"""
if hasattr(x, "_mpf_"):
return ctx._mpf_mag(x._mpf_)
elif hasattr(x, "_mpc_"):
r, i = x._mpc_
if r == fzero:
return ctx._mpf_mag(i)
if i == fzero:
return ctx._mpf_mag(r)
return 1+max(ctx._mpf_mag(r), ctx._mpf_mag(i))
elif isinstance(x, int_types):
if x:
return bitcount(abs(x))
return ctx.ninf
elif isinstance(x, rational.mpq):
p, q = x._mpq_
if p:
return 1 + bitcount(abs(p)) - bitcount(q)
return ctx.ninf
else:
x = ctx.convert(x)
if hasattr(x, "_mpf_") or hasattr(x, "_mpc_"):
return ctx.mag(x)
else:
raise TypeError("requires an mpf/mpc")
def mag(ctx, x):
"""
Quick logarithmic magnitude estimate of a number. Returns an
integer or infinity `m` such that `|x| <= 2^m`. It is not
guaranteed that `m` is an optimal bound, but it will never
be too large by more than 2 (and probably not more than 1).
**Examples**
>>> from mpmath import *
>>> mp.pretty = True
>>> mag(10), mag(10.0), mag(mpf(10)), int(ceil(log(10,2)))
(4, 4, 4, 4)
>>> mag(10j), mag(10+10j)
(4, 5)
>>> mag(0.01), int(ceil(log(0.01,2)))
(-6, -6)
>>> mag(0), mag(inf), mag(-inf), mag(nan)
(-inf, +inf, +inf, nan)
"""
if hasattr(x, "_mpf_"):
return ctx._mpf_mag(x._mpf_)
elif hasattr(x, "_mpc_"):
r, i = x._mpc_
if r == fzero:
return ctx._mpf_mag(i)
if i == fzero:
return ctx._mpf_mag(r)
return 1 + max(ctx._mpf_mag(r), ctx._mpf_mag(i))
elif isinstance(x, int_types):
if x:
return bitcount(abs(x))
return ctx.ninf
elif isinstance(x, rational.mpq):
p, q = x._mpq_
if p:
return 1 + bitcount(abs(p)) - bitcount(q)
return ctx.ninf
else:
x = ctx.convert(x)
if hasattr(x, "_mpf_") or hasattr(x, "_mpc_"):
return ctx.mag(x)
else:
raise TypeError("requires an mpf/mpc")
def nint_distance(ctx, x):
"""
Returns (n, d) where n is the nearest integer to x and d is the
log-2 distance (i.e. distance in bits) of n from x. If d < 0,
(-d) gives the bits of cancellation when n is subtracted from x.
This function is intended to be used to check for cancellation
at poles.
"""
if hasattr(x, "_mpf_"):
re = x._mpf_
im_dist = ctx.ninf
elif hasattr(x, "_mpc_"):
re, im = x._mpc_
isign, iman, iexp, ibc = im
if iman:
im_dist = iexp + ibc
elif im == fzero:
im_dist = ctx.ninf
else:
raise ValueError("requires a finite number")
elif isinstance(x, int_types):
return int(x), ctx.ninf
elif isinstance(x, rational.mpq):
p, q = x
n, r = divmod(p, q)
if 2*r >= q:
n += 1
elif not r:
return n, ctx.ninf
# log(p/q-n) = log((p-nq)/q) = log(p-nq) - log(q)
d = bitcount(abs(p-n*q)) - bitcount(q)
return n, d
else:
x = ctx.convert(x)
if hasattr(x, "_mpf_") or hasattr(x, "_mpc_"):
return ctx.nint_distance(x)
else:
raise TypeError("requires an mpf/mpc")
sign, man, exp, bc = re
shift = exp+bc
if sign:
man = -man
if shift < -1:
n = 0
re_dist = shift
elif man:
if exp >= 0:
n = man << exp
re_dist = ctx.ninf
else:
if shift >= 0:
xfixed = man << shift
else:
xfixed = man >> (-shift)
n1 = xfixed >> bc
n2 = -((-xfixed) >> bc)
dist1 = abs(xfixed - (n1<<bc))
dist2 = abs(xfixed - (n2<<bc))
if dist1 < dist2:
re_dist = dist1
n = n1
else:
re_dist = dist2
n = n2
if re_dist:
re_dist = bitcount(re_dist) - bc
else:
re_dist = ctx.ninf
elif re == fzero:
re_dist = ctx.ninf
n = 0
else:
raise ValueError("requires a finite number")
return n, max(re_dist, im_dist)
def nint_distance(ctx, x):
r"""
Return `(n,d)` where `n` is the nearest integer to `x` and `d` is
an estimate of `\log_2(|x-n|)`. If `d < 0`, `-d` gives the precision
(measured in bits) lost to cancellation when computing `x-n`.
>>> from mpmath import *
>>> n, d = nint_distance(5)
>>> print n, d
5 -inf
>>> n, d = nint_distance(mpf(5))
>>> print n, d
5 -inf
>>> n, d = nint_distance(mpf(5.00000001))
>>> print n, d
5 -26
>>> n, d = nint_distance(mpf(4.99999999))
>>> print n, d
5 -26
>>> n, d = nint_distance(mpc(5,10))
>>> print n, d
5 4
>>> n, d = nint_distance(mpc(5,0.000001))
>>> print n, d
5 -19
"""
if hasattr(x, "_mpf_"):
re = x._mpf_
im_dist = ctx.ninf
elif hasattr(x, "_mpc_"):
re, im = x._mpc_
isign, iman, iexp, ibc = im
if iman:
im_dist = iexp + ibc
elif im == fzero:
im_dist = ctx.ninf
else:
raise ValueError("requires a finite number")
elif isinstance(x, int_types):
return int(x), ctx.ninf
elif isinstance(x, rational.mpq):
p, q = x._mpq_
n, r = divmod(p, q)
if 2*r >= q:
n += 1
elif not r:
return n, ctx.ninf
# log(p/q-n) = log((p-nq)/q) = log(p-nq) - log(q)
d = bitcount(abs(p-n*q)) - bitcount(q)
return n, d
else:
x = ctx.convert(x)
if hasattr(x, "_mpf_") or hasattr(x, "_mpc_"):
return ctx.nint_distance(x)
else:
raise TypeError("requires an mpf/mpc")
sign, man, exp, bc = re
shift = exp+bc
if sign:
man = -man
if shift < -1:
n = 0
re_dist = shift
elif man:
if exp >= 0:
n = man << exp
re_dist = ctx.ninf
else:
if shift >= 0:
xfixed = man << shift
else:
xfixed = man >> (-shift)
n1 = xfixed >> bc
n2 = -((-xfixed) >> bc)
dist1 = abs(xfixed - (n1<<bc))
dist2 = abs(xfixed - (n2<<bc))
if dist1 < dist2:
re_dist = dist1
n = n1
else:
re_dist = dist2
n = n2
if re_dist:
re_dist = bitcount(re_dist) - bc
else:
re_dist = ctx.ninf
elif re == fzero:
re_dist = ctx.ninf
n = 0
else:
raise ValueError("requires a finite number")
return n, max(re_dist, im_dist)
def nint_distance(ctx, x):
r"""
Return `(n,d)` where `n` is the nearest integer to `x` and `d` is
an estimate of `\log_2(|x-n|)`. If `d < 0`, `-d` gives the precision
(measured in bits) lost to cancellation when computing `x-n`.
>>> from mpmath import *
>>> n, d = nint_distance(5)
>>> print n, d
5 -inf
>>> n, d = nint_distance(mpf(5))
>>> print n, d
5 -inf
>>> n, d = nint_distance(mpf(5.00000001))
>>> print n, d
5 -26
>>> n, d = nint_distance(mpf(4.99999999))
>>> print n, d
5 -26
>>> n, d = nint_distance(mpc(5,10))
>>> print n, d
5 4
>>> n, d = nint_distance(mpc(5,0.000001))
>>> print n, d
5 -19
"""
typx = type(x)
if typx in int_types:
return int(x), ctx.ninf
elif typx is rational.mpq:
p, q = x._mpq_
n, r = divmod(p, q)
if 2*r >= q:
n += 1
elif not r:
return n, ctx.ninf
# log(p/q-n) = log((p-nq)/q) = log(p-nq) - log(q)
d = bitcount(abs(p-n*q)) - bitcount(q)
return n, d
if hasattr(x, "_mpf_"):
re = x._mpf_
im_dist = ctx.ninf
elif hasattr(x, "_mpc_"):
re, im = x._mpc_
isign, iman, iexp, ibc = im
if iman:
im_dist = iexp + ibc
elif im == fzero:
im_dist = ctx.ninf
else:
raise ValueError("requires a finite number")
else:
x = ctx.convert(x)
if hasattr(x, "_mpf_") or hasattr(x, "_mpc_"):
return ctx.nint_distance(x)
else:
raise TypeError("requires an mpf/mpc")
sign, man, exp, bc = re
mag = exp+bc
# |x| < 0.5
if mag < 0:
n = 0
re_dist = mag
elif man:
# exact integer
if exp >= 0:
n = man << exp
re_dist = ctx.ninf
# exact half-integer
elif exp == -1:
n = (man>>1)+1
re_dist = 0
else:
d = (-exp-1)
t = man >> d
if t & 1:
t += 1
man = (t<<d) - man
else:
man -= (t<<d)
n = t>>1 # int(t)>>1
re_dist = exp+bitcount(man)
if sign:
n = -n
elif re == fzero:
re_dist = ctx.ninf
n = 0
else:
raise ValueError("requires a finite number")
return n, max(re_dist, im_dist)
