* [docs] buffer_size parameter clarification
It was not fully clear that it has a different behavior for PPO and SAC. The docs update should improve the understanding.
* [docs] updated buffer_size parameter clarification
Co-authored-by: Vincent-Pierre BERGES <vincentpierre@unity3d.com>
Co-authored-by: Vincent-Pierre BERGES <vincentpierre@unity3d.com>
| `threaded` | (default = `true`) By default, model updates can happen while the environment is being stepped. This violates the [on-policy](https://spinningup.openai.com/en/latest/user/algorithms.html#the-on-policy-algorithms) assumption of PPO slightly in exchange for a training speedup. To maintain the strict on-policyness of PPO, you can disable parallel updates by setting `threaded` to `false`. There is usually no reason to turn `threaded` off for SAC. |
| `hyperparameters -> learning_rate` | (default = `3e-4`) Initial learning rate for gradient descent. Corresponds to the strength of each gradient descent update step. This should typically be decreased if training is unstable, and the reward does not consistently increase. <br><br>Typical range: `1e-5` - `1e-3` |
| `hyperparameters -> batch_size` | Number of experiences in each iteration of gradient descent. **This should always be multiple times smaller than `buffer_size`**. If you are using a continuous action space, this value should be large (in the order of 1000s). If you are using a discrete action space, this value should be smaller (in order of 10s). <br><br> Typical range: (Continuous - PPO): `512` - `5120`; (Continuous - SAC): `128` - `1024`; (Discrete, PPO & SAC): `32` - `512`. |
| `hyperparameters -> buffer_size` | (default = `10240` for PPO and `50000` for SAC) Number of experiences to collect before updating the policy model. Corresponds to how many experiences should be collected before we do any learning or updating of the model. **This should be multiple times larger than `batch_size`**. Typically a larger `buffer_size` corresponds to more stable training updates. In SAC, the max size of the experience buffer - on the order of thousands of times longer than your episodes, so that SAC can learn from old as well as new experiences. <br><br>Typical range: PPO: `2048` - `409600`; SAC: `50000` - `1000000` |
| `hyperparameters -> buffer_size` | (default = `10240` for PPO and `50000` for SAC)<br>**PPO:** Number of experiences to collect before updating the policy model. Corresponds to how many experiences should be collected before we do any learning or updating of the model. **This should be multiple times larger than `batch_size`**. Typically a larger `buffer_size` corresponds to more stable training updates. <br>**SAC:** The max size of the experience buffer - on the order of thousands of times longer than your episodes, so that SAC can learn from old as well as new experiences. <br><br>Typical range: PPO: `2048` - `409600`; SAC: `50000` - `1000000` |
| `hyperparameters -> learning_rate_schedule` | (default = `linear` for PPO and `constant` for SAC) Determines how learning rate changes over time. For PPO, we recommend decaying learning rate until max_steps so learning converges more stably. However, for some cases (e.g. training for an unknown amount of time) this feature can be disabled. For SAC, we recommend holding learning rate constant so that the agent can continue to learn until its Q function converges naturally. <br><br>`linear` decays the learning_rate linearly, reaching 0 at max_steps, while `constant` keeps the learning rate constant for the entire training run. |
| `network_settings -> hidden_units` | (default = `128`) Number of units in the hidden layers of the neural network. Correspond to how many units are in each fully connected layer of the neural network. For simple problems where the correct action is a straightforward combination of the observation inputs, this should be small. For problems where the action is a very complex interaction between the observation variables, this should be larger. <br><br> Typical range: `32` - `512` |
| `network_settings -> num_layers` | (default = `2`) The number of hidden layers in the neural network. Corresponds to how many hidden layers are present after the observation input, or after the CNN encoding of the visual observation. For simple problems, fewer layers are likely to train faster and more efficiently. More layers may be necessary for more complex control problems. <br><br> Typical range: `1` - `3` |
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