openvino/docs/ops/normalization/MVN_6.md

# MVN {#openvino_docs_ops_normalization_MVN_6}

**Versioned name**: *MVN-6*

**Category**: *Normalization*

**Short description**: Calculates mean-variance normalization of the input tensor.

**Detailed description**

*MVN* subtracts mean value from the input blob:
\f[
o_{i} = i_{i} - ReduceMean(i_{k}, axes)
\f]

If *normalize_variance* is set to `true`, the output blob is divided by variance. When normalizing the value, the number `eps` is added to the variance to avoid division by zero. According to the `eps_mode` flag's value, `eps` is added inside or outside the sqrt:

* If `eps_mode` is `inside_sqrt`:
\f[
o_{i}=\frac{o_{i}}{\sqrt {\sum {o_{k}^2}+\epsilon}}
\f]
* If `eps_mode` is `outside_sqrt`:
\f[
o_{i}=\frac{o_{i}}{\sqrt {\sum {o_{k}^2}}+\epsilon}
\f]

**Attributes**

* *normalize_variance*

  * **Description**: *normalize_variance* is a flag that specifies whether to perform variance normalization.
  * **Range of values**:
    * `false` - do not normalize variance
    * `true` - normalize variance
  * **Type**: `boolean`
  * **Required**: *yes*

* *eps*

  * **Description**: *eps* is the number to be added to the variance to avoid division by zero when normalizing the value.
  * **Range of values**: a positive floating-point number
  * **Type**: `float`
  * **Required**: *yes*

* *eps_mode*

  * **Description**: Choose where to add epsilon.
  * **Range of values**:
    * `inside_sqrt` - add epsilon inside sqrt
    * `outside_sqrt` - add epsilon outside of sqrt
  * **Type**: `string`
  * **Required**: *yes*

**Inputs**

* **1**: `data` - Input tensor to be normalized of type *T* and arbitrary shape. **Required.**

* **2**: `axes` - 1D tensor which specifies indices of dimensions in `data` that define normalization slices. Allowed range of axes is `[-r; r-1]` where `r = rank(data)`, the order can be not sorted. Negative value means counting dimensions from the back. Type *T_IND*. **Required.**

**Outputs**

* **1**: Output tensor of the same shape and type as the `data` input tensor.

**Types**

* *T*: any floating point type.
* *T_IND*: `int64` or `int32`.

**Example**

```xml
<layer ... type="MVN">
    <data eps="1e-9" eps_mode="inside_sqrt" normalize_variance="true"/>
    <input>
        <port id="0">
            <dim>6</dim>
            <dim>12</dim>
            <dim>10</dim>
            <dim>24</dim>
        </port>
        <port id="1">
            <dim>3</dim>         <!-- value of [0,2,3] means independent normalization per channels -->
        </port>
    </input>
    <output>
        <port id="2">
            <dim>6</dim>
            <dim>12</dim>
            <dim>10</dim>
            <dim>24</dim>
        </port>
    </output>
</layer>
```