# tf.keras.losses.MeanSquaredError

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| [![](https://www.tensorflow.org/images/GitHub-Mark-32px.png) View source on GitHub](https://github.com/keras-team/keras/tree/v2.13.1/keras/losses.py#L302-L358) |

Computes the mean of squares of errors between labels and predictions.

Inherits From: [`Loss`](https://www.tensorflow.org/versions/r2.13/api_docs/python/tf/keras/losses/Loss)

#### View aliases


**Main aliases**

[`tf.losses.MeanSquaredError`](https://www.tensorflow.org/api_docs/python/tf/keras/losses/MeanSquaredError)
**Compat aliases for migration**

See
[Migration guide](https://www.tensorflow.org/guide/migrate) for
more details.

\`tf.compat.v1.keras.losses.MeanSquaredError\`

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    tf.keras.losses.MeanSquaredError(
        reduction=losses_utils.ReductionV2.AUTO,
        name='mean_squared_error'
    )

`loss = mean(square(y_true - y_pred))`

#### Standalone usage:

    y_true = [[0., 1.], [0., 0.]]
    y_pred = [[1., 1.], [1., 0.]]
    # Using 'auto'/'sum_over_batch_size' reduction type.
    mse = tf.keras.losses.MeanSquaredError()
    mse(y_true, y_pred).numpy()
    0.5

    # Calling with 'sample_weight'.
    mse(y_true, y_pred, sample_weight=[0.7, 0.3]).numpy()
    0.25

    # Using 'sum' reduction type.
    mse = tf.keras.losses.MeanSquaredError(
        reduction=tf.keras.losses.Reduction.SUM)
    mse(y_true, y_pred).numpy()
    1.0

    # Using 'none' reduction type.
    mse = tf.keras.losses.MeanSquaredError(
        reduction=tf.keras.losses.Reduction.NONE)
    mse(y_true, y_pred).numpy()
    array([0.5, 0.5], dtype=float32)

Usage with the `compile()` API:

    model.compile(optimizer='sgd', loss=tf.keras.losses.MeanSquaredError())

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| ## Args ||
|---|---|
| `reduction` | Type of [`tf.keras.losses.Reduction`](https://www.tensorflow.org/versions/r2.13/api_docs/python/tf/keras/losses/Reduction) to apply to loss. Default value is `AUTO`. `AUTO` indicates that the reduction option will be determined by the usage context. For almost all cases this defaults to `SUM_OVER_BATCH_SIZE`. When used under a [`tf.distribute.Strategy`](https://www.tensorflow.org/versions/r2.13/api_docs/python/tf/distribute/Strategy), except via [`Model.compile()`](https://www.tensorflow.org/versions/r2.13/api_docs/python/tf/keras/Model#compile) and [`Model.fit()`](https://www.tensorflow.org/versions/r2.13/api_docs/python/tf/keras/Model#fit), using `AUTO` or `SUM_OVER_BATCH_SIZE` will raise an error. Please see this custom training [tutorial](https://www.tensorflow.org/tutorials/distribute/custom_training) for more details. |
| `name` | Optional name for the instance. Defaults to 'mean_squared_error'. |

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## Methods

### `from_config`

[View source](https://github.com/keras-team/keras/tree/v2.13.1/keras/losses.py#L285-L299)

    @classmethod
    from_config(
        config
    )

Instantiates a `Loss` from its config (output of `get_config()`).

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| Args ||
|---|---|
| `config` | Output of `get_config()`. |

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| Returns ||
|---|---|
| A [`keras.losses.Loss`](https://www.tensorflow.org/versions/r2.13/api_docs/python/tf/keras/losses/Loss) instance. ||

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### `get_config`

[View source](https://github.com/keras-team/keras/tree/v2.13.1/keras/losses.py#L270-L283)

    get_config()

Returns the config dictionary for a `Loss` instance.

### `__call__`

[View source](https://github.com/keras-team/keras/tree/v2.13.1/keras/losses.py#L101-L162)

    __call__(
        y_true, y_pred, sample_weight=None
    )

Invokes the `Loss` instance.

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| Args ||
|---|---|
| `y_true` | Ground truth values. shape = `[batch_size, d0, .. dN]`, except sparse loss functions such as sparse categorical crossentropy where shape = `[batch_size, d0, .. dN-1]` |
| `y_pred` | The predicted values. shape = `[batch_size, d0, .. dN]` |
| `sample_weight` | Optional `sample_weight` acts as a coefficient for the loss. If a scalar is provided, then the loss is simply scaled by the given value. If `sample_weight` is a tensor of size `[batch_size]`, then the total loss 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 loss element of `y_pred` is scaled by the corresponding value of `sample_weight`. (Note on`dN-1`: all loss functions reduce by 1 dimension, usually axis=-1.) |

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| Returns ||
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| Weighted loss float `Tensor`. If `reduction` is `NONE`, this has shape `[batch_size, d0, .. dN-1]`; otherwise, it is scalar. (Note `dN-1` because all loss functions reduce by 1 dimension, usually axis=-1.) ||

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| Raises ||
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| `ValueError` | If the shape of `sample_weight` is invalid. |

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