From d6afbc3cafac255f55c46d1f3c21858672f86191 Mon Sep 17 00:00:00 2001
From: Wim Pomp <w.pomp@nki.nl>
Date: Sun, 20 Oct 2024 13:10:49 +0200
Subject: [PATCH] - add PoolSingleton to __init__ - update readme

---
 README.md          | 21 +++++++++++++++++----
 parfor/__init__.py | 23 +++++++++--------------
 pyproject.toml     |  2 +-
 3 files changed, 27 insertions(+), 19 deletions(-)

diff --git a/README.md b/README.md
index e5ef78a..d679271 100644
--- a/README.md
+++ b/README.md
@@ -12,8 +12,13 @@ Tested on linux, Windows and OSX with python 3.10 and 3.12.
 - Easy to use
 - Using dill instead of pickle: a lot more objects can be used when parallelizing
 - Progress bars are built-in
+- Automatically use multithreading instead of multiprocessing when the GIL is disabled
 
 ## How it works
+This depends on whether the GIL is currently disabled or not. Disabling the GIL in Python is currently an experimental
+feature in Python3.13, and not the standard.
+
+### Python with GIL enabled
 The work you want parfor to do is divided over a number of processes. These processes are started by parfor and put
 together in a pool. This pool is reused when you want parfor to do more work, or shut down when no new work arrives
 within 10 minutes.
@@ -24,6 +29,12 @@ worker is requesting it. The manager deletes objects automatically when they're
 
 When the work is done the result is sent back for collection in the main process.
 
+### Python with GIL disabled
+The work you want parfor to do is given to a new thread. These threads are started by parfor and put together in a pool.
+The threads and pool are not reused and closed automatically when done.
+
+When the work is done a message is sent to the main thread to update the status of the pool.
+
 ## Installation
 `pip install parfor`
 
@@ -35,12 +46,14 @@ an iterator.
 tqdm, dill
 
 ## Limitations
-Objects passed to the pool need to be dillable (dill needs to serialize them). Generators and SwigPyObjects are examples
-of objects that cannot be used. They can be used however, for the iterator argument when using parfor, but its
-iterations need to be dillable. You might be able to make objects dillable anyhow using `dill.register` or with
-`__reduce__`, `__getstate__`, etc.
+If you're using Python with the GIL enabaled, then objects passed to the pool need to be dillable (dill needs to
+serialize them). Generators and SwigPyObjects are examples of objects that cannot be used. They can be used however, for
+the iterator argument when using parfor, but its iterations need to be dillable. You might be able to make objects
+dillable anyhow using `dill.register` or with `__reduce__`, `__getstate__`, etc.
 
 ## Arguments
+To functions `parfor.parfor`, `parfor.pmap` and `parfor.gmap`.
+
 ### Required:
     fun:      function taking arguments: iteration from  iterable, other arguments defined in args & kwargs
     iterable: iterable or iterator from which an item is given to fun as a first argument
diff --git a/parfor/__init__.py b/parfor/__init__.py
index a9c7476..e8bde20 100644
--- a/parfor/__init__.py
+++ b/parfor/__init__.py
@@ -19,23 +19,18 @@ Result = TypeVar('Result')
 Iteration = TypeVar('Iteration')
 
 
+def select():
+    return nogil if hasattr(sys, '_is_gil_enabled') and not sys._is_gil_enabled() else gil  # noqa
+
+
 class ParPool:
     def __new__(cls, *args, **kwargs):
-        try:
-            if not sys._is_gil_enabled():  # noqa
-                return nogil.ParPool(*args, **kwargs)
-        except AttributeError:
-            pass
-        return gil.ParPool(*args, **kwargs)
+        return select().ParPool(*args, **kwargs)
 
 
-def nested():
-    try:
-        if not sys._is_gil_enabled():  # noqa
-            return nogil.Worker.nested
-    except AttributeError:
-        pass
-    return gil.Worker.nested
+class PoolSingleton:
+    def __new__(cls, *args, **kwargs):
+        return select().PoolSingleton(*args, **kwargs)
 
 
 class Chunks(Iterable):
@@ -222,7 +217,7 @@ def gmap(fun: Callable[[Iteration, Any, ...], Result], iterable: Iterable[Iterat
         bar_kwargs['desc'] = desc
     if 'disable' not in bar_kwargs:
         bar_kwargs['disable'] = not bar
-    if serial is True or (serial is None and len(iterable) < min(cpu_count, 4)) or nested():  # serial case
+    if serial is True or (serial is None and len(iterable) < min(cpu_count, 4)) or select().Worker.nested:  # serial case
 
         def tqdm_chunks(chunks: Chunks, *args, **kwargs) -> Iterable[Iteration]:  # noqa
             with tqdm(*args, **kwargs) as b:
diff --git a/pyproject.toml b/pyproject.toml
index a048f76..6c1ed24 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "parfor"
-version = "2024.10.0"
+version = "2024.10.1"
 description = "A package to mimic the use of parfor as done in Matlab."
 authors = ["Wim Pomp <wimpomp@gmail.com>"]
 license = "GPLv3"