debugging cf execution within notebooks, implemented byte-code hashin…

…g of functions

new-docs/source/tutorial/1-getting-started.ipynb

@@ -293,6 +293,50 @@
     "print(\"\\n\".join(str(p) for p in outputs.out_file))"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Executing tasks in parallel\n",
+    "\n",
+    "By default, Pydra will use the *debug* worker, which executes each task sequentially.\n",
+    "This makes it easier to debug tasks and workflows, however, in most cases, once a workflow\n",
+    "is ready to go, a concurrent worker is preferable so tasks can be executed in parallel\n",
+    "(see [Workers](./2-advanced-execution.html#Workers)). To use multiple processes on a\n",
+    "workstation, select the `cf` worker option when executing the task/workflow.\n",
+    "\n",
+    "Note that when multiprocessing in Python on Windows and macOS (and good practice on Linux/POSIX\n",
+    "OSs for compatibility), you need to place a `if __name__ == \"__main__\"` block when\n",
+    "executing in top-level scripts to allow the script to be imported, but not executed,\n",
+    "by subprocesses."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "NameError",
+     "evalue": "name 'nifti_dir' is not defined",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
+      "Cell \u001b[0;32mIn[2], line 4\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;28;01mfrom\u001b[39;00m \u001b[38;5;21;01mpydra\u001b[39;00m\u001b[38;5;21;01m.\u001b[39;00m\u001b[38;5;21;01mtasks\u001b[39;00m\u001b[38;5;21;01m.\u001b[39;00m\u001b[38;5;21;01mmrtrix3\u001b[39;00m\u001b[38;5;21;01m.\u001b[39;00m\u001b[38;5;21;01mv3_0\u001b[39;00m \u001b[38;5;28;01mimport\u001b[39;00m MrGrid\n\u001b[1;32m      3\u001b[0m \u001b[38;5;28;01mif\u001b[39;00m \u001b[38;5;18m__name__\u001b[39m \u001b[38;5;241m==\u001b[39m \u001b[38;5;124m\"\u001b[39m\u001b[38;5;124m__main__\u001b[39m\u001b[38;5;124m\"\u001b[39m:  \u001b[38;5;66;03m# <-- Add this block to allow the script to imported by subprocesses\u001b[39;00m\n\u001b[0;32m----> 4\u001b[0m     mrgrid \u001b[38;5;241m=\u001b[39m MrGrid(operation\u001b[38;5;241m=\u001b[39m\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mregrid\u001b[39m\u001b[38;5;124m\"\u001b[39m, voxel\u001b[38;5;241m=\u001b[39m(\u001b[38;5;241m0.5\u001b[39m,\u001b[38;5;241m0.5\u001b[39m,\u001b[38;5;241m0.5\u001b[39m))\u001b[38;5;241m.\u001b[39msplit(in_file\u001b[38;5;241m=\u001b[39m\u001b[43mnifti_dir\u001b[49m\u001b[38;5;241m.\u001b[39miterdir())\n\u001b[1;32m      5\u001b[0m     outputs \u001b[38;5;241m=\u001b[39m mrgrid(worker\u001b[38;5;241m=\u001b[39m\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mcf\u001b[39m\u001b[38;5;124m\"\u001b[39m)  \u001b[38;5;66;03m# <-- Select the \"cf\" worker here\u001b[39;00m\n\u001b[1;32m      6\u001b[0m     \u001b[38;5;28mprint\u001b[39m(\u001b[38;5;124m\"\u001b[39m\u001b[38;5;130;01m\\n\u001b[39;00m\u001b[38;5;124m\"\u001b[39m\u001b[38;5;241m.\u001b[39mjoin(\u001b[38;5;28mstr\u001b[39m(p) \u001b[38;5;28;01mfor\u001b[39;00m p \u001b[38;5;129;01min\u001b[39;00m outputs\u001b[38;5;241m.\u001b[39mout_file))\n",
+      "\u001b[0;31mNameError\u001b[0m: name 'nifti_dir' is not defined"
+     ]
+    }
+   ],
+   "source": [
+    "from pydra.tasks.mrtrix3.v3_0 import MrGrid\n",
+    "\n",
+    "if __name__ == \"__main__\":  # <-- Add this block to allow the script to imported by subprocesses\n",
+    "    mrgrid = MrGrid(operation=\"regrid\", voxel=(0.5,0.5,0.5)).split(in_file=nifti_dir.iterdir())\n",
+    "    outputs = mrgrid(worker=\"cf\")  # <-- Select the \"cf\" worker here\n",
+    "    print(\"\\n\".join(str(p) for p in outputs.out_file))"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},