diff --git a/ch02/01_main-chapter-code/ch02.ipynb b/ch02/01_main-chapter-code/ch02.ipynb
index 005a9e2..72c43fa 100644
--- a/ch02/01_main-chapter-code/ch02.ipynb
+++ b/ch02/01_main-chapter-code/ch02.ipynb
@@ -26,7 +26,7 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "torch version: 2.1.0\n",
+      "torch version: 2.2.1\n",
       "tiktoken version: 0.5.1\n"
      ]
     }
@@ -559,7 +559,7 @@
       "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
       "\u001b[0;31mKeyError\u001b[0m                                  Traceback (most recent call last)",
       "Cell \u001b[0;32mIn[16], line 5\u001b[0m\n\u001b[1;32m      1\u001b[0m tokenizer \u001b[38;5;241m=\u001b[39m SimpleTokenizerV1(vocab)\n\u001b[1;32m      3\u001b[0m text \u001b[38;5;241m=\u001b[39m \u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mHello, do you like tea. Is this-- a test?\u001b[39m\u001b[38;5;124m\"\u001b[39m\n\u001b[0;32m----> 5\u001b[0m \u001b[43mtokenizer\u001b[49m\u001b[38;5;241;43m.\u001b[39;49m\u001b[43mencode\u001b[49m\u001b[43m(\u001b[49m\u001b[43mtext\u001b[49m\u001b[43m)\u001b[49m\n",
-      "Cell \u001b[0;32mIn[12], line 9\u001b[0m, in \u001b[0;36mSimpleTokenizerV1.encode\u001b[0;34m(self, text)\u001b[0m\n\u001b[1;32m      7\u001b[0m preprocessed \u001b[38;5;241m=\u001b[39m re\u001b[38;5;241m.\u001b[39msplit(\u001b[38;5;124mr\u001b[39m\u001b[38;5;124m'\u001b[39m\u001b[38;5;124m([,.?_!\u001b[39m\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124m()\u001b[39m\u001b[38;5;130;01m\\'\u001b[39;00m\u001b[38;5;124m]|--|\u001b[39m\u001b[38;5;124m\\\u001b[39m\u001b[38;5;124ms)\u001b[39m\u001b[38;5;124m'\u001b[39m, text)\n\u001b[1;32m      8\u001b[0m preprocessed \u001b[38;5;241m=\u001b[39m [item\u001b[38;5;241m.\u001b[39mstrip() \u001b[38;5;28;01mfor\u001b[39;00m item \u001b[38;5;129;01min\u001b[39;00m preprocessed \u001b[38;5;28;01mif\u001b[39;00m item\u001b[38;5;241m.\u001b[39mstrip()]\n\u001b[0;32m----> 9\u001b[0m ids \u001b[38;5;241m=\u001b[39m [\u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mstr_to_int[s] \u001b[38;5;28;01mfor\u001b[39;00m s \u001b[38;5;129;01min\u001b[39;00m preprocessed]\n\u001b[1;32m     10\u001b[0m \u001b[38;5;28;01mreturn\u001b[39;00m ids\n",
+      "Cell \u001b[0;32mIn[12], line 9\u001b[0m, in \u001b[0;36mSimpleTokenizerV1.encode\u001b[0;34m(self, text)\u001b[0m\n\u001b[1;32m      7\u001b[0m preprocessed \u001b[38;5;241m=\u001b[39m re\u001b[38;5;241m.\u001b[39msplit(\u001b[38;5;124mr\u001b[39m\u001b[38;5;124m'\u001b[39m\u001b[38;5;124m([,.?_!\u001b[39m\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124m()\u001b[39m\u001b[38;5;130;01m\\'\u001b[39;00m\u001b[38;5;124m]|--|\u001b[39m\u001b[38;5;124m\\\u001b[39m\u001b[38;5;124ms)\u001b[39m\u001b[38;5;124m'\u001b[39m, text)\n\u001b[1;32m      8\u001b[0m preprocessed \u001b[38;5;241m=\u001b[39m [item\u001b[38;5;241m.\u001b[39mstrip() \u001b[38;5;28;01mfor\u001b[39;00m item \u001b[38;5;129;01min\u001b[39;00m preprocessed \u001b[38;5;28;01mif\u001b[39;00m item\u001b[38;5;241m.\u001b[39mstrip()]\n\u001b[0;32m----> 9\u001b[0m ids \u001b[38;5;241m=\u001b[39m \u001b[43m[\u001b[49m\u001b[38;5;28;43mself\u001b[39;49m\u001b[38;5;241;43m.\u001b[39;49m\u001b[43mstr_to_int\u001b[49m\u001b[43m[\u001b[49m\u001b[43ms\u001b[49m\u001b[43m]\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;28;43;01mfor\u001b[39;49;00m\u001b[43m \u001b[49m\u001b[43ms\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;129;43;01min\u001b[39;49;00m\u001b[43m \u001b[49m\u001b[43mpreprocessed\u001b[49m\u001b[43m]\u001b[49m\n\u001b[1;32m     10\u001b[0m \u001b[38;5;28;01mreturn\u001b[39;00m ids\n",
       "Cell \u001b[0;32mIn[12], line 9\u001b[0m, in \u001b[0;36m<listcomp>\u001b[0;34m(.0)\u001b[0m\n\u001b[1;32m      7\u001b[0m preprocessed \u001b[38;5;241m=\u001b[39m re\u001b[38;5;241m.\u001b[39msplit(\u001b[38;5;124mr\u001b[39m\u001b[38;5;124m'\u001b[39m\u001b[38;5;124m([,.?_!\u001b[39m\u001b[38;5;124m\"\u001b[39m\u001b[38;5;124m()\u001b[39m\u001b[38;5;130;01m\\'\u001b[39;00m\u001b[38;5;124m]|--|\u001b[39m\u001b[38;5;124m\\\u001b[39m\u001b[38;5;124ms)\u001b[39m\u001b[38;5;124m'\u001b[39m, text)\n\u001b[1;32m      8\u001b[0m preprocessed \u001b[38;5;241m=\u001b[39m [item\u001b[38;5;241m.\u001b[39mstrip() \u001b[38;5;28;01mfor\u001b[39;00m item \u001b[38;5;129;01min\u001b[39;00m preprocessed \u001b[38;5;28;01mif\u001b[39;00m item\u001b[38;5;241m.\u001b[39mstrip()]\n\u001b[0;32m----> 9\u001b[0m ids \u001b[38;5;241m=\u001b[39m [\u001b[38;5;28;43mself\u001b[39;49m\u001b[38;5;241;43m.\u001b[39;49m\u001b[43mstr_to_int\u001b[49m\u001b[43m[\u001b[49m\u001b[43ms\u001b[49m\u001b[43m]\u001b[49m \u001b[38;5;28;01mfor\u001b[39;00m s \u001b[38;5;129;01min\u001b[39;00m preprocessed]\n\u001b[1;32m     10\u001b[0m \u001b[38;5;28;01mreturn\u001b[39;00m ids\n",
       "\u001b[0;31mKeyError\u001b[0m: 'Hello'"
      ]
@@ -585,7 +585,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": null,
    "id": "ce9df29c-6c5b-43f1-8c1a-c7f7b79db78f",
    "metadata": {},
    "outputs": [],
@@ -601,17 +601,17 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 18,
+   "execution_count": 17,
    "id": "57c3143b-e860-4d3b-a22a-de22b547a6a9",
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "1161"
+       "1159"
       ]
      },
-     "execution_count": 18,
+     "execution_count": 17,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -622,7 +622,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 19,
+   "execution_count": 18,
    "id": "50e51bb1-ae05-4aa8-a9ff-455b65ed1959",
    "metadata": {},
    "outputs": [
@@ -630,11 +630,11 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
+      "('yet', 1154)\n",
+      "('you', 1155)\n",
       "('younger', 1156)\n",
       "('your', 1157)\n",
-      "('yourself', 1158)\n",
-      "('<|endoftext|>', 1159)\n",
-      "('<|unk|>', 1160)\n"
+      "('yourself', 1158)\n"
      ]
     }
    ],
@@ -653,7 +653,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 20,
+   "execution_count": 19,
    "id": "948861c5-3f30-4712-a234-725f20d26f68",
    "metadata": {},
    "outputs": [],
@@ -689,7 +689,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 21,
+   "execution_count": 20,
    "id": "effcef79-e0a5-4f4a-a43a-31dd94b9250a",
    "metadata": {},
    "outputs": [
@@ -714,34 +714,22 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 22,
+   "execution_count": 21,
    "id": "ddfe7346-398d-4bf8-99f1-5b071244ce95",
    "metadata": {},
    "outputs": [
     {
-     "data": {
-      "text/plain": [
-       "[1160,\n",
-       " 5,\n",
-       " 362,\n",
-       " 1155,\n",
-       " 642,\n",
-       " 1000,\n",
-       " 10,\n",
-       " 1159,\n",
-       " 57,\n",
-       " 1013,\n",
-       " 981,\n",
-       " 1009,\n",
-       " 738,\n",
-       " 1013,\n",
-       " 1160,\n",
-       " 7]"
-      ]
-     },
-     "execution_count": 22,
-     "metadata": {},
-     "output_type": "execute_result"
+     "ename": "KeyError",
+     "evalue": "'<|unk|>'",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mKeyError\u001b[0m                                  Traceback (most recent call last)",
+      "Cell \u001b[0;32mIn[21], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mtokenizer\u001b[49m\u001b[38;5;241;43m.\u001b[39;49m\u001b[43mencode\u001b[49m\u001b[43m(\u001b[49m\u001b[43mtext\u001b[49m\u001b[43m)\u001b[49m\n",
+      "Cell \u001b[0;32mIn[19], line 12\u001b[0m, in \u001b[0;36mSimpleTokenizerV2.encode\u001b[0;34m(self, text)\u001b[0m\n\u001b[1;32m      8\u001b[0m preprocessed \u001b[38;5;241m=\u001b[39m [item\u001b[38;5;241m.\u001b[39mstrip() \u001b[38;5;28;01mfor\u001b[39;00m item \u001b[38;5;129;01min\u001b[39;00m preprocessed \u001b[38;5;28;01mif\u001b[39;00m item\u001b[38;5;241m.\u001b[39mstrip()]\n\u001b[1;32m      9\u001b[0m preprocessed \u001b[38;5;241m=\u001b[39m [item \u001b[38;5;28;01mif\u001b[39;00m item \u001b[38;5;129;01min\u001b[39;00m \u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mstr_to_int \n\u001b[1;32m     10\u001b[0m                 \u001b[38;5;28;01melse\u001b[39;00m \u001b[38;5;124m\"\u001b[39m\u001b[38;5;124m<|unk|>\u001b[39m\u001b[38;5;124m\"\u001b[39m \u001b[38;5;28;01mfor\u001b[39;00m item \u001b[38;5;129;01min\u001b[39;00m preprocessed]\n\u001b[0;32m---> 12\u001b[0m ids \u001b[38;5;241m=\u001b[39m \u001b[43m[\u001b[49m\u001b[38;5;28;43mself\u001b[39;49m\u001b[38;5;241;43m.\u001b[39;49m\u001b[43mstr_to_int\u001b[49m\u001b[43m[\u001b[49m\u001b[43ms\u001b[49m\u001b[43m]\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;28;43;01mfor\u001b[39;49;00m\u001b[43m \u001b[49m\u001b[43ms\u001b[49m\u001b[43m \u001b[49m\u001b[38;5;129;43;01min\u001b[39;49;00m\u001b[43m \u001b[49m\u001b[43mpreprocessed\u001b[49m\u001b[43m]\u001b[49m\n\u001b[1;32m     13\u001b[0m \u001b[38;5;28;01mreturn\u001b[39;00m ids\n",
+      "Cell \u001b[0;32mIn[19], line 12\u001b[0m, in \u001b[0;36m<listcomp>\u001b[0;34m(.0)\u001b[0m\n\u001b[1;32m      8\u001b[0m preprocessed \u001b[38;5;241m=\u001b[39m [item\u001b[38;5;241m.\u001b[39mstrip() \u001b[38;5;28;01mfor\u001b[39;00m item \u001b[38;5;129;01min\u001b[39;00m preprocessed \u001b[38;5;28;01mif\u001b[39;00m item\u001b[38;5;241m.\u001b[39mstrip()]\n\u001b[1;32m      9\u001b[0m preprocessed \u001b[38;5;241m=\u001b[39m [item \u001b[38;5;28;01mif\u001b[39;00m item \u001b[38;5;129;01min\u001b[39;00m \u001b[38;5;28mself\u001b[39m\u001b[38;5;241m.\u001b[39mstr_to_int \n\u001b[1;32m     10\u001b[0m                 \u001b[38;5;28;01melse\u001b[39;00m \u001b[38;5;124m\"\u001b[39m\u001b[38;5;124m<|unk|>\u001b[39m\u001b[38;5;124m\"\u001b[39m \u001b[38;5;28;01mfor\u001b[39;00m item \u001b[38;5;129;01min\u001b[39;00m preprocessed]\n\u001b[0;32m---> 12\u001b[0m ids \u001b[38;5;241m=\u001b[39m [\u001b[38;5;28;43mself\u001b[39;49m\u001b[38;5;241;43m.\u001b[39;49m\u001b[43mstr_to_int\u001b[49m\u001b[43m[\u001b[49m\u001b[43ms\u001b[49m\u001b[43m]\u001b[49m \u001b[38;5;28;01mfor\u001b[39;00m s \u001b[38;5;129;01min\u001b[39;00m preprocessed]\n\u001b[1;32m     13\u001b[0m \u001b[38;5;28;01mreturn\u001b[39;00m ids\n",
+      "\u001b[0;31mKeyError\u001b[0m: '<|unk|>'"
+     ]
     }
    ],
    "source": [
@@ -750,21 +738,10 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 23,
+   "execution_count": null,
    "id": "0c350ff6-2734-4e84-9ec7-d578baa4ae1b",
    "metadata": {},
-   "outputs": [
-    {
-     "data": {
-      "text/plain": [
-       "'<|unk|>, do you like tea? <|endoftext|> In the sunlit terraces of the <|unk|>.'"
-      ]
-     },
-     "execution_count": 23,
-     "metadata": {},
-     "output_type": "execute_result"
-    }
-   ],
+   "outputs": [],
    "source": [
     "tokenizer.decode(tokenizer.encode(text))"
    ]
@@ -792,7 +769,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 24,
+   "execution_count": 22,
    "id": "ede1d41f-934b-4bf4-8184-54394a257a94",
    "metadata": {},
    "outputs": [],
@@ -802,7 +779,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 25,
+   "execution_count": 23,
    "id": "48967a77-7d17-42bf-9e92-fc619d63a59e",
    "metadata": {},
    "outputs": [
@@ -823,7 +800,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 26,
+   "execution_count": 24,
    "id": "6ad3312f-a5f7-4efc-9d7d-8ea09d7b5128",
    "metadata": {},
    "outputs": [],
@@ -833,7 +810,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 27,
+   "execution_count": 25,
    "id": "5ff2cd85-7cfb-4325-b390-219938589428",
    "metadata": {},
    "outputs": [
@@ -855,7 +832,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 28,
+   "execution_count": 26,
    "id": "d26a48bb-f82e-41a8-a955-a1c9cf9d50ab",
    "metadata": {},
    "outputs": [
@@ -883,7 +860,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 32,
+   "execution_count": 27,
    "id": "848d5ade-fd1f-46c3-9e31-1426e315c71b",
    "metadata": {},
    "outputs": [
@@ -914,7 +891,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 33,
+   "execution_count": 28,
    "id": "e84424a7-646d-45b6-99e3-80d15fb761f2",
    "metadata": {},
    "outputs": [],
@@ -924,7 +901,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 34,
+   "execution_count": 29,
    "id": "dfbff852-a92f-48c8-a46d-143a0f109f40",
    "metadata": {},
    "outputs": [
@@ -957,7 +934,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 35,
+   "execution_count": 30,
    "id": "d97b031e-ed55-409d-95f2-aeb38c6fe366",
    "metadata": {},
    "outputs": [
@@ -982,7 +959,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 36,
+   "execution_count": 31,
    "id": "f57bd746-dcbf-4433-8e24-ee213a8c34a1",
    "metadata": {},
    "outputs": [
@@ -1024,7 +1001,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 37,
+   "execution_count": 32,
    "id": "e1770134-e7f3-4725-a679-e04c3be48cac",
    "metadata": {},
    "outputs": [
@@ -1032,7 +1009,7 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "PyTorch version: 2.1.0\n"
+      "PyTorch version: 2.2.1\n"
      ]
     }
    ],
@@ -1051,7 +1028,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 38,
+   "execution_count": 33,
    "id": "74b41073-4c9f-46e2-a1bd-d38e4122b375",
    "metadata": {},
    "outputs": [],
@@ -1084,7 +1061,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 39,
+   "execution_count": 34,
    "id": "5eb30ebe-97b3-43c5-9ff1-a97d621b3c4e",
    "metadata": {},
    "outputs": [],
@@ -1114,7 +1091,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 40,
+   "execution_count": 35,
    "id": "df31d96c-6bfd-4564-a956-6192242d7579",
    "metadata": {},
    "outputs": [],
@@ -1125,7 +1102,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 41,
+   "execution_count": 36,
    "id": "9226d00c-ad9a-4949-a6e4-9afccfc7214f",
    "metadata": {},
    "outputs": [
@@ -1147,7 +1124,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 42,
+   "execution_count": 37,
    "id": "10deb4bc-4de1-4d20-921e-4b1c7a0e1a6d",
    "metadata": {},
    "outputs": [
@@ -1175,7 +1152,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 43,
+   "execution_count": 38,
    "id": "1916e7a6-f03d-4f09-91a6-d0bdbac5a58c",
    "metadata": {},
    "outputs": [
@@ -1242,7 +1219,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 44,
+   "execution_count": 39,
    "id": "15a6304c-9474-4470-b85d-3991a49fa653",
    "metadata": {},
    "outputs": [],
@@ -1260,7 +1237,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 45,
+   "execution_count": 40,
    "id": "93cb2cee-9aa6-4bb8-8977-c65661d16eda",
    "metadata": {},
    "outputs": [],
@@ -1282,7 +1259,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 46,
+   "execution_count": 41,
    "id": "a686eb61-e737-4351-8f1c-222913d47468",
    "metadata": {},
    "outputs": [
@@ -1323,7 +1300,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 47,
+   "execution_count": 42,
    "id": "e43600ba-f287-4746-8ddf-d0f71a9023ca",
    "metadata": {},
    "outputs": [
@@ -1350,7 +1327,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 48,
+   "execution_count": 43,
    "id": "50280ead-0363-44c8-8c35-bb885d92c8b7",
    "metadata": {},
    "outputs": [
@@ -1388,7 +1365,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 49,
+   "execution_count": 44,
    "id": "0b9e344d-03a6-4f2c-b723-67b6a20c5041",
    "metadata": {},
    "outputs": [],
@@ -1410,20 +1387,20 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 50,
+   "execution_count": 45,
    "id": "ad56a263-3d2e-4d91-98bf-d0b68d3c7fc3",
    "metadata": {},
    "outputs": [],
    "source": [
     "max_length = 4\n",
-    "dataloader = create_dataloader_v1(raw_text, batch_size=8, max_length=max_length, stride=5, shuffle=False)\n",
+    "dataloader = create_dataloader_v1(raw_text, batch_size=8, max_length=max_length, stride=max_length, shuffle=False)\n",
     "data_iter = iter(dataloader)\n",
     "inputs, targets = next(data_iter)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 51,
+   "execution_count": 46,
    "id": "84416b60-3707-4370-bcbc-da0b62f2b64d",
    "metadata": {},
    "outputs": [
@@ -1433,13 +1410,13 @@
      "text": [
       "Token IDs:\n",
       " tensor([[   40,   367,  2885,  1464],\n",
-      "        [ 3619,   402,   271, 10899],\n",
-      "        [  257,  7026, 15632,   438],\n",
-      "        [  257,   922,  5891,  1576],\n",
+      "        [ 1807,  3619,   402,   271],\n",
+      "        [10899,  2138,   257,  7026],\n",
+      "        [15632,   438,  2016,   257],\n",
+      "        [  922,  5891,  1576,   438],\n",
       "        [  568,   340,   373,   645],\n",
-      "        [ 5975,   284,   502,   284],\n",
-      "        [  326,    11,   287,   262],\n",
-      "        [  286,   465, 13476,    11]])\n",
+      "        [ 1049,  5975,   284,   502],\n",
+      "        [  284,  3285,   326,    11]])\n",
       "\n",
       "Inputs shape:\n",
       " torch.Size([8, 4])\n"
@@ -1453,7 +1430,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 52,
+   "execution_count": 47,
    "id": "7766ec38-30d0-4128-8c31-f49f063c43d1",
    "metadata": {},
    "outputs": [