Example of using joblib to run systemcalls in parallel complete with ipy magics

joblib_poc.ipynb

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   "source": [
    "import subprocess\n",
    "import functools\n",
    "from IPython.core.magic import line_magic, Magics, magics_class, line_cell_magic\n",
    "import joblib\n",
    "\n",
    "\n",
    "def systemcall(to_exec):\n",
    "    proc = subprocess.Popen(to_exec, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)\n",
    "    stdout, stderr = proc.communicate()\n",
    "    retval = proc.returncode\n",
    "\n",
    "    return(stdout, stderr, retval)\n",
    "\n",
    "\n",
    "@magics_class\n",
    "class JobManager(Magics):\n",
    "    jobs = []\n",
    "    ncpus = 2\n",
    "    \n",
    "    def __init__(self, shell, systemcaller):\n",
    "        super(JobManager, self).__init__(shell)\n",
    "        self.shell = shell\n",
    "        self.systemcall = systemcaller\n",
    "        \n",
    "    @line_magic\n",
    "    def stage(self, line):\n",
    "        self.jobs.append(line)\n",
    "        \n",
    "    @line_cell_magic\n",
    "    def execute(self, line, cell=None):\n",
    "        if cell is not None:\n",
    "            self.shell.run_cell(cell)\n",
    "            \n",
    "        to_run = self.jobs\n",
    "        self.jobs = []\n",
    "        \n",
    "        if to_run:\n",
    "            return joblib.Parallel(n_jobs=self.ncpus)(joblib.delayed(self.systemcall)(f) for f in to_run)\n",
    "        else:\n",
    "            return []\n",
    "    \n",
    "    \n",
    "ip = get_ipython()\n",
    "magics = JobManager(ip, systemcall)\n",
    "ip.register_magics(magics)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Stage and run some commands in parallel. Displaying cell runtime as, with 2 processors, we expect 1 to be blocked with the delay, and the other processor to execute the remaining trivial tasks. As such, we expect walltime here to be approximately `==` to `delay`. Note that passing variables as works as with the `!` syntax."
   ]
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   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "10.142510175704956\n"
     ]
    }
   ],
   "source": [
    "import time\n",
    "start = time.time()\n",
    "delay = 10\n",
    "%stage sleep $delay\n",
    "%stage hostname\n",
    "%stage uptime\n",
    "%stage foobar\n",
    "%execute\n",
    "print(time.time() - start)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We just executed in the prior cell, so there should be nothing to execute now."
   ]
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  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
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   "outputs": [
    {
     "data": {
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       "[]"
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     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "%execute"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can also use a \"cell magic\" which will automagically run the staged commands in the cell."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "data": {
      "text/plain": [
       "[(b'sandbar.local\\n', b'', 0),\n",
       " (b'15:11  up 23:02, 7 users, load averages: 1.68 1.59 1.57\\n', b'', 0),\n",
       " (b'', b'', 0),\n",
       " (b'', b'/bin/sh: foobar: command not found\\n', 127)]"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "%%execute\n",
    "delay = 2\n",
    "%stage hostname\n",
    "%stage uptime\n",
    "%stage sleep $delay\n",
    "%stage foobar"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "UsageError: %%execute is a cell magic, but the cell body is empty. Did you mean the line magic %execute (single %)?"
     ]
    }
   ],
   "source": [
    "%%execute"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
  }
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