Remove float128 dtype

Backport of #4514.

Removes float128 dtype which does not exist on Windows and newer OSX versions and furthermore does not to be properly supported even if it does exist.

Author: twiecki

Diff for: RELEASE-NOTES.md

@@ -5,8 +5,9 @@
 + A deprecation warning from the `semver` package we use for checking backend compatibility was dealt with (see [#4547](https://github.com/pymc-devs/pymc3/pull/4547)).
 + `theano.printing.pydotprint` is now hotfixed upon import (see [#4594](https://github.com/pymc-devs/pymc3/pull/4594)).
 + Fix bug in the computation of the log pseudolikelihood values (SMC-ABC). (see [#4672](https://github.com/pymc-devs/pymc3/pull/4672)).
-+ Fix `LKJCorr.random` method to work with `pm.sample_prior_predictive`. (see [#4780](https://github.com/pymc-devs/pymc3/pull/4780))
++ Fix `LKJCorr.random` method to work with `pm.sample_prior_predictive`. (see [#4780](https://github.com/pymc-devs/pymc3/pull/4780)).
 + Enable documentation generation via ReadTheDocs for upcoming v3 releases. (see [#4805](https://github.com/pymc-devs/pymc3/pull/4805)).
++ Remove `float128` dtype support (see [#4834](https://github.com/pymc-devs/pymc3/pull/4834)).
 
 ### New Features
 + Generalized BART, bounded distributions like Binomial and Poisson can now be used as likelihoods (see [#4675](https://github.com/pymc-devs/pymc3/pull/4675), [#4709](https://github.com/pymc-devs/pymc3/pull/4709) and

Diff for: pymc3/distributions/dist_math.py

@@ -1,4 +1,4 @@
-#   Copyright 2020 The PyMC Developers
+#   Copyright 2021 The PyMC Developers
 #
 #   Licensed under the Apache License, Version 2.0 (the "License");
 #   you may not use this file except in compliance with the License.
@@ -17,8 +17,6 @@
 
 @author: johnsalvatier
 """
-import platform
-
 import numpy as np
 import scipy.linalg
 import scipy.stats
@@ -44,11 +42,6 @@
     dtype: (np.nextafter(0, 1, dtype=dtype), np.nextafter(1, 0, dtype=dtype))
     for dtype in ["float16", "float32", "float64"]
 }
-if platform.system() in ["Linux", "Darwin"]:
-    _beta_clip_values["float128"] = (
-        np.nextafter(0, 1, dtype="float128"),
-        np.nextafter(1, 0, dtype="float128"),
-    )
 
 
 def bound(logp, *conditions, **kwargs):

Diff for: pymc3/tests/test_dist_math.py

@@ -1,4 +1,4 @@
-#   Copyright 2020 The PyMC Developers
+#   Copyright 2021 The PyMC Developers
 #
 #   Licensed under the Apache License, Version 2.0 (the "License");
 #   you may not use this file except in compliance with the License.
@@ -10,9 +10,6 @@
 #   distributed under the License is distributed on an "AS IS" BASIS,
 #   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 #   See the License for the specific language governing permissions and
-#   limitations under the License.
-import sys
-
 import numpy as np
 import numpy.testing as npt
 import pytest
@@ -237,12 +234,7 @@ def test_grad(self):
         verify_grad(i0e, [[[0.5, -2.0]]])
 
 
-@pytest.mark.parametrize(
-    "dtype",
-    ["float16", "float32", "float64", "float128"]
-    if sys.platform != "win32"
-    else ["float16", "float32", "float64"],
-)
+@pytest.mark.parametrize("dtype", ["float16", "float32", "float64"])
 def test_clipped_beta_rvs(dtype):
     # Verify that the samples drawn from the beta distribution are never
     # equal to zero or one (issue #3898)