[minor] Make ProcessPoolExecutor the default executor (#389)

* Make ProcessPoolExecutor the default executor -- but use executorlib in notebooks

* [minor] Don't have a default `Executor` (#390)

Make the user choose one specifically.

notebooks/deepdive.ipynb

@@ -3883,7 +3883,7 @@
     "\n",
     "You can currently run nodes in different process by setting that node's `executor` to an instance of a compliant executor object -- i.e. that takes the standard `submit` method of `concurrent.futures.Executor`, returns a `concurrent.futures.Future` (or sub-class). The built-in `Node` instances (workflows, macros, function nodes, etc.) are `pickle`-compliant, and thus will work with a standard `ProcessPoolExecutor` or `ThreadPoolExecutor` from `concurrent.futures`.\n",
     "\n",
-    "For the case of `ProcessPoolExecutor`, the other process needs to be able to find an import the nodes, so they can't have been created in `__main__` (e.g. here in notebook) but need to be in some importable `.py` file. You might also want to have a node holding un-pickleable data. For these cases, we make a couple more flexible executors available on the creator. There is a toy `CloudpickleProcessPoolExecutor` which is a minimal example of handling dynamically defined/un-picklable data and useful for learning, but we also link to `executorlib.Executor`, which is both flexible and powerful. This is the default `Workflow.create.Executor`.\n",
+    "For the case of `ProcessPoolExecutor`, the other process needs to be able to find an import the nodes, so they can't have been created in `__main__` (e.g. here in notebook) but need to be in some importable `.py` file. You might also want to have a node holding un-pickleable data. For these cases, we make a couple more flexible executors available on the creator. There is a toy `CloudpickleProcessPoolExecutor` which is a minimal example of handling dynamically defined/un-picklable data and useful for learning, but we also link to `executorlib.Executor`, which is both flexible and powerful. For compatibility with GitHub CI on macos, this currently also requires an extra keyword.\n",
     "\n",
     "Here's a simple example of executor usage:"
    ]
@@ -3909,7 +3909,7 @@
     "wf.a2 = wf.create.standard.Add(2, 3)\n",
     "wf.b = wf.a1 + wf.a2\n",
     "\n",
-    "wf.a2.executor = wf.create.Executor()\n",
+    "wf.a2.executor = wf.create.ExecutorlibExecutor(hostname_localhost=True)\n",
     "wf()\n",
     "\n",
     "print(wf.a1.future, wf.a1.outputs.add.value)\n",
@@ -3996,7 +3996,7 @@
     }
    ],
    "source": [
-    "with Workflow.create.Executor() as executor:\n",
+    "with Workflow.create.ExecutorlibExecutor(hostname_localhost=True) as executor:\n",
     "    wf = Workflow(\"with_executor\")\n",
     "    wf.a1 = wf.create.standard.Add(0, 1)\n",
     "    wf.a2 = wf.create.standard.Add(2, 3)\n",
@@ -4093,7 +4093,7 @@
     "wf.starting_nodes = [wf.a, wf.b, wf.c]\n",
     "\n",
     "\n",
-    "with wf.create.Executor(max_workers=3) as executor:\n",
+    "with wf.create.ExecutorlibExecutor(hostname_localhost=True, max_workers=3) as executor:\n",
     "    wf.a.executor = executor\n",
     "    wf.b.executor = executor\n",
     "    wf.c.executor = executor\n",

notebooks/quickstart.ipynb

@@ -1775,7 +1775,7 @@
     "To learn more, take a look at the `deepdive.ipynb` notebook, and/or start looking through the class docstrings. Here's a brief map of what you're still missing:\n",
     "\n",
     "- Distributing node execution onto remote processes\n",
-    "  - Single core parallel python processes is available by setting the `.executor` attribute to a compatible executor instance, e.g. `Workflow.create.Executor()`\n",
+    "  - Parallel computation is available by setting the `.executor` attribute to a compatible executor instance, e.g. `Workflow.create.ProcessPoolExecutor()`\n",
     "- Acyclic graphs\n",
     "  - Execution for graphs whose data flow topology is a DAG happens automatically, but you're always free to specify this manually with `Signals`, and indeed _must_ specify the execution flow manually for cyclic graphs -- but cyclic graphs _are_ possible!\n",
     "- Complex flow nodes\n",

pyiron_workflow/create.py

@@ -24,9 +24,6 @@
 if TYPE_CHECKING:
     from pyiron_workflow.node_package import NodePackage
 
-# Specify the standard executor
-Executor = ExecutorlibExecutor
-
 
 class Creator(metaclass=Singleton):
     """
@@ -47,7 +44,6 @@ def __init__(self):
         self._package_access = DotDict()
         self._package_registry = bidict()
 
-        self.Executor = Executor
         # Standard lib
         self.ProcessPoolExecutor = ProcessPoolExecutor
         self.ThreadPoolExecutor = ThreadPoolExecutor

tests/integration/test_workflow.py

@@ -138,7 +138,7 @@ def test_executor_and_creator_interaction(self):
         wf.register("static.demo_nodes", "demo")
 
         wf.before_pickling = wf.create.demo.OptionallyAdd(1)
-        wf.before_pickling.executor = wf.create.Executor()
+        wf.before_pickling.executor = wf.create.ProcessPoolExecutor()
         wf()
         wf.before_pickling.future.result(timeout=120)  # Wait for it to finish
         wf.executor_shutdown()

tests/unit/nodes/test_macro.py

@@ -212,7 +212,7 @@ def test_with_executor(self):
         # at the downstream output, and none of this is happening in a workflow
 
         original_one = macro.one
-        macro.executor = macro.create.Executor()
+        macro.executor = macro.create.ProcessPoolExecutor()
 
         self.assertIs(
             NOT_DATA,

tests/unit/test_node.py

@@ -1,13 +1,11 @@
-from concurrent.futures import Future
+from concurrent.futures import Future, ProcessPoolExecutor
 import os
 import sys
 import unittest
 
 from pyiron_snippets.files import DirectoryObject
 
 from pyiron_workflow.channels import InputData, NOT_DATA
-
-from pyiron_workflow.create import Executor
 from pyiron_workflow.mixin.injection import OutputDataWithInjection, OutputsWithInjection
 from pyiron_workflow.io import Inputs
 from pyiron_workflow.node import Node
@@ -143,7 +141,7 @@ def test_check_readiness(self):
         )
 
     def test_force_local_execution(self):
-        self.n1.executor = Executor()
+        self.n1.executor = ProcessPoolExecutor()
         out = self.n1.run(force_local_execution=False)
         with self.subTest("Test running with an executor fulfills promises"):
             self.assertIsInstance(
@@ -179,7 +177,7 @@ def test_force_local_execution(self):
                     "happens"
             )
 
-        self.n2.executor = Executor()
+        self.n2.executor = ProcessPoolExecutor()
         self.n2.inputs.x = 0
         self.assertEqual(
             1,

tests/unit/test_workflow.py

@@ -197,7 +197,7 @@ def test_with_executor(self):
         wf.b = wf.create.function_node(plus_one, x=wf.a)
 
         original_a = wf.a
-        wf.executor = wf.create.Executor()
+        wf.executor = wf.create.ProcessPoolExecutor()
 
         self.assertIs(
             NOT_DATA,
@@ -243,7 +243,7 @@ def test_parallel_execution(self):
         wf.fast = five()
         wf.sum = sum(a=wf.fast, b=wf.slow)
 
-        wf.slow.executor = wf.create.Executor()
+        wf.slow.executor = wf.create.ProcessPoolExecutor()
 
         wf.slow.run()
         wf.fast.run()
@@ -419,7 +419,7 @@ def add_three_macro(self, one__x):
             msg="Sanity check, pulling here should work perfectly fine"
         )
 
-        wf.m.one.executor = wf.create.Executor()
+        wf.m.one.executor = wf.create.ProcessPoolExecutor()
         with self.assertRaises(
             ValueError,
             msg="Should not be able to pull with executor in local scope"
@@ -428,7 +428,7 @@ def add_three_macro(self, one__x):
             wf.m.one.executor_shutdown()  # Shouldn't get this far, but if so, shutdown
         wf.m.one.executor = None
 
-        wf.n1.executor = wf.create.Executor()
+        wf.n1.executor = wf.create.ProcessPoolExecutor()
         with self.assertRaises(
             ValueError,
             msg="Should not be able to pull with executor in parent scope"