Multiple-precision Reals

gmpy2 replaces the mpf type from gmpy 1.x with a new mpfr type based on the MPFR library. The new mpfr type supports correct rounding, selectable rounding modes, and many trigonometric, exponential, and special functions. A context manager is used to control precision, rounding modes, and the behavior of exceptions.

The default precision of an mpfr is 53 bits - the same precision as Python’s float type. If the precison is changed, then mpfr(float('1.2')) differs from mpfr('1.2'). To take advantage of the higher precision provided by the mpfr type, always pass constants as strings.

>>> import gmpy2
>>> from gmpy2 import mpfr
>>> mpfr('1.2')
mpfr('1.2')
>>> mpfr(float('1.2'))
mpfr('1.2')
>>> gmpy2.get_context().precision=100
>>> mpfr('1.2')
mpfr('1.2000000000000000000000000000006',100)
>>> mpfr(float('1.2'))
mpfr('1.1999999999999999555910790149937',100)
>>>

Contexts

Warning

Contexts and context managers are not thread-safe! Modifying the context in one thread will impact all other threads.

A context is used to control the behavior of mpfr and mpc arithmetic. In addition to controlling the precision, the rounding mode can be specified, minimum and maximum exponent values can be changed, various exceptions can be raised or ignored, gradual underflow can be enabled, and returning complex results can be enabled.

gmpy2.context() creates a new context with all options set to default. gmpy2.set_context(ctx) will set the active context to ctx. gmpy2.get_context() will return a reference to the active context. Note that contexts are mutable: modifying the reference returned by get_context() will modify the active context until a new context is enabled with set_context(). The copy() method of a context will return a copy of the context.

The following example just modifies the precision. The remaining options will be discussed later.

>>> gmpy2.set_context(gmpy2.context())
>>> gmpy2.get_context()
context(precision=53, real_prec=Default, imag_prec=Default,
        round=RoundToNearest, real_round=Default, imag_round=Default,
        emax=1073741823, emin=-1073741823,
        subnormalize=False,
        trap_underflow=False, underflow=False,
        trap_overflow=False, overflow=False,
        trap_inexact=False, inexact=False,
        trap_invalid=False, invalid=False,
        trap_erange=False, erange=False,
        trap_divzero=False, divzero=False,
        trap_expbound=False,
        allow_complex=False)
>>> gmpy2.sqrt(5)
mpfr('2.2360679774997898')
>>> gmpy2.get_context().precision=100
>>> gmpy2.sqrt(5)
mpfr('2.2360679774997896964091736687316',100)
>>> gmpy2.get_context().precision+=20
>>> gmpy2.sqrt(5)
mpfr('2.2360679774997896964091736687312762351',120)
>>> ctx=gmpy2.get_context()
>>> ctx.precision+=20
>>> gmpy2.sqrt(5)
mpfr('2.2360679774997896964091736687312762354406182',140)
>>> gmpy2.set_context(gmpy2.context())
>>> gmpy2.sqrt(5)
mpfr('2.2360679774997898')
>>> ctx.precision+=20
>>> gmpy2.sqrt(5)
mpfr('2.2360679774997898')
>>> gmpy2.set_context(ctx)
>>> gmpy2.sqrt(5)
mpfr('2.2360679774997896964091736687312762354406183596116',160)
>>>

Context Attributes

precision
This attribute controls the precision of an mpfr result. The precision is specified in bits, not decimal digits. The maximum precision that can be specified is platform dependent and can be retrieved with get_max_precision().

Note

Specifying a value for precision that is too close to the maximum precision will cause the MPFR library to fail.

real_prec
This attribute controls the precision of the real part of an mpc result. If the value is Default, then the value of the precision attribute is used.
imag_prec
This attribute controls the precision of the imaginary part of an mpc result. If the value is Default, then the value of real_prec is used.
round

There are five rounding modes availble to mpfr types:

RoundAwayZero
The result is rounded away from 0.0.
RoundDown
The result is rounded towards -Infinity.
RoundToNearest
Round to the nearest value; ties are rounded to an even value.
RoundToZero
The result is rounded towards 0.0.
RoundUp
The result is rounded towards +Infinity.
real_round
This attribute controls the rounding mode for the real part of an mpc result. If the value is Default, then the value of the round attribute is used. Note: RoundAwayZero is not a valid rounding mode for mpc.
imag_round
This attribute controls the rounding mode for the imaginary part of an mpc result. If the value is Default, then the value of the real_round attribute is used. Note: RoundAwayZero is not a valid rounding mode for mpc.
emax
This attribute controls the maximum allowed exponent of an mpfr result. The maximum exponent is platform dependent and can be retrieved with get_emax_max().
emin
This attribute controls the minimum allowed exponent of an mpfr result. The minimum exponent is platform dependent and can be retrieved with get_emin_min().

Note

It is possible to change the values of emin/emax such that previous mpfr values are no longer valid numbers but should either underflow to +/-0.0 or overflow to +/-Infinity. To raise an exception if this occurs, see trap_expbound.

subnormalize
The usual IEEE-754 floating point representation supports gradual underflow when the minimum exponent is reached. The MFPR library does not enable gradual underflow by default but it can be enabled to precisely mimic the results of IEEE-754 floating point operations.
trap_underflow
If set to False, a result that is smaller than the smallest possible mpfr given the current exponent range will be replaced by +/-0.0. If set to True, an UnderflowResultError exception is raised.
underflow
This flag is not user controllable. It is automatically set if a result underflowed to +/-0.0 and trap_underflow is False.
trap_overflow
If set to False, a result that is larger than the largest possible mpfr given the current exponent range will be replaced by +/-Infinity. If set to True, an OverflowResultError exception is raised.
overflow
This flag is not user controllable. It is automatically set if a result overflowed to +/-Infinity and trap_overflow is False.
trap_inexact
This attribute controls whether or not an InexactResultError exception is raised if an inexact result is returned. To check if the result is greater or less than the exact result, check the rc attribute of the mpfr result.
inexact
This flag is not user controllable. It is automatically set if an inexact result is returned.
trap_invalid

This attribute controls whether or not an InvalidOperationError exception is raised if a numerical result is not defined. A special NaN (Not-A-Number) value will be returned if an exception is not raised. The InvalidOperationError is a sub-class of Python’s ValueError.

For example, gmpy2.sqrt(-2) will normally return mpfr(‘nan’). However, if allow_complex is set to True, then an mpc result will be returned.

invalid
This flag is not user controllable. It is automatically set if an invalid (Not-A-Number) result is returned.
trap_erange

This attribute controls whether or not a RangeError exception is raised when certain operations are performed on NaN and/or Infinity values. Setting trap_erange to True can be used to raise an exception if comparisons are attempted with a NaN.

>>> gmpy2.set_context(gmpy2.context())
>>> mpfr('nan') == mpfr('nan')
False
>>> gmpy2.get_context().trap_erange=True
>>> mpfr('nan') == mpfr('nan')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
gmpy2.RangeError: comparison with NaN
>>>
erange
This flag is not user controllable. It is automatically set if an erange error occurred.
trap_divzero
This attribute controls whether or not a DivisionByZeroError exception is raised if division by 0 occurs. The DivisionByZeroError is a sub-class of Python’s ZeroDivisionError.
divzero
This flag is not user controllable. It is automatically set if a division by zero occurred and NaN result was returned.
trap_expbound
This attribute controls whether or not an ExponentOutOfBoundsError exception is raised if exponents in an operand are outside the current emin/emax limits.
allow_complex
This attribute controls whether or not an mpc result can be returned if an mpfr result would normally not be possible.

Context Methods

clear_flags()
Clear the underflow, overflow, inexact, invalid, erange, and divzero flags.
copy()
Return a copy of the context.

Contexts and the with statement

Contexts can also be used in conjunction with Python’s with ... statement to temporarily change the context settings for a block of code and then restore the original settings when the block of code exits.

gmpy2.local_context() first save the current context and then creates a new context based on a context passed as the first argument, or the current context if no context is passed. The new context is modified if any optional keyword arguments are given. The orginal active context is restored when the block completes.

In the following example, the current context is saved by gmpy2.local_context() and then the block begins with a copy of the default context and the precision set to 100. When the block is finished, the original context is restored.

>>> with gmpy2.local_context(gmpy2.context(), precision=100) as ctx:
...   print(gmpy2.sqrt(2))
...   ctx.precision += 100
...   print(gmpy2.sqrt(2))
...
1.4142135623730950488016887242092
1.4142135623730950488016887242096980785696718753769480731766796
>>>

A context object can also be used directly to create a context manager block. However, instead of restoring the context to the active context when the with ... statement is executed, the restored context is the context used before any keyword argument modifications.

The code:

::
with gmpy2.ieee(64) as ctx:

is equivalent to:

::
gmpy2.set_context(gmpy2.ieee(64)) with gmpy2.local_context() as ctx:

Contexts that implement the standard single, double, and quadruple precision floating point types can be created using ieee().

mpfr Methods

as_integer_ratio()
Returns a 2-tuple containing the numerator and denominator after converting the mpfr object into the exact rational equivalent. The return 2-tuple is equivalent to Python’s as_integer_ratio() method of built-in float objects.
as_mantissa_exp()
Returns a 2-tuple containing the mantissa and exponent.
as_simple_fraction()
Returns an mpq containing the simpliest rational value that approximates the mpfr value with an error less than 1/(2**precision).
conjugate()
Returns the complex conjugate. For mpfr objects, returns a copy of the original object.
digits()
Returns a 3-tuple containing the mantissa, the exponent, and the number of bits of precision. The mantissa is represented as a string in the specified base with up to ‘prec’ digits. If ‘prec’ is 0, as many digits that are available are returned. No more digits than available given x’s precision are returned. ‘base’ must be between 2 and 62, inclusive.
is_integer()
Returns True if the mpfr object is an integer.

mpfr Attributes

imag
Returns the imaginary component. For mpfr objects, returns 0.
precision
Returns the precision of the mpfr object.
rc
The result code (also known as ternary value in the MPFR documentation) is 0 if the value of the mpfr object is exactly equal to the exact, infinite precision value. If the result code is 1, then the value of the mpfr object is greater than the exact value. If the result code is -1, then the value of the mpfr object is less than the exact, infinite precision value.
real
Returns the real component. For mpfr objects, returns a copy of the original object.

mpfr Functions

acos(...)
acos(x) returns the arc-cosine of x. x is measured in radians. If context.allow_complex is True, then an mpc result will be returned for abs(x) > 1.
acosh(...)
acosh(x) returns the inverse hyperbolic cosine of x.
add(...)
add(x, y) returns x + y. The type of the result is based on the types of the arguments.
agm(...)
agm(x, y) returns the arithmetic-geometric mean of x and y.
ai(...)
ai(x) returns the Airy function of x.
asin(...)
asin(x) returns the arc-sine of x. x is measured in radians. If context.allow_complex is True, then an mpc result will be returned for abs(x) > 1.
asinh(...)
asinh(x) return the inverse hyperbolic sine of x.
atan(...)
atan(x) returns the arc-tangent of x. x is measured in radians.
atan2(...)
atan2(y, x) returns the arc-tangent of (y/x).
atanh(...)
atanh(x) returns the inverse hyperbolic tangent of x. If context.allow_complex is True, then an mpc result will be returned for abs(x) > 1.
cbrt(...)
cbrt(x) returns the cube root of x.
ceil(...)
ceil(x) returns the ‘mpfr’ that is the smallest integer >= x.
check_range(...)
check_range(x) return a new ‘mpfr’ with exponent that lies within the current range of emin and emax.
const_catalan(...)
const_catalan([precision=0]) returns the catalan constant using the specified precision. If no precision is specified, the default precision is used.
const_euler(...)
const_euler([precision=0]) returns the euler constant using the specified precision. If no precision is specified, the default precision is used.
const_log2(...)
const_log2([precision=0]) returns the log2 constant using the specified precision. If no precision is specified, the default precision is used.
const_pi(...)
const_pi([precision=0]) returns the constant pi using the specified precision. If no precision is specified, the default precision is used.
context(...)
context() returns a new context manager controlling MPFR and MPC arithmetic.
cos(...)
cos(x) seturns the cosine of x. x is measured in radians.
cosh(...)
cosh(x) returns the hyperbolic cosine of x.
cot(...)
cot(x) returns the cotangent of x. x is measured in radians.
coth(...)
coth(x) returns the hyperbolic cotangent of x.
csc(...)
csc(x) returns the cosecant of x. x is measured in radians.
csch(...)
csch(x) returns the hyperbolic cosecant of x.
degrees(...)
degrees(x) converts an angle measurement x from radians to degrees.
digamma(...)
digamma(x) returns the digamma of x.
div(...)
div(x, y) returns x / y. The type of the result is based on the types of the arguments.
div_2exp(...)
div_2exp(x, n) returns an ‘mpfr’ or ‘mpc’ divided by 2**n.
eint(...)
eint(x) returns the exponential integral of x.
erf(...)
erf(x) returns the error function of x.
erfc(...)
erfc(x) returns the complementary error function of x.
exp(...)
exp(x) returns e**x.
exp10(...)
exp10(x) returns 10**x.
exp2(...)
exp2(x) returns 2**x.
expm1(...)
expm1(x) returns e**x - 1. expm1() is more accurate than exp(x) - 1 when x is small.
f2q(...)
f2q(x[,err]) returns the simplest mpq approximating x to within relative error err. Default is the precision of x. Uses Stern-Brocot tree to find the simplist approximation. An mpz is returned if the the denominator is 1. If err<0, error sought is 2.0 ** err.
factorial(...)

factorial(n) returns the floating-point approximation to the factorial of n.

See fac(n) to get the exact integer result.

floor(...)
floor(x) returns the ‘mpfr’ that is the smallest integer <= x.
fma(...)
fma(x, y, z) returns correctly rounded result of (x * y) + z.
fmod(...)
fmod(x, y) returns x - n*y where n is the integer quotient of x/y, rounded to 0.
fms(...)
fms(x, y, z) returns correctly rounded result of (x * y) - z.
frac(...)
frac(x) returns the fractional part of x.
frexp(...)
frexp(x) returns a tuple containing the exponent and mantissa of x.
fsum(...)
fsum(iterable) returns the accurate sum of the values in the iterable.
gamma(...)
gamma(x) returns the gamma of x.
get_exp(...)
get_exp(mpfr) returns the exponent of an mpfr. Returns 0 for NaN or Infinity and sets the erange flag and will raise an exception if trap_erange is set.
hypot(...)
hypot(y, x) returns square root of (x**2 + y**2).
ieee(...)
ieee(bitwidth) returns a context with settings for 32-bit (aka single), 64-bit (aka double), or 128-bit (aka quadruple) precision floating point types.
inf(...)
inf(n) returns an mpfr initialized to Infinity with the same sign as n. If n is not given, +Infinity is returned.
is_finite(...)
is_finite(x) returns True if x is an actual number (i.e. not NaN or Infinity).
is_inf(...)

is_inf(x) returns True if x is Infinity or -Infinity.

Note

is_inf() is deprecated; please use if_infinite().

is_infinite(...)
is_infinite(x) returns True if x Infinity or -Infinity.
is_nan(...)
is_nan(x) returns True if x is NaN (Not-A-Number).
is_number(...)

is_number(x) returns True if x is an actual number (i.e. not NaN or Infinity).

Note

is_number() is deprecated; please use is_finite().

is_regular(...)
is_regular(x) returns True if x is not zero, NaN, or Infinity.
is_signed(...)
is_signed(x) returns True if the sign bit of x is set.
is_unordered(...)
is_unordered(x,y) returns True if either x and/or y is NaN.
is_zero(...)
is_zero(x) returns True if x is zero.
j0(...)
j0(x) returns the Bessel function of the first kind of order 0 of x.
j1(...)
j1(x) returns the Bessel function of the first kind of order 1 of x.
jn(...)
jn(x,n) returns the Bessel function of the first kind of order n of x.
lgamma(...)
lgamma(x) returns a tuple containing the logarithm of the absolute value of gamma(x) and the sign of gamma(x)
li2(...)
li2(x) returns the real part of dilogarithm of x.
lngamma(...)
lngamma(x) returns the logarithm of gamma(x).
log(...)
log(x) returns the natural logarithm of x.
log10(...)
log10(x) returns the base-10 logarithm of x.
log1p(...)
log1p(x) returns the natural logarithm of (1+x).
log2(...)
log2(x) returns the base-2 logarithm of x.
max2(...)
max2(x, y) returns the maximum of x and y. The result may be rounded to match the current context. Use the builtin max() to get an exact copy of the largest object without any rounding.
min2(...)
min2(x, y) returns the minimum of x and y. The result may be rounded to match the current context. Use the builtin min() to get an exact copy of the smallest object without any rounding.
modf(...)
modf(x) returns a tuple containing the integer and fractional portions of x.
mpfr(...)

mpfr() returns and mpfr object set to 0.0.

mpfr(n[, precison=0]) returns an mpfr object after converting a numeric value n. If no precision, or a precision of 0, is specified; the precision is taken from the current context.

mpfr(s[, precision=0[, [base=0]]) returns an mpfr object after converting a string ‘s’ made up of digits in the given base, possibly with fractional part (with period as a separator) and/or exponent (with exponent marker ‘e’ for base<=10, else ‘@’). If no precision, or a precision of 0, is specified; the precison is taken from the current context. The base of the string representation must be 0 or in the interval 2 ... 62. If the base is 0, the leading digits of the string are used to identify the base: 0b implies base=2, 0x implies base=16, otherwise base=10 is assumed.

mpfr_from_old_binary(...)
mpfr_from_old_binary(string) returns an mpfr from a GMPY 1.x binary mpf format. Please use to_binary()/from_binary() to convert GMPY2 objects to or from a binary format.
mpfr_grandom(...)
mpfr_grandom(random_state) returns two random numbers with gaussian distribution. The parameter random_state must be created by random_state() first.
mpfr_random(...)
mpfr_random(random_state) returns a uniformly distributed number between [0,1]. The parameter random_state must be created by random_state() first.
mul(...)
mul(x, y) returns x * y. The type of the result is based on the types of the arguments.
mul_2exp(...)
mul_2exp(x, n) returns ‘mpfr’ or ‘mpc’ multiplied by 2**n.
nan(...)
nan() returns an ‘mpfr’ initialized to NaN (Not-A-Number).
next_above(...)
next_above(x) returns the next ‘mpfr’ from x toward +Infinity.
next_below(...)
next_below(x) returns the next ‘mpfr’ from x toward -Infinity.
radians(...)
radians(x) converts an angle measurement x from degrees to radians.
rec_sqrt(...)
rec_sqrt(x) returns the reciprocal of the square root of x.
reldiff(...)
reldiff(x, y) returns the relative difference between x and y. Result is equal to abs(x-y)/x.
remainder(...)
remainder(x, y) returns x - n*y where n is the integer quotient of x/y, rounded to the nearest integer and ties rounded to even.
remquo(...)
remquo(x, y) returns a tuple containing the remainder(x,y) and the low bits of the quotient.
rint(...)
rint(x) returns x rounded to the nearest integer using the current rounding mode.
rint_ceil(...)
rint_ceil(x) returns x rounded to the nearest integer by first rounding to the next higher or equal integer and then, if needed, using the current rounding mode.
rint_floor(...)
rint_floor(x) returns x rounded to the nearest integer by first rounding to the next lower or equal integer and then, if needed, using the current rounding mode.
rint_round(...)
rint_round(x) returns x rounded to the nearest integer by first rounding to the nearest integer (ties away from 0) and then, if needed, using the current rounding mode.
rint_trunc(...)
rint_trunc(x) returns x rounded to the nearest integer by first rounding towards zero and then, if needed, using the current rounding mode.
root(...)
root(x, n) returns n-th root of x. The result always an mpfr.
round2(...)
round2(x[, n]) returns x rounded to n bits. Uses default precision if n is not specified. See round_away() to access the mpfr_round() function. Use the builtin round() to round x to n decimal digits.
round_away(...)
round_away(x) returns an mpfr by rounding x the nearest integer, with ties rounded away from 0.
sec(...)
sec(x) returns the secant of x. x is measured in radians.
sech(...)
sech(x) returns the hyperbolic secant of x.
set_exp(...)
set_exp(x, n) sets the exponent of a given mpfr to n. If n is outside the range of valid exponents, set_exp() will set the erange flag and either return the original value or raise an exception if trap_erange is set.
set_sign(...)
set_sign(x, bool) returns a copy of x with it’s sign bit set if bool evaluates to True.
sign(...)
sign(x) returns -1 if x < 0, 0 if x == 0, or +1 if x >0.
sin(...)
sin(x) returns the sine of x. x is measured in radians.
sin_cos(...)
sin_cos(x) returns a tuple containing the sine and cosine of x. x is measured in radians.
sinh(...)
sinh(x) returns the hyberbolic sine of x.
sinh_cosh(...)
sinh_cosh(x) returns a tuple containing the hyperbolic sine and cosine of x.
sqrt(...)
sqrt(x) returns the square root of x. If x is integer, rational, or real, then an mpfr will be returned. If x is complex, then an mpc will be returned. If context.allow_complex is True, negative values of x will return an mpc.
square(...)
square(x) returns x * x. The type of the result is based on the types of the arguments.
sub(...)
sub(x, y) returns x - y. The type of the result is based on the types of the arguments.
tan(...)
tan(x) returns the tangent of x. x is measured in radians.
tanh(...)
tanh(x) returns the hyperbolic tangent of x.
trunc(...)
trunc(x) returns an ‘mpfr’ that is x truncated towards 0. Same as x.floor() if x>=0 or x.ceil() if x<0.
y0(...)
y0(x) returns the Bessel function of the second kind of order 0 of x.
y1(...)
y1(x) returns the Bessel function of the second kind of order 1 of x.
yn(...)
yn(x,n) returns the Bessel function of the second kind of order n of x.
zero(...)
zero(n) returns an mpfr inialized to 0.0 with the same sign as n. If n is not given, +0.0 is returned.
zeta(...)
zeta(x) returns the Riemann zeta of x.

mpfr Formatting

The mpfr type supports the __format__() special method to allow custom output formatting.

__format__(...)

x.__format__(fmt) returns a Python string by formatting ‘x’ using the format string ‘fmt’. A valid format string consists of:

optional alignment code:
‘<’ -> left shifted in field
‘>’ -> right shifted in field
‘^’ -> centered in field
optional leading sign code
‘+’ -> always display leading sign
‘-‘ -> only display minus for negative values
‘ ‘ -> minus for negative values, space for positive values
optional width.precision
optional rounding mode:
‘U’ -> round toward plus infinity
‘D’ -> round toward minus infinity
‘Y’ -> round away from zero
‘Z’ -> round toward zero
‘N’ -> round to nearest
optional conversion code:
‘a’,’A’ -> hex format
‘b’ -> binary format
‘e’,’E’ -> scientific format
‘f’,’F’ -> fixed point format
‘g’,’G’ -> fixed or scientific format

Note

The formatting codes must be specified in the order shown above.

>>> import gmpy2
>>> from gmpy2 import mpfr
>>> a=mpfr("1.23456")
>>> "{0:15.3f}".format(a)
'          1.235'
>>> "{0:15.3Uf}".format(a)
'          1.235'
>>> "{0:15.3Df}".format(a)
'          1.234'
>>> "{0:.3Df}".format(a)
'1.234'
>>> "{0:+.3Df}".format(a)
'+1.234'

Project Versions

Table Of Contents

Previous topic

Multiple-precision Rationals

Next topic

Multiple-precision Complex

This Page