diff --git a/forgebox/__init__.py b/forgebox/__init__.py
index ac15521..2dd5536 100644
--- a/forgebox/__init__.py
+++ b/forgebox/__init__.py
@@ -1 +1 @@
-__version__ = "0.4.17"
+__version__ = "0.4.18"
diff --git a/forgebox/_nbdev.py b/forgebox/_nbdev.py
index 7eb9377..adf7356 100644
--- a/forgebox/_nbdev.py
+++ b/forgebox/_nbdev.py
@@ -40,6 +40,7 @@
          "compare_sentences": "06_spacy.ipynb",
          "highlight": "06_spacy.ipynb",
          "FreeMap": "07_freemap.ipynb",
+         "SingleFileLiner": "09_multiprocess.ipynb",
          "Stuff": "10_loop.ipynb",
          "method4all": "10_loop.ipynb",
          "StorageCore": "10_loop.ipynb",
@@ -159,6 +160,7 @@
            "flatten.py",
            "spacy.py",
            "freemap.py",
+           "multiproc.py",
            "loop.py",
            "etl.py",
            "static_file.py",
diff --git a/forgebox/multiproc.py b/forgebox/multiproc.py
new file mode 100644
index 0000000..15fff1a
--- /dev/null
+++ b/forgebox/multiproc.py
@@ -0,0 +1,105 @@
+# AUTOGENERATED! DO NOT EDIT! File to edit: nbs/09_multiprocess.ipynb (unless otherwise specified).
+
+__all__ = ['SingleFileLiner']
+
+# Cell
+from pathlib import Path
+import logging
+from typing import List, Dict, Callable, Any, Tuple
+import random
+
+# Cell
+class SingleFileLiner:
+    """
+    Text data reading line by line for multiprocessing
+    """
+
+    def __init__(self, file_path: Path, total: int = None):
+        """
+        filepath: Path,
+            path to a textual file
+        total: int
+            if you set total to an integer, we'll have a fixed length interation object
+            if you set total to None, we'll read the file till it's over
+        """
+        self.file_path = Path(file_path)
+        global SingleFileLiner_fp
+        SingleFileLiner_fp = open(file_path, "r")
+        global text_line_num
+        text_line_num = 0
+        self.total = total
+
+    def __repr__(self) -> str:
+        return f"SingleFileLiner:\t{self.file_path}"
+
+    def __next__(self) -> str:
+        global SingleFileLiner_fp
+        line = SingleFileLiner_fp.readline()
+        global text_line_num
+        text_line_num += 1
+        if line == "":
+            if self.total is None:
+                raise StopIteration(f"SingleFileLiner file read finish")
+            logging.warning(f"looping on {self.file_path}")
+
+            self.restart()
+        return line.strip()
+
+    def __len__(self):
+        if self.total is not None:
+            return self.total
+        else:
+            raise RuntimeError(f"You have to set total for len(self)")
+
+    def __iter__(self) -> str:
+        if self.total is None:
+            while True:
+                try:
+                    yield next(self)
+                except StopIteration:
+                    # end the file reading
+                    break
+        else:
+            for i in range(self.total):
+                yield next(self)
+
+    def restart(self) -> None:
+        """resetart file reader"""
+        global SingleFileLiner_fp
+        SingleFileLiner_fp.close()
+        SingleFileLiner_fp = open(self.file_path, "r")
+
+    def split_train_test(
+            self,
+            val_ratio: float = 0.1,
+            remove_original: bool = False,
+            logging_interval: int = 1000000) -> Tuple[Path]:
+        """
+        Split the text file into train and test
+        :param val_ratio:
+        :return:
+        """
+        suffix = self.file_path.suffix
+
+        train_file_path = self.file_path.parent / \
+            f"{self.file_path.stem}_train{suffix}"
+        valid_file_path = self.file_path.parent / \
+            f"{self.file_path.stem}_valid{suffix}"
+
+        # delete the file if exists
+        if remove_original:
+            train_file_path.unlink()
+            valid_file_path.unlink()
+
+        # read and write by line
+        with open(self.file_path, "r") as f, open(
+            train_file_path, "w") as f_train, open(
+            valid_file_path, "w") as f_valid:
+            for i, line in enumerate(f):
+                if i % 1000000 == 0:
+                    logging.info(f"{i}\tlines processed")
+                if random.random() < val_ratio:
+                    f_valid.write(line)
+                else:
+                    f_train.write(line)
+        return train_file_path, valid_file_path
\ No newline at end of file
diff --git a/nbs/09_multiprocess.ipynb b/nbs/09_multiprocess.ipynb
new file mode 100644
index 0000000..6e42775
--- /dev/null
+++ b/nbs/09_multiprocess.ipynb
@@ -0,0 +1,209 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Multiprocessing Helper\n",
+    "> Things to smooth up the multiprocessing"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# default_exp multiproc"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# export\n",
+    "from pathlib import Path\n",
+    "import logging\n",
+    "from typing import List, Dict, Callable, Any, Tuple\n",
+    "import random"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Read single file line by line"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 46,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# export\n",
+    "class SingleFileLiner:\n",
+    "    \"\"\"\n",
+    "    Text data reading line by line for multiprocessing\n",
+    "    \"\"\"\n",
+    "\n",
+    "    def __init__(self, file_path: Path, total: int = None):\n",
+    "        \"\"\"\n",
+    "        filepath: Path,\n",
+    "            path to a textual file\n",
+    "        total: int\n",
+    "            if you set total to an integer, we'll have a fixed length interation object\n",
+    "            if you set total to None, we'll read the file till it's over\n",
+    "        \"\"\"\n",
+    "        self.file_path = Path(file_path)\n",
+    "        global SingleFileLiner_fp\n",
+    "        SingleFileLiner_fp = open(file_path, \"r\")\n",
+    "        global text_line_num\n",
+    "        text_line_num = 0\n",
+    "        self.total = total\n",
+    "\n",
+    "    def __repr__(self) -> str:\n",
+    "        return f\"SingleFileLiner:\\t{self.file_path}\"\n",
+    "\n",
+    "    def __next__(self) -> str:\n",
+    "        global SingleFileLiner_fp\n",
+    "        line = SingleFileLiner_fp.readline()\n",
+    "        global text_line_num\n",
+    "        text_line_num += 1\n",
+    "        if line == \"\":\n",
+    "            if self.total is None:\n",
+    "                raise StopIteration(f\"SingleFileLiner file read finish\")\n",
+    "            logging.warning(f\"looping on {self.file_path}\")\n",
+    "\n",
+    "            self.restart()\n",
+    "        return line.strip()\n",
+    "\n",
+    "    def __len__(self):\n",
+    "        if self.total is not None:\n",
+    "            return self.total\n",
+    "        else:\n",
+    "            raise RuntimeError(f\"You have to set total for len(self)\")\n",
+    "\n",
+    "    def __iter__(self) -> str:\n",
+    "        if self.total is None:\n",
+    "            while True:\n",
+    "                try:\n",
+    "                    yield next(self)\n",
+    "                except StopIteration:\n",
+    "                    # end the file reading\n",
+    "                    break\n",
+    "        else:\n",
+    "            for i in range(self.total):\n",
+    "                yield next(self)\n",
+    "\n",
+    "    def restart(self) -> None:\n",
+    "        \"\"\"resetart file reader\"\"\"\n",
+    "        global SingleFileLiner_fp\n",
+    "        SingleFileLiner_fp.close()\n",
+    "        SingleFileLiner_fp = open(self.file_path, \"r\")\n",
+    "\n",
+    "    def split_train_test(\n",
+    "            self,\n",
+    "            val_ratio: float = 0.1,\n",
+    "            remove_original: bool = False,\n",
+    "            logging_interval: int = 1000000) -> Tuple[Path]:\n",
+    "        \"\"\"\n",
+    "        Split the text file into train and test\n",
+    "        :param val_ratio:\n",
+    "        :return:\n",
+    "        \"\"\"\n",
+    "        suffix = self.file_path.suffix\n",
+    "\n",
+    "        train_file_path = self.file_path.parent / \\\n",
+    "            f\"{self.file_path.stem}_train{suffix}\"\n",
+    "        valid_file_path = self.file_path.parent / \\\n",
+    "            f\"{self.file_path.stem}_valid{suffix}\"\n",
+    "\n",
+    "        # delete the file if exists\n",
+    "        if remove_original:\n",
+    "            train_file_path.unlink()\n",
+    "            valid_file_path.unlink()\n",
+    "\n",
+    "        # read and write by line\n",
+    "        with open(self.file_path, \"r\") as f, open(\n",
+    "            train_file_path, \"w\") as f_train, open(\n",
+    "            valid_file_path, \"w\") as f_valid:\n",
+    "            for i, line in enumerate(f):\n",
+    "                if i % 1000000 == 0:\n",
+    "                    logging.info(f\"{i}\\tlines processed\")\n",
+    "                if random.random() < val_ratio:\n",
+    "                    f_valid.write(line)\n",
+    "                else:\n",
+    "                    f_train.write(line)\n",
+    "        return train_file_path, valid_file_path"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 47,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "sfl = SingleFileLiner(\"../README.md\")\n",
+    "from joblib import Parallel, delayed\n",
+    "from time import sleep"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 48,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "def get_line(x):\n",
+    "#     sleep(1)\n",
+    "    return x\n",
+    "\n",
+    "res = Parallel(backend=\"multiprocessing\", n_jobs=6)(delayed(get_line)(i) for i in sfl)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.7.4"
+  },
+  "toc": {
+   "base_numbering": 1,
+   "nav_menu": {},
+   "number_sections": true,
+   "sideBar": true,
+   "skip_h1_title": false,
+   "title_cell": "Table of Contents",
+   "title_sidebar": "Contents",
+   "toc_cell": false,
+   "toc_position": {},
+   "toc_section_display": true,
+   "toc_window_display": false
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 4
+}
diff --git a/settings.ini b/settings.ini
index b416459..fecbddf 100644
--- a/settings.ini
+++ b/settings.ini
@@ -7,7 +7,7 @@ author = xiaochen(ray) zhang
 author_email = b2ray2c@gmail.com
 copyright = xiaochen(ray) zhang
 branch = master
-version = 0.4.17
+version = 0.4.18
 min_python = 3.6
 audience = Developers
 language = English