Add NumPy random seed to notebook instead (#4847)

Co-authored-by: Eric G. Kratz <[email protected]>

docs/source/examples/notebooks/models/half-cell.ipynb

@@ -37,6 +37,26 @@
     "import matplotlib.pyplot as plt"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "2b2e62ad",
+   "metadata": {},
+   "source": [
+    "First, we introduce a random seed to ensure reproducibility of the results before running the simulation:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "7f30409c",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import numpy as np\n",
+    "\n",
+    "np.random.seed(42)"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "f372aa29",

src/pybamm/simulation.py

@@ -2,7 +2,6 @@
 import pickle
 import pybamm
 import numpy as np
-import hashlib
 import warnings
 from functools import lru_cache
 from datetime import timedelta
@@ -133,9 +132,6 @@ def __init__(
         self._solution = None
         self.quick_plot = None
 
-        # Initialise instances of Simulation class with the same random seed
-        self._set_random_seed()
-
         # ignore runtime warnings in notebooks
         if is_notebook():  # pragma: no cover
             import warnings
@@ -159,18 +155,6 @@ def __setstate__(self, state):
         self.__dict__ = state
         self.get_esoh_solver = lru_cache()(self._get_esoh_solver)
 
-    # If the solver being used is CasadiSolver or its variants, set a fixed
-    # random seed during class initialization to the SHA-256 hash of the class
-    # name for purposes of reproducibility.
-    def _set_random_seed(self):
-        if isinstance(self._solver, pybamm.CasadiSolver) or isinstance(
-            self._solver, pybamm.CasadiAlgebraicSolver
-        ):
-            np.random.seed(
-                int(hashlib.sha256(self.__class__.__name__.encode()).hexdigest(), 16)
-                % (2**32)
-            )
-
     def set_up_and_parameterise_experiment(self, solve_kwargs=None):
         msg = "pybamm.simulation.set_up_and_parameterise_experiment is deprecated and not meant to be accessed by users."
         warnings.warn(msg, DeprecationWarning, stacklevel=2)