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   "source": [
    "# Deriving evolver and driver classes\n",
    "\n",
    "In `micromagneticmodel` package, base classes `micromagneticmodel.Driver` and `micromagneticmodel.Evolver` are defined. Their purpose is to build individual evolvers and drivers in a particular micromagnetic calculator. In this tutorial, we will demonstrate some of their basic properties, on an example of a `micromagneticmodel.Driver` class. The behaviour of the `micromagneticmodel.Evolver` class is the same.\n",
    "\n",
    "Let us derive `MyDriver` class. In order to define it, `_allowed_attributes` list must be defined. It is a list of strings, which lists the kwargs which are allowed to be passed. Additionally, the driver must define a property `_x` for the independent variable (e.g. time)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "import micromagneticmodel as mm\n",
    "\n",
    "\n",
    "class MyDriver(mm.Driver):\n",
    "    _allowed_attributes = [\"arg1\", \"arg2\"]\n",
    "\n",
    "    @property\n",
    "    def _x(self):\n",
    "        return \"t\"\n",
    "\n",
    "    def drive(system):\n",
    "        return system"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "`Driver` class does not require any parameters to be passed at initialisation. If a keyword argument is from `_allowed_kwargs` list, it will be assigned as a class attribute. Otherwise, `AttributeError` will be raised."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "driver = MyDriver(arg1=1, arg2=\"value\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The attributes are"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "1"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "driver.arg1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "'value'"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "driver.arg2"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "If we try to pass a keyword argument at initialisation, which is not in the `_allowed_kwargs` list, `AttributeError` is rased:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Exception raised.\n"
     ]
    }
   ],
   "source": [
    "try:\n",
    "    driver = MyDriver(arg3=1)\n",
    "except AttributeError:\n",
    "    print(\"Exception raised.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The main driver method which must be implemented by a derived class is `drive`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [],
   "source": [
    "try:\n",
    "    driver.drive()\n",
    "except NotImplementedError:\n",
    "    print(\"Exception raised.\")"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {
    "editable": true,
    "slideshow": {
     "slide_type": ""
    },
    "tags": []
   },
   "source": [
    "To build a driver for an existing external package class `micromagneticmodel.ExternalDriver` should be used. This class provides an additional method `schedule` to submit a calculation job to a scheduling system.\n",
    "\n",
    "Furthermore, it has a generic implementation for `drive` and `schedule` that consists of the following steps:\n",
    "- Create a directory to save the input and output in.\n",
    "- Write the input files for the existing simulation package.\n",
    "- Call the existing simulation package to run the simulation. / Schedule a job to run the simulation.\n",
    "- Update the `system` object with the simulation results (`drive` only).\n",
    "\n",
    "Simulation-package specific things such as writing input files and reading results must be implemented in a number of pre-defined abstract methods inside the derived class. Refer to the API reference for more details."
   ]
  }
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