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eric-wiesereric-wieser
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ENH: Implement np.floating.as_integer_ratio
This matches the builtin `float.as_integer_ratio` and (in recent python versions) `int.as_integer_ratio`.
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‎doc/release/1.17.0-notes.rst

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@@ -129,6 +129,12 @@ New mode "empty" for ``np.pad``
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This mode pads an array to a desired shape without initializing the new
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entries.
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Floating point scalars implement ``as_integer_ratio`` to match the builtin float
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--------------------------------------------------------------------------------
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This returns a (numerator, denominator) pair, which can be used to construct a
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`fractions.Fraction`.
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Improvements
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============
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‎numpy/core/_add_newdocs.py

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@@ -6903,3 +6903,21 @@ def add_newdoc_for_scalar_type(obj, fixed_aliases, doc):
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"""
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Any Python object.
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""")
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# TODO: work out how to put this on the base class, np.floating
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for float_name in ('half', 'single', 'double', 'longdouble'):
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add_newdoc('numpy.core.numerictypes', float_name, ('as_integer_ratio',
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"""
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{ftype}.as_integer_ratio() -> (int, int)
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Return a pair of integers, whose ratio is exactly equal to the original
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floating point number, and with a positive denominator.
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Raise OverflowError on infinities and a ValueError on NaNs.
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>>> np.{ftype}(10.0).as_integer_ratio()
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(10, 1)
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>>> np.{ftype}(0.0).as_integer_ratio()
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(0, 1)
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>>> np.{ftype}(-.25).as_integer_ratio()
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(-1, 4)
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""".format(ftype=float_name)))

‎numpy/core/src/multiarray/scalartypes.c.src

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@@ -1993,6 +1993,92 @@ static PyObject *
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}
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/**end repeat**/
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/**begin repeat
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* #name = half, float, double, longdouble#
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* #Name = Half, Float, Double, LongDouble#
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* #is_half = 1,0,0,0#
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* #c = f, f, , l#
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* #convert = PyLong_FromDouble, PyLong_FromDouble, PyLong_FromDouble,
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* npy_longdouble_to_PyLong#
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* #
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*/
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/* Heavily copied from the builtin float.as_integer_ratio */
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static PyObject *
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@name@_as_integer_ratio(PyObject *self)
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{
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#if @is_half@
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npy_double val = npy_half_to_double(PyArrayScalar_VAL(self, @Name@));
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npy_double frac;
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#else
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npy_@name@ val = PyArrayScalar_VAL(self, @Name@);
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npy_@name@ frac;
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#endif
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int exponent;
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int i;
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PyObject *py_exponent = NULL;
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PyObject *numerator = NULL;
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PyObject *denominator = NULL;
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PyObject *result_pair = NULL;
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PyNumberMethods *long_methods = PyLong_Type.tp_as_number;
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if (npy_isnan(val)) {
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PyErr_SetString(PyExc_ValueError,
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"cannot convert NaN to integer ratio");
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return NULL;
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}
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if (!npy_isfinite(val)) {
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PyErr_SetString(PyExc_OverflowError,
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"cannot convert Infinity to integer ratio");
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return NULL;
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}
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frac = npy_frexp@c@(val, &exponent); /* val == frac * 2**exponent exactly */
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/* This relies on the floating point type being base 2 to converge */
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for (i = 0; frac != npy_floor@c@(frac); i++) {
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frac *= 2.0;
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exponent--;
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}
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/* self == frac * 2**exponent exactly and frac is integral. */
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numerator = @convert@(frac);
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if (numerator == NULL)
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goto error;
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denominator = PyLong_FromLong(1);
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if (denominator == NULL)
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goto error;
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py_exponent = PyLong_FromLong(exponent < 0 ? -exponent : exponent);
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if (py_exponent == NULL)
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goto error;
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/* fold in 2**exponent */
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if (exponent > 0) {
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PyObject *temp = long_methods->nb_lshift(numerator, py_exponent);
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if (temp == NULL)
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goto error;
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Py_DECREF(numerator);
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numerator = temp;
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}
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else {
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PyObject *temp = long_methods->nb_lshift(denominator, py_exponent);
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if (temp == NULL)
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goto error;
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Py_DECREF(denominator);
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denominator = temp;
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}
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result_pair = PyTuple_Pack(2, numerator, denominator);
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error:
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Py_XDECREF(py_exponent);
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Py_XDECREF(denominator);
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Py_XDECREF(numerator);
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return result_pair;
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}
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/**end repeat**/
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/*
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* need to fill in doc-strings for these methods on import -- copy from
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* array docstrings
@@ -2256,6 +2342,17 @@ static PyMethodDef @name@type_methods[] = {
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};
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/**end repeat**/
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/**begin repeat
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* #name = half,float,double,longdouble#
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*/
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static PyMethodDef @name@type_methods[] = {
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{"as_integer_ratio",
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(PyCFunction)@name@_as_integer_ratio,
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METH_NOARGS, NULL},
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{NULL, NULL, 0, NULL}
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};
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/**end repeat**/
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/************* As_mapping functions for void array scalar ************/
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static Py_ssize_t
@@ -4311,6 +4408,15 @@ initialize_numeric_types(void)
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/**end repeat**/
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/**begin repeat
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* #name = half, float, double, longdouble#
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* #Name = Half, Float, Double, LongDouble#
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*/
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Py@Name@ArrType_Type.tp_methods = @name@type_methods;
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/**end repeat**/
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#if (NPY_SIZEOF_INT != NPY_SIZEOF_LONG) || defined(NPY_PY3K)
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/* We won't be inheriting from Python Int type. */
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PyIntArrType_Type.tp_hash = int_arrtype_hash;

‎numpy/core/tests/test_scalar_methods.py

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"""
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Test the scalar constructors, which also do type-coercion
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"""
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from __future__ import division, absolute_import, print_function
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import fractions
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import numpy as np
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from numpy.testing import (
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run_module_suite,
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assert_equal, assert_almost_equal, assert_raises, assert_warns,
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dec
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)
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float_types = [np.half, np.single, np.double, np.longdouble]
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def test_float_as_integer_ratio():
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# derived from the cpython test "test_floatasratio"
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for ftype in float_types:
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for f, ratio in [
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(0.875, (7, 8)),
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(-0.875, (-7, 8)),
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(0.0, (0, 1)),
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(11.5, (23, 2)),
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]:
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assert_equal(ftype(f).as_integer_ratio(), ratio)
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rstate = np.random.RandomState(0)
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fi = np.finfo(ftype)
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for i in range(1000):
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exp = rstate.randint(fi.minexp, fi.maxexp - 1)
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frac = rstate.rand()
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f = np.ldexp(frac, exp, dtype=ftype)
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n, d = f.as_integer_ratio()
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try:
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dn = np.longdouble(str(n))
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df = np.longdouble(str(d))
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except (OverflowError, RuntimeWarning):
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# the values may not fit in any float type
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continue
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assert_equal(
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dn / df, f,
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"{}/{} (dtype={})".format(n, d, ftype.__name__))
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R = fractions.Fraction
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assert_equal(R(0, 1),
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R(*ftype(0.0).as_integer_ratio()))
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assert_equal(R(5, 2),
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R(*ftype(2.5).as_integer_ratio()))
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assert_equal(R(1, 2),
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R(*ftype(0.5).as_integer_ratio()))
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assert_equal(R(-2100, 1),
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R(*ftype(-2100.0).as_integer_ratio()))
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assert_raises(OverflowError, ftype('inf').as_integer_ratio)
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assert_raises(OverflowError, ftype('-inf').as_integer_ratio)
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assert_raises(ValueError, ftype('nan').as_integer_ratio)
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assert_equal(R(1075, 512),
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R(*np.half(2.1).as_integer_ratio()))
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assert_equal(R(-1075, 512),
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R(*np.half(-2.1).as_integer_ratio()))
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assert_equal(R(4404019, 2097152),
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R(*np.single(2.1).as_integer_ratio()))
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assert_equal(R(-4404019, 2097152),
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R(*np.single(-2.1).as_integer_ratio()))
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assert_equal(R(4728779608739021, 2251799813685248),
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R(*np.double(2.1).as_integer_ratio()))
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assert_equal(R(-4728779608739021, 2251799813685248),
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R(*np.double(-2.1).as_integer_ratio()))
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# longdouble is platform depedent
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if __name__ == "__main__":
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run_module_suite()

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