Gather

Versioned name: Gather-1

Category: Data movement

Short description: Gather operation takes slices of data in the first input tensor according to the indices specified in the second input tensor and axis from the third input.

Detailed description

output[p_0, p_1, ..., p_{axis-1}, i, ..., j, ...] =
  input1[p_0, p_1, ..., p_{axis-1}, input2[i, ..., j], ...]

Where axis is the value from the third input.

Attributes: Gather has no attributes

Inputs

• 1: Tensor with arbitrary data. Required.

• 2: Tensor with indices to gather. The values for indices are in the range [0, input1[axis] - 1]. Required.

• 3: Scalar or 1D tensor axis is a dimension index to gather data from. For example, axis equal to 1 means that gathering is performed over the first dimension. Negative value means reverse indexing. Allowed values are from [-len(input1.shape), len(input1.shape) - 1]. Required.

Outputs

• 1: The resulting tensor that consists of elements from the first input tensor gathered by indices from the second input tensor. Shape of the tensor is [input1.shape[:axis], input2.shape, input1.shape[axis + 1:]]

Example

<layer id="1" type="Gather" ...>
    <input>
        <port id="0">
            <dim>6</dim>
            <dim>12</dim>
            <dim>10</dim>
            <dim>24</dim>
        </port>
        <port id="1">
            <dim>15</dim>
            <dim>4</dim>
            <dim>20</dim>
            <dim>28</dim>
        </port>
        <port id="2"/>        <!--  axis = 1  -->
    </input>
    <output>
        <port id="2">
            <dim>6</dim>      <!-- embedded dimension from the 1st input -->
            <dim>15</dim>     <!-- embedded dimension from the 2nd input -->
            <dim>4</dim>      <!-- embedded dimension from the 2nd input -->
            <dim>20</dim>     <!-- embedded dimension from the 2nd input -->
            <dim>28</dim>     <!-- embedded dimension from the 2nd input -->
            <dim>10</dim>     <!-- embedded dimension from the 1st input -->
            <dim>24</dim>     <!-- embedded dimension from the 1st input -->
        </port>
    </output>
</layer>