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96 lines
4.8 KiB
Markdown
96 lines
4.8 KiB
Markdown
---
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title: Freeway
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---
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# Freeway
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```{figure} ../../_static/videos/atari/freeway.gif
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:width: 120px
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:name: Freeway
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```
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This environment is part of the <a href='..'>Atari environments</a>. Please read that page first for general information.
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| Action Space | Discrete(3) |
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| Observation Shape | (210, 160, 3) |
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| Observation High | 255 |
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| Observation Low | 0 |
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| Import | `gymnasium.make("ALE/Freeway-v5")` |
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For more Freeway variants with different observation and action spaces, see the variants section.
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## Description
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your objective is to guide your chicken across lane after lane of busy rush hour traffic. You receive a point for every chicken that makes it to the top of the screen after crossing all the lanes of traffic.
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For a more detailed documentation, see [the AtariAge page](https://atariage.com/manual_thumbs.php?SoftwareLabelID=192)
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## Actions
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Freeway has the action space `Discrete(3)` with the table below lists the meaning of each action's meanings.
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As Freeway uses a reduced set of actions for `v0`, `v4` and `v5` versions of the environment.
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To enable all 18 possible actions that can be performed on an Atari 2600, specify `full_action_space=True` during
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initialization or by passing `full_action_space=True` to `gymnasium.make`.
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| Value | Meaning | Value | Meaning | Value | Meaning |
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|---------|-----------|---------|-----------|---------|-----------|
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| `0` | `NOOP` | `1` | `UP` | `2` | `DOWN` |
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## Observations
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Atari environment have two possible observation types, the observation space is listed below.
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See variants section for the type of observation used by each environment id.
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- `obs_type="rgb" -> observation_space=Box(0, 255, (210, 160, 3), np.uint8)`
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- `obs_type="ram" -> observation_space=Box(0, 255, (128,), np.uint8)`
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Additionally, `obs_type="grayscale"` cause the environment return a grayscale version of the rgb array for observations with the observation space being `Box(0, 255, (210, 160), np.uint8)`
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### Rewards
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The exact reward dynamics depend on the environment and are usually documented in the game's manual. You can
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find these manuals on [AtariAge](https://atariage.com/manual_thumbs.php?SoftwareLabelID=192).
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Atari environments are simulated via the Arcade Learning Environment (ALE) [[1]](#1).
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## Variants
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Freeway has the following variants of the environment id which have the following differences in observation,
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the number of frame-skips and the repeat action probability.
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| Env-id | obs_type= | frameskip= | repeat_action_probability= |
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|-----------------------------|-------------|--------------|------------------------------|
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| Freeway-v0 | `"rgb"` | `(2, 5)` | `0.25` |
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| Freeway-ram-v0 | `"ram"` | `(2, 5)` | `0.25` |
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| Freeway-ramDeterministic-v0 | `"ram"` | `4` | `0.25` |
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| Freeway-ramNoFrameskip-v0 | `"ram"` | `1` | `0.25` |
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| FreewayDeterministic-v0 | `"rgb"` | `4` | `0.25` |
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| FreewayNoFrameskip-v0 | `"rgb"` | `1` | `0.25` |
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| Freeway-v4 | `"rgb"` | `(2, 5)` | `0.0` |
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| Freeway-ram-v4 | `"ram"` | `(2, 5)` | `0.0` |
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| Freeway-ramDeterministic-v4 | `"ram"` | `4` | `0.0` |
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| Freeway-ramNoFrameskip-v4 | `"ram"` | `1` | `0.0` |
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| FreewayDeterministic-v4 | `"rgb"` | `4` | `0.0` |
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| FreewayNoFrameskip-v4 | `"rgb"` | `1` | `0.0` |
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| ALE/Freeway-v5 | `"rgb"` | `4` | `0.25` |
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| ALE/Freeway-ram-v5 | `"ram"` | `4` | `0.25` |
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## Difficulty and modes
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It is possible to specify various flavors of the environment via the keyword arguments `difficulty` and `mode`.
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A flavor is a combination of a game mode and a difficulty setting. The table below lists the possible difficulty and mode values
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along with the default values.
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| Available Modes | Default Mode | Available Difficulties | Default Difficulty |
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|-------------------|----------------|--------------------------|----------------------|
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| `[0, ..., 7]` | `0` | `[0, 1]` | `0` |
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## Version History
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A thorough discussion of the intricate differences between the versions and configurations can be found in the general article on Atari environments.
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* v5: Stickiness was added back and stochastic frameskipping was removed. The environments are now in the "ALE" namespace.
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* v4: Stickiness of actions was removed
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* v0: Initial versions release
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