From 4002713f7e17959359f2066c478efa620ffd9e6b Mon Sep 17 00:00:00 2001
From: AlexAndorra <andorra.alexandre@gmail.com>
Date: Mon, 11 May 2020 18:14:46 +0200
Subject: [PATCH 1/3] Set start method to forkserver for MacOS

---
 pymc3/__init__.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/pymc3/__init__.py b/pymc3/__init__.py
index 624e9b9ab8..cb51ff4c9d 100644
--- a/pymc3/__init__.py
+++ b/pymc3/__init__.py
@@ -16,6 +16,8 @@
 __version__ = "3.8"
 
 import logging
+import multiprocessing as mp
+import platform
 
 _log = logging.getLogger("pymc3")
 
@@ -25,10 +27,13 @@
         handler = logging.StreamHandler()
         _log.addHandler(handler)
 
+sys = platform.system()
+if sys == "Darwin":
+    _ = mp.get_context("forkserver")
+
 
 def __set_compiler_flags():
     # Workarounds for Theano compiler problems on various platforms
-    import platform
     import theano
 
     system = platform.system()

From 1945485e187e30d7a045cb91a66c8ed1534ac046 Mon Sep 17 00:00:00 2001
From: AlexAndorra <andorra.alexandre@gmail.com>
Date: Mon, 11 May 2020 18:51:06 +0200
Subject: [PATCH 2/3] Polished up changes

---
 pymc3/__init__.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pymc3/__init__.py b/pymc3/__init__.py
index cb51ff4c9d..83f7c745c9 100644
--- a/pymc3/__init__.py
+++ b/pymc3/__init__.py
@@ -27,9 +27,11 @@
         handler = logging.StreamHandler()
         _log.addHandler(handler)
 
+# Set start method to forkserver for MacOS to enable multiprocessing
+# Closes issue https://github.com/pymc-devs/pymc3/issues/3849
 sys = platform.system()
 if sys == "Darwin":
-    _ = mp.get_context("forkserver")
+    new_context = mp.get_context("forkserver")
 
 
 def __set_compiler_flags():

From a5c1ad3b81f6975f1f8945ff022367969f59d9c6 Mon Sep 17 00:00:00 2001
From: AlexAndorra <andorra.alexandre@gmail.com>
Date: Mon, 11 May 2020 19:17:46 +0200
Subject: [PATCH 3/3] Added release note

---
 RELEASE-NOTES.md | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/RELEASE-NOTES.md b/RELEASE-NOTES.md
index d141236602..d593ad2141 100644
--- a/RELEASE-NOTES.md
+++ b/RELEASE-NOTES.md
@@ -21,9 +21,10 @@
 - `pm.sample` now takes 1000 draws and 1000 tuning samples by default, instead of 500 previously (see [#3855](https://github.com/pymc-devs/pymc3/pull/3855)).
 - Moved argument division out of `NegativeBinomial` `random` method. Fixes [#3864](https://github.com/pymc-devs/pymc3/issues/3864) in the style of [#3509](https://github.com/pymc-devs/pymc3/pull/3509).
 - The Dirichlet distribution now raises a ValueError when it's initialized with <= 0 values (see [#3853](https://github.com/pymc-devs/pymc3/pull/3853)).
-- Dtype bugfix in `MvNormal` and `MvStudentT` (see [3836](https://github.com/pymc-devs/pymc3/pull/3836))
+- Dtype bugfix in `MvNormal` and `MvStudentT` (see [3836](https://github.com/pymc-devs/pymc3/pull/3836)).
 - End of sampling report now uses `arviz.InferenceData` internally and avoids storing
-  pointwise log likelihood (see [#3883](https://github.com/pymc-devs/pymc3/pull/3883))
+  pointwise log likelihood (see [#3883](https://github.com/pymc-devs/pymc3/pull/3883)).
+- The multiprocessing start method on MacOS is now set to "forkserver", to avoid crashes (see issue [#3849](https://github.com/pymc-devs/pymc3/issues/3849), solved by [#3919](https://github.com/pymc-devs/pymc3/pull/3919)).
 
 ### Deprecations
 - Remove `sample_ppc` and `sample_ppc_w` that were deprecated in 3.6.