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   "source": [
    "[![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/duoan/TorchCode/blob/master/templates/20_weight_init.ipynb)\n",
    "\n",
    "# 🟢 Easy: Kaiming Initialization\n",
    "\n",
    "Implement **Kaiming (He) normal initialization** for weight tensors.\n",
    "\n",
    "$$W \\sim \\mathcal{N}(0, \\text{std}^2) \\quad \\text{where} \\quad \\text{std} = \\sqrt{\\frac{2}{\\text{fan\\_in}}}$$\n",
    "\n",
    "### Signature\n",
    "```python\n",
    "def kaiming_init(weight: Tensor) -> Tensor:\n",
    "    # Initialize weight in-place with Kaiming normal\n",
    "    # fan_in = weight.shape[1]\n",
    "    # Returns the weight tensor\n",
    "```"
   ],
   "outputs": []
  },
  {
   "cell_type": "code",
   "metadata": {},
   "source": [
    "# Install torch-judge in Colab (no-op in JupyterLab/Docker)\n",
    "try:\n",
    "    import google.colab\n",
    "    get_ipython().run_line_magic('pip', 'install -q torch-judge')\n",
    "except ImportError:\n",
    "    pass\n"
   ],
   "outputs": [],
   "execution_count": null
  },
  {
   "cell_type": "code",
   "metadata": {},
   "outputs": [],
   "source": [
    "import torch\n",
    "import math"
   ],
   "execution_count": null
  },
  {
   "cell_type": "code",
   "metadata": {},
   "outputs": [],
   "source": [
    "# ✏️ YOUR IMPLEMENTATION HERE\n",
    "\n",
    "def kaiming_init(weight):\n",
    "    pass  # fill with normal(0, sqrt(2/fan_in))"
   ],
   "execution_count": null
  },
  {
   "cell_type": "code",
   "metadata": {},
   "outputs": [],
   "source": [
    "# 🧪 Debug\n",
    "import math\n",
    "w = torch.empty(256, 512)\n",
    "kaiming_init(w)\n",
    "print(f'Mean: {w.mean():.4f} (expect ~0)')\n",
    "print(f'Std:  {w.std():.4f} (expect {math.sqrt(2/512):.4f})')"
   ],
   "execution_count": null
  },
  {
   "cell_type": "code",
   "metadata": {},
   "outputs": [],
   "source": [
    "# ✅ SUBMIT\n",
    "from torch_judge import check\n",
    "check('weight_init')"
   ],
   "execution_count": null
  }
 ],
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