Add Reward API Docs etc (#1910)

Co-authored-by: Chayenne <zhaochenyang@g.ucla.edu>

docs/backend/native_api.ipynb

@@ -5,9 +5,10 @@
    "metadata": {},
    "source": [
     "# Native APIs\n",
+    "\n",
     "Apart from the OpenAI compatible APIs, the SGLang Runtime also provides its native server APIs. We introduce these following APIs:\n",
     "\n",
-    "- `/generate`\n",
+    "- `/generate` (text generation model)\n",
     "- `/get_server_args`\n",
     "- `/get_model_info`\n",
     "- `/health`\n",
@@ -15,7 +16,8 @@
     "- `/flush_cache`\n",
     "- `/get_memory_pool_size`\n",
     "- `/update_weights`\n",
-    "- `/encode`\n",
+    "- `/encode`(embedding model)\n",
+    "- `/judge`(reward model)\n",
     "\n",
     "We mainly use `requests` to test these APIs in the following examples. You can also use `curl`."
    ]
@@ -40,6 +42,8 @@
     "    print_highlight,\n",
     ")\n",
     "\n",
+    "import requests\n",
+    "\n",
     "server_process = execute_shell_command(\n",
     "    \"\"\"\n",
     "python3 -m sglang.launch_server --model-path meta-llama/Llama-3.2-1B-Instruct --port=30010\n",
@@ -53,7 +57,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Generate\n",
+    "## Generate (text generation model)\n",
     "Generate completions. This is similar to the `/v1/completions` in OpenAI API. Detailed parameters can be found in the [sampling parameters](../references/sampling_params.html)."
    ]
   },
@@ -63,8 +67,6 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "import requests\n",
-    "\n",
     "url = \"http://localhost:30010/generate\"\n",
     "data = {\"text\": \"What is the capital of France?\"}\n",
     "\n",
@@ -252,7 +254,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "## Encode\n",
+    "## Encode (embedding model)\n",
     "\n",
     "Encode text into embeddings. Note that this API is only available for [embedding models](openai_api_embeddings.html#openai-apis-embedding) and will raise an error for generation models.\n",
     "Therefore, we launch a new server to server an embedding model."
@@ -292,13 +294,76 @@
     "print_highlight(f\"Text embedding (first 10): {response_json['embedding'][:10]}\")"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Judge (reward model)\n",
+    "\n",
+    "SGLang Runtime also supports reward models. Here we use a reward model to judge the quality of pairwise generations."
+   ]
+  },
   {
    "cell_type": "code",
-   "execution_count": 43,
+   "execution_count": null,
    "metadata": {},
    "outputs": [],
    "source": [
-    "terminate_process(embedding_process)"
+    "terminate_process(embedding_process)\n",
+    "\n",
+    "# Note that SGLang now treats embedding models and reward models as the same type of models.\n",
+    "# This will be updated in the future.\n",
+    "\n",
+    "reward_process = execute_shell_command(\n",
+    "    \"\"\"\n",
+    "python -m sglang.launch_server --model-path Skywork/Skywork-Reward-Llama-3.1-8B-v0.2 --port 30030 --host 0.0.0.0 --is-embedding\n",
+    "\"\"\"\n",
+    ")\n",
+    "\n",
+    "wait_for_server(\"http://localhost:30030\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from transformers import AutoTokenizer\n",
+    "\n",
+    "PROMPT = (\n",
+    "    \"What is the range of the numeric output of a sigmoid node in a neural network?\"\n",
+    ")\n",
+    "\n",
+    "RESPONSE1 = \"The output of a sigmoid node is bounded between -1 and 1.\"\n",
+    "RESPONSE2 = \"The output of a sigmoid node is bounded between 0 and 1.\"\n",
+    "\n",
+    "CONVS = [\n",
+    "    [{\"role\": \"user\", \"content\": PROMPT}, {\"role\": \"assistant\", \"content\": RESPONSE1}],\n",
+    "    [{\"role\": \"user\", \"content\": PROMPT}, {\"role\": \"assistant\", \"content\": RESPONSE2}],\n",
+    "]\n",
+    "\n",
+    "tokenizer = AutoTokenizer.from_pretrained(\"Skywork/Skywork-Reward-Llama-3.1-8B-v0.2\")\n",
+    "prompts = tokenizer.apply_chat_template(CONVS, tokenize=False)\n",
+    "\n",
+    "url = \"http://localhost:30030/judge\"\n",
+    "data = {\n",
+    "    \"model\": \"Skywork/Skywork-Reward-Llama-3.1-8B-v0.2\", \n",
+    "    \"text\": prompts\n",
+    "}\n",
+    "\n",
+    "responses = requests.post(url, json=data).json()\n",
+    "for response in responses:\n",
+    "    print_highlight(f\"reward: {response['embedding'][0]}\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 15,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "terminate_process(reward_process)"
    ]
   }
  ],