"\n# Hello, NAS!\n\nThis is the 101 tutorial of Neural Architecture Search (NAS) on NNI.\nIn this tutorial, we will search for a neural architecture on MNIST dataset with the help of NAS framework of NNI, i.e., *Retiarii*.\nWe use multi-trial NAS as an example to show how to construct and explore a model space.\n\nThere are mainly three crucial components for a neural architecture search task, namely,\n\n* Model search space that defines a set of models to explore.\n* A proper strategy as the method to explore this model space.\n* A model evaluator that reports the performance of every model in the space.\n\nCurrently, PyTorch is the only supported framework by Retiarii, and we have only tested **PyTorch 1.7 to 1.10**.\nThis tutorial assumes PyTorch context but it should also apply to other frameworks, which is in our future plan.\n\n## Define your Model Space\n\nModel space is defined by users to express a set of models that users want to explore, which contains potentially good-performing models.\nIn this framework, a model space is defined with two parts: a base model and possible mutations on the base model.\n"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Define Base Model\n\nDefining a base model is almost the same as defining a PyTorch (or TensorFlow) model.\nUsually, you only need to replace the code ``import torch.nn as nn`` with\n``import nni.retiarii.nn.pytorch as nn`` to use our wrapped PyTorch modules.\n\nBelow is a very simple example of defining a base model.\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"import torch\nimport torch.nn.functional as F\nimport nni.retiarii.nn.pytorch as nn\nfrom nni.retiarii import model_wrapper\n\n\n@model_wrapper # this decorator should be put on the out most\nclass Net(nn.Module):\n def __init__(self):\n super().__init__()\n self.conv1 = nn.Conv2d(1, 32, 3, 1)\n self.conv2 = nn.Conv2d(32, 64, 3, 1)\n self.dropout1 = nn.Dropout(0.25)\n self.dropout2 = nn.Dropout(0.5)\n self.fc1 = nn.Linear(9216, 128)\n self.fc2 = nn.Linear(128, 10)\n\n def forward(self, x):\n x = F.relu(self.conv1(x))\n x = F.max_pool2d(self.conv2(x), 2)\n x = torch.flatten(self.dropout1(x), 1)\n x = self.fc2(self.dropout2(F.relu(self.fc1(x))))\n output = F.log_softmax(x, dim=1)\n return output"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
".. tip:: Always keep in mind that you should use ``import nni.retiarii.nn.pytorch as nn`` and :meth:`nni.retiarii.model_wrapper`.\n Many mistakes are a result of forgetting one of those.\n Also, please use ``torch.nn`` for submodules of ``nn.init``, e.g., ``torch.nn.init`` instead of ``nn.init``.\n\n### Define Model Mutations\n\nA base model is only one concrete model not a model space. We provide :doc:`API and Primitives </nas/construct_space>`\nfor users to express how the base model can be mutated. That is, to build a model space which includes many models.\n\nBased on the above base model, we can define a model space as below.\n\n.. code-block:: diff\n\n @model_wrapper\n class Net(nn.Module):\n def __init__(self):\n super().__init__()\n self.conv1 = nn.Conv2d(1, 32, 3, 1)\n - self.conv2 = nn.Conv2d(32, 64, 3, 1)\n + self.conv2 = nn.LayerChoice([\n + nn.Conv2d(32, 64, 3, 1),\n + DepthwiseSeparableConv(32, 64)\n + ])\n - self.dropout1 = nn.Dropout(0.25)\n + self.dropout1 = nn.Dropout(nn.ValueChoice([0.25, 0.5, 0.75]))\n self.dropout2 = nn.Dropout(0.5)\n - self.fc1 = nn.Linear(9216, 128)\n - self.fc2 = nn.Linear(128, 10)\n + feature = nn.ValueChoice([64, 128, 256])\n + self.fc1 = nn.Linear(9216, feature)\n + self.fc2 = nn.Linear(feature, 10)\n\n def forward(self, x):\n x = F.relu(self.conv1(x))\n x = F.max_pool2d(self.conv2(x), 2)\n x = torch.flatten(self.dropout1(x), 1)\n x = self.fc2(self.dropout2(F.relu(self.fc1(x))))\n output = F.log_softmax(x, dim=1)\n return output\n\nThis results in the following code:\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"class DepthwiseSeparableConv(nn.Module):\n def __init__(self, in_ch, out_ch):\n super().__init__()\n self.depthwise = nn.Conv2d(in_ch, in_ch, kernel_size=3, groups=in_ch)\n self.pointwise = nn.Conv2d(in_ch, out_ch, kernel_size=1)\n\n def forward(self, x):\n return self.pointwise(self.depthwise(x))\n\n\n@model_wrapper\nclass ModelSpace(nn.Module):\n def __init__(self):\n super().__init__()\n self.conv1 = nn.Conv2d(1, 32, 3, 1)\n # LayerChoice is used to select a layer between Conv2d and DwConv.\n self.conv2 = nn.LayerChoice([\n nn.Conv2d(32, 64, 3, 1),\n DepthwiseSeparableConv(32, 64)\n ])\n # ValueChoice is used to select a dropout rate.\n # ValueChoice can be used as parameter of modules wrapped in `nni.retiarii.nn.pytorch`\n # or customized modules wrapped with `@basic_unit`.\n self.dropout1 = nn.Dropout(nn.ValueChoice([0.25, 0.5, 0.75])) # choose dropout rate from 0.25, 0.5 and 0.75\n self.dropout2 = nn.Dropout(0.5)\n feature = nn.ValueChoice([64, 128, 256])\n self.fc1 = nn.Linear(9216, feature)\n self.fc2 = nn.Linear(feature, 10)\n\n def forward(self, x):\n x = F.relu(self.conv1(x))\n x = F.max_pool2d(self.conv2(x), 2)\n x = torch.flatten(self.dropout1(x), 1)\n x = self.fc2(self.dropout2(F.relu(self.fc1(x))))\n output = F.log_softmax(x, dim=1)\n return output\n\n\nmodel_space = ModelSpace()\nmodel_space"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"This example uses two mutation APIs, ``nn.LayerChoice`` and ``nn.ValueChoice``.\n``nn.LayerChoice`` takes a list of candidate modules (two in this example), one will be chosen for each sampled model.\nIt can be used like normal PyTorch module.\n``nn.ValueChoice`` takes a list of candidate values, one will be chosen to take effect for each sampled model.\n\nMore detailed API description and usage can be found :doc:`here </nas/construct_space>`.\n\n<div class=\"alert alert-info\"><h4>Note</h4><p>We are actively enriching the mutation APIs, to facilitate easy construction of model space.\n If the currently supported mutation APIs cannot express your model space,\n please refer to :doc:`this doc </nas/mutator>` for customizing mutators.</p></div>\n\n## Explore the Defined Model Space\n\nThere are basically two exploration approaches: (1) search by evaluating each sampled model independently,\nwhich is the search approach in `multi-trial NAS <multi-trial-nas>`\nand (2) one-shot weight-sharing based search, which is used in one-shot NAS.\nWe demonstrate the first approach in this tutorial. Users can refer to `here <one-shot-nas>` for the second approach.\n\nFirst, users need to pick a proper exploration strategy to explore the defined model space.\nSecond, users need to pick or customize a model evaluator to evaluate the performance of each explored model.\n\n### Pick an exploration strategy\n\nRetiarii supports many :doc:`exploration strategies </nas/exploration_strategy>`.\n\nSimply choosing (i.e., instantiate) an exploration strategy as below.\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"import nni.retiarii.strategy as strategy\nsearch_strategy = strategy.Random(dedup=True) # dedup=False if deduplication is not wanted"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Pick or customize a model evaluator\n\nIn the exploration process, the exploration strategy repeatedly generates new models. A model evaluator is for training\nand validating each generated model to obtain the model's performance.\nThe performance is sent to the exploration strategy for the strategy to generate better models.\n\nRetiarii has provided :doc:`built-in model evaluators </nas/evaluator>`, but to start with,\nit is recommended to use ``FunctionalEvaluator``, that is, to wrap your own training and evaluation code with one single function.\nThis function should receive one single model class and uses ``nni.report_final_result`` to report the final score of this model.\n\nAn example here creates a simple evaluator that runs on MNIST dataset, trains for 2 epochs, and reports its validation accuracy.\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"import nni\n\nfrom torchvision import transforms\nfrom torchvision.datasets import MNIST\nfrom torch.utils.data import DataLoader\n\n\ndef train_epoch(model, device, train_loader, optimizer, epoch):\n loss_fn = torch.nn.CrossEntropyLoss()\n model.train()\n for batch_idx, (data, target) in enumerate(train_loader):\n data, target = data.to(device), target.to(device)\n optimizer.zero_grad()\n output = model(data)\n loss = loss_fn(output, target)\n loss.backward()\n optimizer.step()\n if batch_idx % 10 == 0:\n print('Train Epoch: {} [{}/{} ({:.0f}%)]\\tLoss: {:.6f}'.format(\n epoch, batch_idx * len(data), len(train_loader.dataset),\n 100. * batch_idx / len(train_loader), loss.item()))\n\n\ndef test_epoch(model, device, test_loader):\n model.eval()\n test_loss = 0\n correct = 0\n with torch.no_grad():\n for data, target in test_loader:\n data, target = data.to(device), target.to(device)\n output = model(data)\n pred = output.argmax(dim=1, keepdim=True)\n correct += pred.eq(target.view_as(pred)).sum().item()\n\n test_loss /= len(test_loader.dataset)\n accuracy = 100. * correct / len(test_loader.dataset)\n\n print('\\nTest set: Accuracy: {}/{} ({:.0f}%)\\n'.format(\n correct, len(test_loader.dataset), accuracy))\n\n return accuracy\n\n\ndef evaluate_model(model_cls):\n # \"model_cls\" is a class, need to instantiate\n model = model_cls()\n\n device = torch.device('cuda') if torch.cuda.is_available() else torch.device('cpu')\n model.to(device)\n\n optimizer = torch.optim.Adam(model.parameters(), lr=1e-3)\n transf = transforms.Compose([transforms.ToTensor(), transforms.Normalize((0.1307,), (0.3081,))])\n train_loader = DataLoader(MNIST('data/mnist', download=True, transform=transf), batch_size=64, shuffle=True)\n test_loader = DataLoader(MNIST('data/mnist', download=True, train=False, transform=transf), batch_size=64)\n\n for epoch in range(3):\n # train the model for one epoch\n train_epoch(model, device, train_loader, optimizer, epoch)\n # test the model for one epoch\n accuracy = test_epoch(model, device, test_loader)\n # call report intermediate result. Result can be float or dict\n nni.report_intermediate_result(accuracy)\n\n # report final test result\n nni.report_final_result(accuracy)"
"The ``train_epoch`` and ``test_epoch`` here can be any customized function, where users can write their own training recipe.\n\nIt is recommended that the :doc:``evaluate_model`` here accepts no additional arguments other than ``model_cls``.\nHowever, in the `advanced tutorial </nas/evaluator>`, we will show how to use additional arguments in case you actually need those.\nIn future, we will support mutation on the arguments of evaluators, which is commonly called \"Hyper-parmeter tuning\".\n\n## Launch an Experiment\n\nAfter all the above are prepared, it is time to start an experiment to do the model search. An example is shown below.\n\n"
"The following configurations are useful to control how many trials to run at most / at the same time.\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"exp_config.max_trial_number = 4 # spawn 4 trials at most\nexp_config.trial_concurrency = 2 # will run two trials concurrently"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Remember to set the following config if you want to GPU.\n``use_active_gpu`` should be set true if you wish to use an occupied GPU (possibly running a GUI).\n\n"
"Launch the experiment. The experiment should take several minutes to finish on a workstation with 2 GPUs.\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"exp.run(exp_config, 8081)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Users can also run Retiarii Experiment with :doc:`different training services </experiment/training_service>`\nbesides ``local`` training service.\n\n## Visualize the Experiment\n\nUsers can visualize their experiment in the same way as visualizing a normal hyper-parameter tuning experiment.\nFor example, open ``localhost:8081`` in your browser, 8081 is the port that you set in ``exp.run``.\nPlease refer to :doc:`here </experiment/webui>` for details.\n\nWe support visualizing models with 3rd-party visualization engines (like `Netron <https://netron.app/>`__).\nThis can be used by clicking ``Visualization`` in detail panel for each trial.\nNote that current visualization is based on `onnx <https://onnx.ai/>`__ ,\nthus visualization is not feasible if the model cannot be exported into onnx.\n\nBuilt-in evaluators (e.g., Classification) will automatically export the model into a file.\nFor your own evaluator, you need to save your file into ``$NNI_OUTPUT_DIR/model.onnx`` to make this work.\nFor instance,\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"import os\nfrom pathlib import Path\n\n\ndef evaluate_model_with_visualization(model_cls):\n model = model_cls()\n # dump the model into an onnx\n if 'NNI_OUTPUT_DIR' in os.environ:\n dummy_input = torch.zeros(1, 3, 32, 32)\n torch.onnx.export(model, (dummy_input, ),\n Path(os.environ['NNI_OUTPUT_DIR']) / 'model.onnx')\n evaluate_model(model_cls)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Relaunch the experiment, and a button is shown on WebUI.\n\n<img src=\"file://../../img/netron_entrance_webui.png\">\n\n## Export Top Models\n\nUsers can export top models after the exploration is done using ``export_top_models``.\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"for model_dict in exp.export_top_models(formatter='dict'):\n print(model_dict)\n\n# The output is `json` object which records the mutation actions of the top model.\n# If users want to output source code of the top model, they can use graph-based execution engine for the experiment,\n# by simply adding the following two lines.\n#\n# .. code-block:: python\n#\n# exp_config.execution_engine = 'base'\n# export_formatter = 'code'"
The following configurations are useful to control how many trials to run at most / at the same time.
.. GENERATED FROM PYTHON SOURCE LINES 289-293
.. code-block:: default
exp_config.max_trial_number = 4 # spawn 4 trials at most
exp_config.trial_concurrency = 2 # will run two trials concurrently
.. GENERATED FROM PYTHON SOURCE LINES 294-296
Remember to set the following config if you want to GPU.
``use_active_gpu`` should be set true if you wish to use an occupied GPU (possibly running a GUI).
.. GENERATED FROM PYTHON SOURCE LINES 296-300
.. code-block:: default
exp_config.trial_gpu_number = 1
exp_config.training_service.use_active_gpu = True
.. GENERATED FROM PYTHON SOURCE LINES 301-302
Launch the experiment. The experiment should take several minutes to finish on a workstation with 2 GPUs.
.. GENERATED FROM PYTHON SOURCE LINES 302-305
.. code-block:: default
exp.run(exp_config, 8081)
.. rst-class:: sphx-glr-script-out
Out:
.. code-block:: none
[2022-02-28 14:01:13] INFO (nni.experiment/MainThread) Creating experiment, Experiment ID: dt84p16a
[2022-02-28 14:01:13] INFO (nni.experiment/MainThread) Connecting IPC pipe...
[2022-02-28 14:01:14] INFO (nni.experiment/MainThread) Starting web server...
[2022-02-28 14:01:15] INFO (nni.experiment/MainThread) Setting up...
[2022-02-28 14:01:15] INFO (nni.runtime.msg_dispatcher_base/Thread-3) Dispatcher started
[2022-02-28 14:01:15] INFO (nni.retiarii.experiment.pytorch/MainThread) Web UI URLs: http://127.0.0.1:8081 http://10.190.172.35:8081 http://192.168.49.1:8081 http://172.17.0.1:8081
[2022-02-28 14:01:15] INFO (nni.retiarii.experiment.pytorch/MainThread) Start strategy...
[2022-02-28 14:01:15] INFO (root/MainThread) Successfully update searchSpace.
[2022-02-28 14:01:15] INFO (nni.retiarii.strategy.bruteforce/MainThread) Random search running in fixed size mode. Dedup: on.
[2022-02-28 14:05:16] INFO (nni.retiarii.experiment.pytorch/Thread-4) Stopping experiment, please wait...
[2022-02-28 14:05:16] INFO (nni.retiarii.experiment.pytorch/MainThread) Strategy exit
[2022-02-28 14:05:16] INFO (nni.retiarii.experiment.pytorch/MainThread) Waiting for experiment to become DONE (you can ctrl+c if there is no running trial jobs)...
[2022-02-28 14:05:17] INFO (nni.runtime.msg_dispatcher_base/Thread-3) Dispatcher exiting...
[2022-02-28 14:05:17] INFO (nni.retiarii.experiment.pytorch/Thread-4) Experiment stopped
.. GENERATED FROM PYTHON SOURCE LINES 306-324
Users can also run Retiarii Experiment with :doc:`different training services </experiment/training_service>`
besides ``local`` training service.
Visualize the Experiment
------------------------
Users can visualize their experiment in the same way as visualizing a normal hyper-parameter tuning experiment.
For example, open ``localhost:8081`` in your browser, 8081 is the port that you set in ``exp.run``.
Please refer to :doc:`here </experiment/webui>` for details.
We support visualizing models with 3rd-party visualization engines (like `Netron <https://netron.app/>`__).
This can be used by clicking ``Visualization`` in detail panel for each trial.
Note that current visualization is based on `onnx <https://onnx.ai/>`__ ,
thus visualization is not feasible if the model cannot be exported into onnx.
Built-in evaluators (e.g., Classification) will automatically export the model into a file.
For your own evaluator, you need to save your file into ``$NNI_OUTPUT_DIR/model.onnx`` to make this work.
"\n# NNI HPO Quickstart with PyTorch\nThis tutorial optimizes the model in `official PyTorch quickstart`_ with auto-tuning.\n\nThere is also a :doc:`TensorFlow version<../hpo_quickstart_tensorflow/main>` if you prefer it.\n\nThe tutorial consists of 4 steps: \n\n1. Modify the model for auto-tuning.\n2. Define hyperparameters' search space.\n3. Configure the experiment.\n4. Run the experiment.\n\n"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Step 1: Prepare the model\nIn first step, we need to prepare the model to be tuned.\n\nThe model should be put in a separate script.\nIt will be evaluated many times concurrently,\nand possibly will be trained on distributed platforms.\n\nIn this tutorial, the model is defined in :doc:`model.py <model>`.\n\nIn short, it is a PyTorch model with 3 additional API calls:\n\n1. Use :func:`nni.get_next_parameter` to fetch the hyperparameters to be evalutated.\n2. Use :func:`nni.report_intermediate_result` to report per-epoch accuracy metrics.\n3. Use :func:`nni.report_final_result` to report final accuracy.\n\nPlease understand the model code before continue to next step.\n\n"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Step 2: Define search space\nIn model code, we have prepared 3 hyperparameters to be tuned:\n*features*, *lr*, and *momentum*.\n\nHere we need to define their *search space* so the tuning algorithm can sample them in desired range.\n\nAssuming we have following prior knowledge for these hyperparameters:\n\n1. *features* should be one of 128, 256, 512, 1024.\n2. *lr* should be a float between 0.0001 and 0.1, and it follows exponential distribution.\n3. *momentum* should be a float between 0 and 1.\n\nIn NNI, the space of *features* is called ``choice``;\nthe space of *lr* is called ``loguniform``;\nand the space of *momentum* is called ``uniform``.\nYou may have noticed, these names are derived from ``numpy.random``.\n\nFor full specification of search space, check :doc:`the reference </hpo/search_space>`.\n\nNow we can define the search space as follow:\n\n"
"## Step 3: Configure the experiment\nNNI uses an *experiment* to manage the HPO process.\nThe *experiment config* defines how to train the models and how to explore the search space.\n\nIn this tutorial we use a *local* mode experiment,\nwhich means models will be trained on local machine, without using any special training platform.\n\n"
"Now we start to configure the experiment.\n\n### Configure trial code\nIn NNI evaluation of each hyperparameter set is called a *trial*.\nSo the model script is called *trial code*.\n\n"
"When ``trial_code_directory`` is a relative path, it relates to current working directory.\nTo run ``main.py`` in a different path, you can set trial code directory to ``Path(__file__).parent``.\n(`__file__ <https://docs.python.org/3.10/reference/datamodel.html#index-43>`__\nis only available in standard Python, not in Jupyter Notebook.)\n\n.. attention::\n\n If you are using Linux system without Conda,\n you may need to change ``\"python model.py\"`` to ``\"python3 model.py\"``.\n\n"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Configure search space\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"experiment.config.search_space = search_space"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"### Configure tuning algorithm\nHere we use :doc:`TPE tuner </hpo/tuners>`.\n\n"
"<div class=\"alert alert-info\"><h4>Note</h4><p>``max_trial_number`` is set to 10 here for a fast example.\n In real world it should be set to a larger number.\n With default config TPE tuner requires 20 trials to warm up.</p></div>\n\nYou may also set ``max_experiment_duration = '1h'`` to limit running time.\n\nIf neither ``max_trial_number`` nor ``max_experiment_duration`` are set,\nthe experiment will run forever until you press Ctrl-C.\n\n"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Step 4: Run the experiment\nNow the experiment is ready. Choose a port and launch it. (Here we use port 8080.)\n\nYou can use the web portal to view experiment status: http://localhost:8080.\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"experiment.run(8080)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## After the experiment is done\nEverything is done and it is safe to exit now. The following are optional.\n\nIf you are using standard Python instead of Jupyter Notebook,\nyou can add ``input()`` or ``signal.pause()`` to prevent Python from exiting,\nallowing you to view the web portal after the experiment is done.\n\n"
]
},
{
"cell_type": "code",
"execution_count": null,
"metadata": {
"collapsed": false
},
"outputs": [],
"source": [
"# input('Press enter to quit')\nexperiment.stop()"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
":meth:`nni.experiment.Experiment.stop` is automatically invoked when Python exits,\nso it can be omitted in your code.\n\nAfter the experiment is stopped, you can run :meth:`nni.experiment.Experiment.view` to restart web portal.\n\n.. tip::\n\n This example uses :doc:`Python API </reference/experiment>` to create experiment.\n\n You can also create and manage experiments with :doc:`command line tool </reference/nnictl>`.\n\n"
"\n# Port PyTorch Quickstart to NNI\nThis is a modified version of `PyTorch quickstart`_.\n\nIt can be run directly and will have the exact same result as original version.\n\nFurthermore, it enables the ability of auto tuning with an NNI *experiment*, which will be detailed later.\n\nIt is recommended to run this script directly first to verify the environment.\n\nThere are 2 key differences from the original version:\n\n1. In `Get optimized hyperparameters`_ part, it receives generated hyperparameters.\n2. In `Train model and report accuracy`_ part, it reports accuracy metrics to NNI.\n\n"
"## Get optimized hyperparameters\nIf run directly, :func:`nni.get_next_parameter` is a no-op and returns an empty dict.\nBut with an NNI *experiment*, it will receive optimized hyperparameters from tuning algorithm.\n\n"
