issue a user warning if random is None

mesa/agent.py

@@ -120,6 +120,11 @@
             random (Random): the random number generator
         """
         if random is None:
+            warnings.warn(
+                "Random number generator not specified, this can make models non-reproducible. Please pass a random number generator explicitly",
+                UserWarning,
+                stacklevel=2,
+            )
             random = (
                 Random()
             )  # FIXME see issue 1981, how to get the central rng from model

mesa/examples/advanced/pd_grid/model.py

@@ -27,7 +27,7 @@ def __init__(
         """
         super().__init__(seed=seed)
         self.activation_order = activation_order
-        self.grid = OrthogonalMooreGrid((width, height), torus=True)
+        self.grid = OrthogonalMooreGrid((width, height), torus=True, random=self.random)
 
         if payoffs is not None:
             self.payoff = payoffs

mesa/examples/advanced/sugarscape_g1mt/model.py

@@ -70,7 +70,9 @@ def __init__(
         self.running = True
 
         # initiate mesa grid class
-        self.grid = OrthogonalVonNeumannGrid((self.width, self.height), torus=False)
+        self.grid = OrthogonalVonNeumannGrid(
+            (self.width, self.height), torus=False, random=self.random
+        )
         # initiate datacollector
         self.datacollector = mesa.DataCollector(
             model_reporters={

mesa/experimental/cell_space/cell_collection.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import itertools
+import warnings
 from collections.abc import Callable, Iterable, Mapping
 from functools import cached_property
 from random import Random
@@ -45,7 +46,12 @@ def __init__(
         self._capacity: int = next(iter(self._cells.keys())).capacity
 
         if random is None:
-            random = Random()  # FIXME
+            warnings.warn(
+                "Random number generator not specified, this can make models non-reproducible. Please pass a random number generator explicitly",
+                UserWarning,
+                stacklevel=2,
+            )
+            random = Random()
         self.random = random
 
     def __iter__(self):  # noqa
@@ -115,4 +121,4 @@ def cell_generator(filter_func, at_most):
                     yield cell
                     count += 1
 
-        return CellCollection(cell_generator(filter_func, at_most))
+        return CellCollection(cell_generator(filter_func, at_most), random=self.random)

mesa/experimental/cell_space/discrete_space.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import warnings
 from collections.abc import Callable
 from functools import cached_property
 from random import Random
@@ -44,7 +45,12 @@ def __init__(
         self.capacity = capacity
         self._cells: dict[tuple[int, ...], T] = {}
         if random is None:
-            random = Random()  # FIXME should default to default rng from model
+            warnings.warn(
+                "Random number generator not specified, this can make models non-reproducible. Please pass a random number generator explicitly",
+                UserWarning,
+                stacklevel=2,
+            )
+            random = Random()
         self.random = random
         self.cell_klass = cell_klass
 
@@ -67,7 +73,9 @@ def _connect_single_cell(self, cell: T): ...
     @cached_property
     def all_cells(self):
         """Return all cells in space."""
-        return CellCollection({cell: cell.agents for cell in self._cells.values()})
+        return CellCollection(
+            {cell: cell.agents for cell in self._cells.values()}, random=self.random
+        )
 
     def __iter__(self):  # noqa
         return iter(self._cells.values())