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   "source": [
    "# Query VLM with Offline Engine\n",
    "\n",
    "This tutorial demonstrates how to use SGLang's **offline Engine API** to query VLMs. We will demonstrate usage with Qwen2.5-VL and Llama 4. This section demonstrates three different calling approaches:\n",
    "\n",
    "1. **Basic Call**: Directly pass images and text.\n",
    "2. **Processor Output**: Use HuggingFace processor for data preprocessing.\n",
    "3. **Precomputed Embeddings**: Pre-calculate image features to improve inference efficiency."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "1",
   "metadata": {},
   "source": [
    "## Understanding the Three Input Formats\n",
    "\n",
    "SGLang supports three ways to pass visual data, each optimized for different scenarios:\n",
    "\n",
    "### 1. **Raw Images** - Simplest approach\n",
    "- Pass PIL Images, file paths, URLs, or base64 strings directly\n",
    "- SGLang handles all preprocessing automatically\n",
    "- Best for: Quick prototyping, simple applications\n",
    "\n",
    "### 2. **Processor Output** - For custom preprocessing\n",
    "- Pre-process images with HuggingFace processor\n",
    "- Pass the complete processor output dict with `format: \"processor_output\"`\n",
    "- Best for: Custom image transformations, integration with existing pipelines\n",
    "- Requirement: Must use `input_ids` instead of text prompt\n",
    "\n",
    "### 3. **Precomputed Embeddings** - For maximum performance\n",
    "- Pre-calculate visual embeddings using the vision encoder\n",
    "- Pass embeddings with `format: \"precomputed_embedding\"`\n",
    "- Best for: Repeated queries on same images, caching, high-throughput serving\n",
    "- Performance gain: Avoids redundant vision encoder computation (30-50% speedup)\n",
    "\n",
    "**Key Rule**: Within a single request, use only one format for all images. Don't mix formats.\n",
    "\n",
    "The examples below demonstrate all three approaches with both Qwen2.5-VL and Llama 4 models."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "2",
   "metadata": {},
   "source": [
    "## Querying Qwen2.5-VL Model"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "3",
   "metadata": {},
   "outputs": [],
   "source": [
    "import nest_asyncio\n",
    "\n",
    "nest_asyncio.apply()\n",
    "\n",
    "import sglang.test.doc_patch  # noqa: F401\n",
    "\n",
    "model_path = \"Qwen/Qwen2.5-VL-3B-Instruct\"\n",
    "chat_template = \"qwen2-vl\"\n",
    "example_image_url = \"https://raw.githubusercontent.com/sgl-project/sglang/main/examples/assets/example_image.png\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "4",
   "metadata": {},
   "outputs": [],
   "source": [
    "from io import BytesIO\n",
    "import requests\n",
    "from PIL import Image\n",
    "\n",
    "from sglang.srt.parser.conversation import chat_templates\n",
    "\n",
    "image = Image.open(BytesIO(requests.get(example_image_url).content))\n",
    "\n",
    "conv = chat_templates[chat_template].copy()\n",
    "conv.append_message(conv.roles[0], f\"What's shown here: {conv.image_token}?\")\n",
    "conv.append_message(conv.roles[1], \"\")\n",
    "conv.image_data = [image]\n",
    "\n",
    "print(\"Generated prompt text:\")\n",
    "print(conv.get_prompt())\n",
    "print(f\"\\nImage size: {image.size}\")\n",
    "image"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "5",
   "metadata": {},
   "source": [
    "### Basic Offline Engine API Call"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "6",
   "metadata": {},
   "outputs": [],
   "source": [
    "from sglang import Engine\n",
    "\n",
    "llm = Engine(model_path=model_path, chat_template=chat_template, log_level=\"warning\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "7",
   "metadata": {},
   "outputs": [],
   "source": [
    "out = llm.generate(prompt=conv.get_prompt(), image_data=[image])\n",
    "print(\"Model response:\")\n",
    "print(out[\"text\"])"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8",
   "metadata": {},
   "source": [
    "### Call with Processor Output\n",
    "\n",
    "Using a HuggingFace processor to preprocess text and images, and passing the `processor_output` directly into `Engine.generate`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "9",
   "metadata": {},
   "outputs": [],
   "source": [
    "from transformers import AutoProcessor\n",
    "\n",
    "processor = AutoProcessor.from_pretrained(model_path, use_fast=True)\n",
    "processor_output = processor(\n",
    "    images=[image], text=conv.get_prompt(), return_tensors=\"pt\"\n",
    ")\n",
    "\n",
    "out = llm.generate(\n",
    "    input_ids=processor_output[\"input_ids\"][0].detach().cpu().tolist(),\n",
    "    image_data=[dict(processor_output, format=\"processor_output\")],\n",
    ")\n",
    "print(\"Response using processor output:\")\n",
    "print(out[\"text\"])"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "10",
   "metadata": {},
   "source": [
    "### Call with Precomputed Embeddings\n",
    "\n",
    "You can pre-calculate image features to avoid repeated visual encoding processes."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "11",
   "metadata": {},
   "outputs": [],
   "source": [
    "from transformers import AutoProcessor\n",
    "from transformers import Qwen2_5_VLForConditionalGeneration\n",
    "\n",
    "processor = AutoProcessor.from_pretrained(model_path, use_fast=True)\n",
    "model = Qwen2_5_VLForConditionalGeneration.from_pretrained(model_path).eval()\n",
    "vision = model.model.visual.cuda()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "12",
   "metadata": {},
   "outputs": [],
   "source": [
    "processor_output = processor(\n",
    "    images=[image], text=conv.get_prompt(), return_tensors=\"pt\"\n",
    ")\n",
    "\n",
    "input_ids = processor_output[\"input_ids\"][0].detach().cpu().tolist()\n",
    "\n",
    "precomputed_embeddings = vision(\n",
    "    processor_output[\"pixel_values\"].cuda(), processor_output[\"image_grid_thw\"].cuda()\n",
    ")\n",
    "precomputed_embeddings = precomputed_embeddings.pooler_output\n",
    "\n",
    "multi_modal_item = dict(\n",
    "    processor_output,\n",
    "    format=\"precomputed_embedding\",\n",
    "    feature=precomputed_embeddings,\n",
    ")\n",
    "\n",
    "out = llm.generate(input_ids=input_ids, image_data=[multi_modal_item])\n",
    "print(\"Response using precomputed embeddings:\")\n",
    "print(out[\"text\"])\n",
    "\n",
    "llm.shutdown()"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "13",
   "metadata": {},
   "source": [
    "## Querying Llama 4 Vision Model\n",
    "\n",
    "```python\n",
    "model_path = \"meta-llama/Llama-4-Scout-17B-16E-Instruct\"\n",
    "chat_template = \"llama-4\"\n",
    "\n",
    "from io import BytesIO\n",
    "import requests\n",
    "from PIL import Image\n",
    "\n",
    "from sglang.srt.parser.conversation import chat_templates\n",
    "\n",
    "# Download the same example image\n",
    "image = Image.open(BytesIO(requests.get(example_image_url).content))\n",
    "\n",
    "conv = chat_templates[chat_template].copy()\n",
    "conv.append_message(conv.roles[0], f\"What's shown here: {conv.image_token}?\")\n",
    "conv.append_message(conv.roles[1], \"\")\n",
    "conv.image_data = [image]\n",
    "\n",
    "print(\"Llama 4 generated prompt text:\")\n",
    "print(conv.get_prompt())\n",
    "print(f\"Image size: {image.size}\")\n",
    "\n",
    "image\n",
    "```"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "14",
   "metadata": {},
   "source": [
    "### Llama 4 Basic Call\n",
    "\n",
    "Llama 4 requires more computational resources, so it's configured with multi-GPU parallelism (tp_size=4) and larger context length.\n",
    "\n",
    "```python\n",
    "llm = Engine(\n",
    "    model_path=model_path,\n",
    "    enable_multimodal=True,\n",
    "    attention_backend=\"fa3\",\n",
    "    tp_size=4,\n",
    "    context_length=65536,\n",
    ")\n",
    "\n",
    "out = llm.generate(prompt=conv.get_prompt(), image_data=[image])\n",
    "print(\"Llama 4 response:\")\n",
    "print(out[\"text\"])\n",
    "```"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "15",
   "metadata": {},
   "source": [
    "### Call with Processor Output\n",
    "\n",
    "Using HuggingFace processor to preprocess data can reduce computational overhead during inference.\n",
    "\n",
    "```python\n",
    "from transformers import AutoProcessor\n",
    "\n",
    "processor = AutoProcessor.from_pretrained(model_path, use_fast=True)\n",
    "processor_output = processor(\n",
    "    images=[image], text=conv.get_prompt(), return_tensors=\"pt\"\n",
    ")\n",
    "\n",
    "out = llm.generate(\n",
    "    input_ids=processor_output[\"input_ids\"][0].detach().cpu().tolist(),\n",
    "    image_data=[dict(processor_output, format=\"processor_output\")],\n",
    ")\n",
    "print(\"Response using processor output:\")\n",
    "print(out)\n",
    "```"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "16",
   "metadata": {},
   "source": [
    "### Call with Precomputed Embeddings\n",
    "\n",
    "```python\n",
    "from transformers import AutoProcessor\n",
    "from transformers import Llama4ForConditionalGeneration\n",
    "\n",
    "processor = AutoProcessor.from_pretrained(model_path, use_fast=True)\n",
    "model = Llama4ForConditionalGeneration.from_pretrained(\n",
    "    model_path, torch_dtype=\"auto\"\n",
    ").eval()\n",
    "\n",
    "vision = model.vision_model.cuda()\n",
    "multi_modal_projector = model.multi_modal_projector.cuda()\n",
    "\n",
    "print(f'Image pixel values shape: {processor_output[\"pixel_values\"].shape}')\n",
    "input_ids = processor_output[\"input_ids\"][0].detach().cpu().tolist()\n",
    "\n",
    "# Process image through vision encoder\n",
    "image_outputs = vision(\n",
    "    processor_output[\"pixel_values\"].to(\"cuda\"), \n",
    "    aspect_ratio_ids=processor_output[\"aspect_ratio_ids\"].to(\"cuda\"),\n",
    "    aspect_ratio_mask=processor_output[\"aspect_ratio_mask\"].to(\"cuda\"),\n",
    "    output_hidden_states=False\n",
    ")\n",
    "image_features = image_outputs.last_hidden_state\n",
    "\n",
    "# Flatten image features and pass through multimodal projector\n",
    "vision_flat = image_features.view(-1, image_features.size(-1))\n",
    "precomputed_embeddings = multi_modal_projector(vision_flat)\n",
    "\n",
    "# Build precomputed embedding data item\n",
    "mm_item = dict(\n",
    "    processor_output, \n",
    "    format=\"precomputed_embedding\", \n",
    "    feature=precomputed_embeddings\n",
    ")\n",
    "\n",
    "# Use precomputed embeddings for efficient inference\n",
    "out = llm.generate(input_ids=input_ids, image_data=[mm_item])\n",
    "print(\"Llama 4 precomputed embedding response:\")\n",
    "print(out[\"text\"])\n",
    "```"
   ]
  }
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