Typically each trial job gets a single configuration (e.g., hyperparameters) from tuner, tries this configuration and reports result, then exits. But sometimes a trial job may wants to request multiple configurations from tuner. We find this is a very compelling feature. For example:
1. Job launch takes tens of seconds in some training platform. If a configuration takes only around a minute to finish, running only one configuration in a trial job would be very inefficient. An appealing way is that a trial job requests a configuration and finishes it, then requests another configuration and run. The extreme case is that a trial job can run infinite configurations. If you set concurrency to be for example 6, there would be 6 __long running__ jobs keeping trying different configurations.
2. Some types of models have to be trained phase by phase, the configuration of next phase depends on the results of previous phase(s). For example, to find the best quantization for a model, the training procedure is often as follows: the auto-quantization algorithm (i.e., tuner in NNI) chooses a size of bits (e.g., 16 bits), a trial job gets this configuration and trains the model for some epochs and reports result (e.g., accuracy). The algorithm receives this result and makes decision of changing 16 bits to 8 bits, or changing back to 32 bits. This process is repeated for a configured times.
The above cases can be supported by the same feature, i.e., multi-phase execution. To support those cases, basically a trial job should be able to request multiple configurations from tuner. Tuner is aware of whether two configuration requests are from the same trial job or different ones. Also in multi-phase a trial job can report multiple final results.
## Create multi-phase experiment
### Write trial code which leverages multi-phase:
__1. Update trial code__
It is pretty simple to use multi-phase in trial code, an example is shown below:
```python
# ...
foriinrange(5):
# get parameter from tuner
tuner_param=nni.get_next_parameter()
# nni.get_next_parameter returns None if there is no more hyper parameters can be generated by tuner.
iftuner_paramisNone:
break
# consume the params
# ...
# report final result somewhere for the parameter retrieved above
nni.report_final_result()
# ...
# ...
```
In multi-phase experiments, at each time the API `nni.get_next_parameter()` is called, it returns a new hyper parameter generated by tuner, then the trail code consume this new hyper parameter and report final result of this hyper parameter. `nni.get_next_parameter()` and `nni.report_final_result()` should be called sequentially: __call the former one, then call the later one; and repeat this pattern__. If `nni.get_next_parameter()` is called multiple times consecutively, and then `nni.report_final_result()` is called once, the result is associated to the last configuration, which is retrieved from the last get_next_parameter call. So there is no result associated to previous get_next_parameter calls, and it may cause some multi-phase algorithm broken.
Note that, `nni.get_next_parameter` returns None if there is no more hyper parameters can be generated by tuner.
__2. Experiment configuration__
To enable multi-phase, you should also add `multiPhase: true` in your experiment YAML configure file. If this line is not added, `nni.get_next_parameter()` would always return the same configuration.
Multi-phase experiment configuration example:
```yaml
authorName:default
experimentName:multiphase experiment
trialConcurrency:2
maxExecDuration:1h
maxTrialNum:8
trainingServicePlatform:local
searchSpacePath:search_space.json
multiPhase:true
useAnnotation:false
tuner:
builtinTunerName:TPE
classArgs:
optimize_mode:maximize
trial:
command:python3 mytrial.py
codeDir:.
gpuNum:0
```
### Write a tuner that leverages multi-phase:
Before writing a multi-phase tuner, we highly suggest you to go through [Customize Tuner](https://nni.readthedocs.io/en/latest/Tuner/CustomizeTuner.html). Same as writing a normal tuner, your tuner needs to inherit from `Tuner` class. When you enable multi-phase through configuration (set `multiPhase` to true), your tuner will get an additional parameter `trial_job_id` via tuner's following methods:
```text
generate_parameters
generate_multiple_parameters
receive_trial_result
receive_customized_trial_result
trial_end
```
With this information, the tuner could know which trial is requesting a configuration, and which trial is reporting results. This information provides enough flexibility for your tuner to deal with different trials and different phases. For example, you may want to use the trial_job_id parameter of generate_parameters method to generate hyperparameters for a specific trial job.
@@ -26,7 +26,7 @@ NNI supports running experiment using [FrameworkController](https://github.com/M
## Setup FrameworkController
Follow the [guideline](https://github.com/Microsoft/frameworkcontroller/tree/master/example/run) to set up FrameworkController in the Kubernetes cluster, NNI supports FrameworkController by the stateful set mode.
Follow the [guideline](https://github.com/Microsoft/frameworkcontroller/tree/master/example/run) to set up FrameworkController in the Kubernetes cluster, NNI supports FrameworkController by the stateful set mode. If your cluster enforces authorization, you need to create a service account with granted permission for FrameworkController, and then pass the name of the FrameworkController service account to the NNI Experiment Config. [refer](https://github.com/Microsoft/frameworkcontroller/tree/master/example/run#run-by-kubernetes-statefulset)
## Design
...
...
@@ -83,6 +83,7 @@ If you use Azure Kubernetes Service, you should set `frameworkcontrollerConfig`
Random search is suggested when each trial does not take very long (e.g., each trial can be completed very quickly, or early stopped by the assessor), and you have enough computational resources. It's also useful if you want to uniformly explore the search space. Random Search can be considered a baseline search algorithm. [Detailed Description](./HyperoptTuner.md)
**classArgs Requirements:**
***optimize_mode** (*maximize or minimize, optional, default = maximize*) - If 'maximize', the tuner will try to maximize metrics. If 'minimize', the tuner will try to minimize metrics.
`receive_trial_result` will receive the `parameter_id, parameters, value` as parameters input. Also, Tuner will receive the `value` object are exactly same value that Trial send. If `multiPhase` is set to `true` in the experiment configuration file, an additional `trial_job_id` parameter is passed to `receive_trial_result` and `generate_parameters` through the `**kwargs` parameter.
`receive_trial_result` will receive the `parameter_id, parameters, value` as parameters input. Also, Tuner will receive the `value` object are exactly same value that Trial send.
The `your_parameters` return from `generate_parameters` function, will be package as json object by NNI SDK. NNI SDK will unpack json object so the Trial will receive the exact same `your_parameters` from Tuner.
...
...
@@ -109,4 +109,4 @@ More detail example you could see:
### Write a more advanced automl algorithm
The methods above are usually enough to write a general tuner. However, users may also want more methods, for example, intermediate results, trials' state (e.g., the methods in assessor), in order to have a more powerful automl algorithm. Therefore, we have another concept called `advisor` which directly inherits from `MsgDispatcherBase` in [`src/sdk/pynni/nni/msg_dispatcher_base.py`](https://github.com/Microsoft/nni/tree/master/src/sdk/pynni/nni/msg_dispatcher_base.py). Please refer to [here](CustomizeAdvisor.md) for how to write a customized advisor.
\ No newline at end of file
The methods above are usually enough to write a general tuner. However, users may also want more methods, for example, intermediate results, trials' state (e.g., the methods in assessor), in order to have a more powerful automl algorithm. Therefore, we have another concept called `advisor` which directly inherits from `MsgDispatcherBase` in [`src/sdk/pynni/nni/msg_dispatcher_base.py`](https://github.com/Microsoft/nni/tree/master/src/sdk/pynni/nni/msg_dispatcher_base.py). Please refer to [here](CustomizeAdvisor.md) for how to write a customized advisor.
@@ -67,10 +67,8 @@ It doesn't need to redeploy, but the nnictl may need to be restarted.
#### TypeScript
* If `src/nni_manager` will be changed, run `yarn watch` continually under this folder. It will rebuild code instantly.
* If `src/webui` or `src/nasui` is changed, use **step 3** to rebuild code.
The nnictl may need to be restarted.
* If `src/nni_manager` is changed, run `yarn watch` continually under this folder. It will rebuild code instantly. The nnictl may need to be restarted to reload NNI manager.
* If `src/webui` or `src/nasui` are changed, run `yarn start` under the corresponding folder. The web UI will refresh automatically if code is changed.
