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""" Machine limits for Float32 and Float64 and (long double) if available...
"""
__all__ = ['finfo','iinfo']
from machar import MachAr
import numpy.core.numeric as numeric
import numpy.core.numerictypes as ntypes
from numpy.core.numeric import array
import numpy as np
def _frz(a):
"""fix rank-0 --> rank-1"""
if a.ndim == 0: a.shape = (1,)
return a
_convert_to_float = {
ntypes.csingle: ntypes.single,
ntypes.complex_: ntypes.float_,
ntypes.clongfloat: ntypes.longfloat
}
class finfo(object):
"""
finfo(dtype)
Machine limits for floating point types.
Attributes
----------
eps : floating point number of the appropriate type
The smallest representable number such that ``1.0 + eps != 1.0``.
epsneg : floating point number of the appropriate type
The smallest representable number such that ``1.0 - epsneg != 1.0``.
iexp : int
The number of bits in the exponent portion of the floating point
representation.
machar : MachAr
The object which calculated these parameters and holds more detailed
information.
machep : int
The exponent that yields ``eps``.
max : floating point number of the appropriate type
The largest representable number.
maxexp : int
The smallest positive power of the base (2) that causes overflow.
min : floating point number of the appropriate type
The smallest representable number, typically ``-max``.
minexp : int
The most negative power of the base (2) consistent with there being
no leading 0s in the mantissa.
negep : int
The exponent that yields ``epsneg``.
nexp : int
The number of bits in the exponent including its sign and bias.
nmant : int
The number of bits in the mantissa.
precision : int
The approximate number of decimal digits to which this kind of float
is precise.
resolution : floating point number of the appropriate type
The approximate decimal resolution of this type, i.e.
``10**-precision``.
tiny : floating point number of the appropriate type
The smallest-magnitude usable number.
Parameters
----------
dtype : floating point type, dtype, or instance
The kind of floating point data type to get information about.
See Also
--------
numpy.lib.machar.MachAr :
The implementation of the tests that produce this information.
iinfo :
The equivalent for integer data types.
Notes
-----
For developers of numpy: do not instantiate this at the module level. The
initial calculation of these parameters is expensive and negatively impacts
import times. These objects are cached, so calling ``finfo()`` repeatedly
inside your functions is not a problem.
"""
_finfo_cache = {}
def __new__(cls, dtype):
obj = cls._finfo_cache.get(dtype,None)
if obj is not None:
return obj
dtypes = [dtype]
newdtype = numeric.obj2sctype(dtype)
if newdtype is not dtype:
dtypes.append(newdtype)
dtype = newdtype
if not issubclass(dtype, numeric.inexact):
raise ValueError, "data type %r not inexact" % (dtype)
obj = cls._finfo_cache.get(dtype,None)
if obj is not None:
return obj
if not issubclass(dtype, numeric.floating):
newdtype = _convert_to_float[dtype]
if newdtype is not dtype:
dtypes.append(newdtype)
dtype = newdtype
obj = cls._finfo_cache.get(dtype,None)
if obj is not None:
return obj
obj = object.__new__(cls)._init(dtype)
for dt in dtypes:
cls._finfo_cache[dt] = obj
return obj
def _init(self, dtype):
self.dtype = dtype
if dtype is ntypes.double:
itype = ntypes.int64
fmt = '%24.16e'
precname = 'double'
elif dtype is ntypes.single:
itype = ntypes.int32
fmt = '%15.7e'
precname = 'single'
elif dtype is ntypes.longdouble:
itype = ntypes.longlong
fmt = '%s'
precname = 'long double'
else:
raise ValueError, repr(dtype)
machar = MachAr(lambda v:array([v], dtype),
lambda v:_frz(v.astype(itype))[0],
lambda v:array(_frz(v)[0], dtype),
lambda v: fmt % array(_frz(v)[0], dtype),
'numpy %s precision floating point number' % precname)
for word in ['precision', 'iexp',
'maxexp','minexp','negep',
'machep']:
setattr(self,word,getattr(machar, word))
for word in ['tiny','resolution','epsneg']:
setattr(self,word,getattr(machar, word).squeeze())
self.max = machar.huge.flat[0]
self.min = -self.max
self.eps = machar.eps.flat[0]
self.nexp = machar.iexp
self.nmant = machar.it
self.machar = machar
self._str_tiny = machar._str_xmin
self._str_max = machar._str_xmax
self._str_epsneg = machar._str_epsneg
self._str_eps = machar._str_eps
self._str_resolution = machar._str_resolution
return self
def __str__(self):
return '''\
Machine parameters for %(dtype)s
---------------------------------------------------------------------
precision=%(precision)3s resolution=%(_str_resolution)s
machep=%(machep)6s eps= %(_str_eps)s
negep =%(negep)6s epsneg= %(_str_epsneg)s
minexp=%(minexp)6s tiny= %(_str_tiny)s
maxexp=%(maxexp)6s max= %(_str_max)s
nexp =%(nexp)6s min= -max
---------------------------------------------------------------------
''' % self.__dict__
class iinfo:
"""
iinfo(type)
Machine limits for integer types.
Attributes
----------
min : int
The smallest integer expressible by the type.
max : int
The largest integer expressible by the type.
Parameters
----------
type : integer type, dtype, or instance
The kind of integer data type to get information about.
See Also
--------
finfo : The equivalent for floating point data types.
Examples
--------
With types:
>>> ii16 = np.iinfo(np.int16)
>>> ii16.min
-32768
>>> ii16.max
32767
>>> ii32 = np.iinfo(np.int32)
>>> ii32.min
-2147483648
>>> ii32.max
2147483647
With instances:
>>> ii32 = np.iinfo(np.int32(10))
>>> ii32.min
-2147483648
>>> ii32.max
2147483647
"""
_min_vals = {}
_max_vals = {}
def __init__(self, type):
self.dtype = np.dtype(type)
self.kind = self.dtype.kind
self.bits = self.dtype.itemsize * 8
self.key = "%s%d" % (self.kind, self.bits)
if not self.kind in 'iu':
raise ValueError("Invalid integer data type.")
def min(self):
"""Minimum value of given dtype."""
if self.kind == 'u':
return 0
else:
try:
val = iinfo._min_vals[self.key]
except KeyError:
val = int(-(1L << (self.bits-1)))
iinfo._min_vals[self.key] = val
return val
min = property(min)
def max(self):
"""Maximum value of given dtype."""
try:
val = iinfo._max_vals[self.key]
except KeyError:
if self.kind == 'u':
val = int((1L << self.bits) - 1)
else:
val = int((1L << (self.bits-1)) - 1)
iinfo._max_vals[self.key] = val
return val
max = property(max)
if __name__ == '__main__':
f = finfo(ntypes.single)
print 'single epsilon:',f.eps
print 'single tiny:',f.tiny
f = finfo(ntypes.float)
print 'float epsilon:',f.eps
print 'float tiny:',f.tiny
f = finfo(ntypes.longfloat)
print 'longfloat epsilon:',f.eps
print 'longfloat tiny:',f.tiny
|
