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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):
"""Machine limits for floating point types.
:Parameters:
dtype : floating point type or instance
:SeeAlso:
- numpy.lib.machar.MachAr
"""
_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:
"""Limits for integer types.
:Parameters:
type : integer type or instance
"""
_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
|
