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feat: rename logit_bias/logit_scale to logit_mean/logit_sigma for affine score calibration (#39530)

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Signed-off-by: Jesus Federico <jefp@amazon.com>
Signed-off-by: wang.yuqi <yuqi.wang@daocloud.io>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: wang.yuqi <yuqi.wang@daocloud.io>
This commit is contained in:
Jesus Federico
2026-04-13 04:43:44 +00:00
committed by GitHub
co-authored by Claude Opus 4.6 wang.yuqi
parent 2a3c32ce67
commit fa6ae31177
7 changed files with 86 additions and 35 deletions
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docs/models/pooling_models/classify.md
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@@ -273,27 +273,25 @@ Affine Score Calibration, also known as [Platt Scaling](https://en.wikipedia.org
The calibration follows the transformation:
`activation(logit_scale * (logit - logit_bias))`
`activation((logit - logit_mean) / logit_sigma)`
| Parameter | Default | Description |
| --------- | ------- | ----------- |
| `logit_bias` | `None` | Bias subtracted from logits before activation |
| `logit_scale` | `None` | Scale factor applied to logits after bias subtraction |
Note: `logit_bias` is **subtracted** from the logits (not added), consistent with the `sigmoid_normalize` convention where `sigmoid(x - bias)` centers the sigmoid around the bias value.
| `logit_mean` | `None` | Mean subtracted from logits (centers scores) |
| `logit_sigma` | `None` | Standard deviation used to scale logits after mean subtraction |
The computation order is as follows:
```python
logits -= logit_bias # subtract bias (center scores)
logits *= logit_scale # scale logits
logits -= logit_mean # subtract mean (center scores)
logits /= logit_sigma # divide by sigma (scale)
logits = activation(logits) # e.g. sigmoid
```
Example configuration:
```bash
--pooler-config '{"use_activation": true, "logit_bias": 4.5, "logit_scale": 1.0}'
--pooler-config '{"use_activation": true, "logit_mean": 4.5, "logit_sigma": 1.0}'
```
## Removed Features
@@ -301,3 +299,7 @@ Example configuration:
### Remove softmax from PoolingParams
We have already removed `softmax` and `activation` from PoolingParams. Instead, use `use_activation`, since we allow `classify` and `token_classify` to use any activation function.
### Remove `logit_bias` and `logit_scale`
`logit_bias` and `logit_scale` are deprecated aliases for `logit_mean` and `logit_sigma` respectively. When using `logit_scale`, it is automatically converted to `logit_sigma = 1/logit_scale`. These deprecated parameters will be removed in v0.21.