Slice

Versioned name: Slice-8

Category: Data movement

Short description: Slice operation extracts a slice of the input tensor.

Detailed Description: Slice operation selects a region of values from the data tensor. Selected values start at indexes provided in the start input (inclusively) and end at indexes provides in stop input (exclusively).

The step input allows subsampling of data, selecting every n-th element, where n is equal to step element for corresponding axis. Negative step value indicates slicing backwards, so the sequence along the corresponding axis is reversed in the output tensor. To select all values contiguously set step to 1 for each axis.

The optional axes input allows specifying slice indexes only on selected axes. Other axes will not be affected and will be output in full.

The rules follow python language slicing data[start:stop:step].

Attributes: Slice operation has no attributes.

Inputs

• 1: data - tensor (to be sliced) of type T and shape rank greater or equal to 1. Required.

• 2: start - 1D tensor of type T_IND. Indices corresponding to axes in data.

  Defines the starting coordinate of the slice in the data tensor. A negative index value represents counting elements from the end of that dimension. A value larger than the size of a dimension is silently clamped. Required.

• 3: stop - 1D, type T_IND, similar to start.

  Defines the coordinate of the opposite vertex of the slice, or where the slice ends. Stop indexes are exclusive, which means values lying on the ending edge are not included in the output slice. To slice to the end of a dimension of unknown size INT_MAX may be used (or INT_MIN if slicing backwards). Required.

• 4: step - 1D tensor of type T_IND and the same shape as start and stop.

  Integer value that specifies the increment between each index used in slicing. Value cannot be 0, negative value indicates slicing backwards. Required.

• 5: axes - 1D tensor of type T_AXIS.

  Optional 1D tensor indicating which dimensions the values in start and stop apply to. Negative value means counting dimensions from the end. The range is [-r, r - 1], where r is the rank of the data input tensor. Values are required to be unique. If a particular axis is unspecified, it will be output in full and not sliced. Default value: [0, 1, 2, ..., start.shape[0] - 1]. Optional.

Number of elements in start, stop, step, and axes inputs are required to be equal.

Outputs

• 1: Tensor of type T with values of the selected slice. The shape of the output tensor has the same rank as the shape of data input and reduced dimensions according to the values specified by start, stop, and step inputs.

Types

• T: any arbitrary supported type.

• T_IND: any supported integer type.

• T_AXIS: any supported integer type.

Examples

Example 1: basic slicing

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] -->
          <dim>10</dim>
        </port>
        <port id="1">       <!-- start: [1] -->
          <dim>1</dim>
        </port>
        <port id="2">       <!-- stop: [8] -->
          <dim>1</dim>
        </port>
        <port id="3">       <!-- step: [1] -->
          <dim>1</dim>
        </port>
        <port id="4">       <!-- axes: [0] -->
          <dim>1</dim>
        </port>
    </input>
    <output>
        <port id="5">       <!-- output: [1, 2, 3, 4, 5, 6, 7] -->
            <dim>7</dim>
        </port>
    </output>
</layer>

Example 2: basic slicing, axes default

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] -->
          <dim>10</dim>
        </port>
        <port id="1">       <!-- start: [1] -->
          <dim>1</dim>
        </port>
        <port id="2">       <!-- stop: [8] -->
          <dim>1</dim>
        </port>
        <port id="3">       <!-- step: [1] -->
          <dim>1</dim>
        </port>
    </input>
    <output>
        <port id="4">       <!-- output: [1, 2, 3, 4, 5, 6, 7] -->
            <dim>7</dim>
        </port>
    </output>
</layer>

Example 3: basic slicing, step: [2]

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] -->
          <dim>10</dim>
        </port>
        <port id="1">       <!-- start: [1] -->
          <dim>1</dim>
        </port>
        <port id="2">       <!-- stop: [8] -->
          <dim>1</dim>
        </port>
        <port id="3">       <!-- step: [2] -->
          <dim>1</dim>
        </port>
        <port id="4">       <!-- axes: [0] -->
          <dim>1</dim>
        </port>
    </input>
    <output>
        <port id="5">       <!-- output: [1, 3, 5, 7] -->
            <dim>4</dim>
        </port>
    </output>
</layer>

Example 4: start and stop out of the dimension size, step: [1]

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] -->
          <dim>10</dim>
        </port>
        <port id="1">       <!-- start: [-100] -->
          <dim>1</dim>
        </port>
        <port id="2">       <!-- stop: [100] -->
          <dim>1</dim>
        </port>
        <port id="3">       <!-- step: [1] -->
          <dim>1</dim>
        </port>
        <port id="4">       <!-- axes: [0] -->
          <dim>1</dim>
        </port>
    </input>
    <output>
        <port id="5">       <!-- output: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] -->
            <dim>10</dim>
        </port>
    </output>
</layer>

Example 5: slicing backward all elements, step: [-1], stop: [-11]

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] -->
          <dim>10</dim>
        </port>
        <port id="1">       <!-- start: [9] -->
          <dim>1</dim>
        </port>
        <port id="2">       <!-- stop: [-11] -->
          <dim>1</dim>
        </port>
        <port id="3">       <!-- step: [-1] -->
          <dim>1</dim>
        </port>
        <port id="4">       <!-- axes: [0] -->
          <dim>1</dim>
        </port>
    </input>
    <output>
        <port id="5">       <!-- output: [9, 8, 7, 6, 5, 4, 3, 2, 1, 0] -->
            <dim>10</dim>
        </port>
    </output>
</layer>

Example 6: slicing backward, step: [-1], stop: [0]

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] -->
          <dim>10</dim>
        </port>
        <port id="1">       <!-- start: [9] -->
          <dim>1</dim>
        </port>
        <port id="2">       <!-- stop: [0] -->
          <dim>1</dim>
        </port>
        <port id="3">       <!-- step: [-1] -->
          <dim>1</dim>
        </port>
        <port id="4">       <!-- axes: [0] -->
          <dim>1</dim>
        </port>
    </input>
    <output>
        <port id="5">       <!-- output: [9, 8, 7, 6, 5, 4, 3, 2, 1] -->
            <dim>9</dim>
        </port>
    </output>
</layer>

Example 7: slicing backward, step: [-1], stop: [-10]

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] -->
          <dim>10</dim>
        </port>
        <port id="1">       <!-- start: [9] -->
          <dim>1</dim>
        </port>
        <port id="2">       <!-- stop: [-10] -->
          <dim>1</dim>
        </port>
        <port id="3">       <!-- step: [-1] -->
          <dim>1</dim>
        </port>
        <port id="4">       <!-- axes: [0] -->
          <dim>1</dim>
        </port>
    </input>
    <output>
        <port id="5">       <!-- output: [9, 8, 7, 6, 5, 4, 3, 2, 1] -->
            <dim>9</dim>
        </port>
    </output>
</layer>

Example 8: slicing backward, step: [-2]

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] -->
          <dim>10</dim>
        </port>
        <port id="1">       <!-- start: [9] -->
          <dim>1</dim>
        </port>
        <port id="2">       <!-- stop: [-11] -->
          <dim>1</dim>
        </port>
        <port id="3">       <!-- step: [-2] -->
          <dim>1</dim>
        </port>
        <port id="4">       <!-- axes: [0] -->
          <dim>1</dim>
        </port>
    </input>
    <output>
        <port id="5">       <!-- output: [9, 7, 5, 3, 1] -->
            <dim>5</dim>
        </port>
    </output>
</layer>

Example 9: start and stop out of the dimension size, slicing backward

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] -->
          <dim>10</dim>
        </port>
        <port id="1">       <!-- start: [100] -->
          <dim>1</dim>
        </port>
        <port id="2">       <!-- stop: [-100] -->
          <dim>1</dim>
        </port>
        <port id="3">       <!-- step: [-1] -->
          <dim>1</dim>
        </port>
        <port id="4">       <!-- axes: [0] -->
          <dim>1</dim>
        </port>
    </input>
    <output>
        <port id="5">       <!-- output: [9, 8, 7, 6, 5, 4, 3, 2, 1, 0] -->
            <dim>10</dim>
        </port>
    </output>
</layer>

Example 10: slicing 2D tensor, all axes specified

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data: data: [[0, 1, 2, 3, 4], [5, 6, 7, 8, 9]] -->
          <dim>2</dim>
          <dim>5</dim>
        </port>
        <port id="1">       <!-- start: [0, 1] -->
          <dim>2</dim>
        </port>
        <port id="2">       <!-- stop: [2, 4] -->
          <dim>2</dim>
        </port>
        <port id="3">       <!-- step: [1, 2] -->
          <dim>2</dim>
        </port>
        <port id="4">       <!-- axes: [0, 1] -->
          <dim>2</dim>
        </port>
    </input>
    <output>
        <port id="5">      <!-- output: [1, 3, 6, 8] -->
            <dim>2</dim>
            <dim>2</dim>
        </port>
    </output>
</layer>

Example 11: slicing 3D tensor, all axes specified

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data -->
          <dim>20</dim>
          <dim>10</dim>
          <dim>5</dim>
        </port>
        <port id="1">       <!-- start: [0, 0, 0] -->
          <dim>2</dim>
        </port>
        <port id="2">       <!-- stop: [4, 10, 5] -->
          <dim>2</dim>
        </port>
        <port id="3">       <!-- step: [1, 1, 1] -->
          <dim>2</dim>
        </port>
        <port id="4">       <!-- axes: [0, 1, 2] -->
          <dim>2</dim>
        </port>
    </input>
    <output>
        <port id="5">       <!-- output -->
            <dim>4</dim>
            <dim>10</dim>
            <dim>5</dim>
        </port>
    </output>
</layer>

Example 12: slicing 3D tensor, last axes default

<layer id="1" type="Slice" ...>
    <input>
        <port id="0">       <!-- data -->
          <dim>20</dim>
          <dim>10</dim>
          <dim>5</dim>
        </port>
        <port id="1">       <!-- start: [0, 0] -->
          <dim>2</dim>
        </port>
        <port id="2">       <!-- stop: [4, 10] -->
          <dim>2</dim>
        </port>
        <port id="3">       <!-- step: [1, 1] -->
          <dim>2</dim>
        </port>
        <port id="4">       <!-- axes: [0, 1] -->
          <dim>2</dim>
        </port>
    </input>
    <output>
        <port id="5">       <!-- output -->
            <dim>4</dim>
            <dim>10</dim>
            <dim>5</dim>
        </port>
    </output>
</layer>