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# tf.keras.metrics.KLDivergence

Computes Kullback-Leibler divergence metric between `y_true` and `y_pred`.

`metric = y_true * log(y_true / y_pred)`

#### Usage:

````m = tf.keras.metrics.KLDivergence()`
`_ = m.update_state([[0, 1], [0, 0]], [[0.6, 0.4], [0.4, 0.6]])`
`m.result().numpy()`
`0.45814306`
```
````m.reset_states()`
`_ = m.update_state([[0, 1], [0, 0]], [[0.6, 0.4], [0.4, 0.6]],`
`                   sample_weight=[1, 0])`
`m.result().numpy()`
`0.9162892`
```

Usage with tf.keras API:

``````model = tf.keras.Model(inputs, outputs)
model.compile('sgd', loss='mse', metrics=[tf.keras.metrics.KLDivergence()])
``````

`fn` The metric function to wrap, with signature `fn(y_true, y_pred, **kwargs)`.
`name` (Optional) string name of the metric instance.
`dtype` (Optional) data type of the metric result.
`**kwargs` The keyword arguments that are passed on to `fn`.

## Methods

### `reset_states`

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Resets all of the metric state variables.

This function is called between epochs/steps, when a metric is evaluated during training.

### `result`

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Computes and returns the metric value tensor.

Result computation is an idempotent operation that simply calculates the metric value using the state variables.

### `update_state`

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Accumulates metric statistics.

`y_true` and `y_pred` should have the same shape.

Args
`y_true` Ground truth values. shape = `[batch_size, d0, .. dN]`.
`y_pred` The predicted values. shape = `[batch_size, d0, .. dN]`.
`sample_weight` Optional `sample_weight` acts as a coefficient for the metric. If a scalar is provided, then the metric is simply scaled by the given value. If `sample_weight` is a tensor of size `[batch_size]`, then the metric for each sample of the batch is rescaled by the corresponding element in the `sample_weight` vector. If the shape of `sample_weight` is `[batch_size, d0, .. dN-1]` (or can be broadcasted to this shape), then each metric element of `y_pred` is scaled by the corresponding value of `sample_weight`. (Note on `dN-1`: all metric functions reduce by 1 dimension, usually the last axis (-1)).

Returns
Update op.

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