Range¶

Versioned name: Range-4

Category: Generation

Short description: Range operation generates a sequence of numbers according input values [start, stop) with a step.

Attributes:

output_type
- Description: the output tensor type
- Range of values: any numeric type
- Type: string
- Required: yes

Inputs:

1: “start” - A scalar of type T1. Required.
2: “stop” - A scalar of type T2. Required.
3: “step” - A scalar of type T3. If step is equal to zero after casting to output_type, behavior is undefined. Required.

Outputs:

1: A tensor with type specified by attribute output_type.

Types

T1, T2, T3: any numeric type.

Detailed description:

Range operation generates a sequence of numbers starting from the value in the first input (start) up to but not including the value in the second input (stop) with a step equal to the value in the third input, according to the following formula:

For a positive step:

\[start<=val[i]<stop,\]

for a negative step:

\[start>=val[i]>stop,\]

the i-th element is calculated by the following formula:

\[val[i+1]=val[i]+step.\]

The calculations are done after casting all values to accumulate_type(output_type). accumulate_type is a type that have better or equal accuracy for accumulation than output_type on current hardware, e.g. fp64 for fp16. The number of elements is calculated in the floating-point type according to the following formula:

\[max(ceil((end − start) / step), 0)\]

This is aligned with PyTorch’s operation torch.arange, to align with tensorflow operation tf.range all inputs must be casted to output_type before calling Range. The rounding for casting values are done towards zero.

Examples

Example 1: positive step

 <layer ... type="Range">
     <data output_type="i32">
     <input>
         <port id="0">  < !-- start value: 2 -->
         </port>
         <port id="1">  < !-- stop value: 23 -->
         </port>
         <port id="2">  < !-- step value: 3 -->
         </port>
     </input>
     <output>
         <port id="3">
             <dim>7</dim> < !-- [ 2,  5,  8, 11, 14, 17, 20] -->
         </port>
     </output>
 </layer>

Example 2: negative step

 <layer ... type="Range">
     <data output_type="i32">
     <input>
         <port id="0">  < !-- start value: 23 -->
         </port>
         <port id="1">  < !-- stop value: 2 -->
         </port>
         <port id="2">  < !-- step value: -3 -->
         </port>
     </input>
     <output>
         <port id="3">
             <dim>7</dim> < !-- [23, 20, 17, 14, 11, 8, 5] -->
         </port>
     </output>
 </layer>

Example 3: floating-point

 <layer ... type="Range">
     <data output_type="f32">
     <input>
         <port id="0">  < !-- start value: 1 -->
         </port>
         <port id="1">  < !-- stop value: 2.5 -->
         </port>
         <port id="2">  < !-- step value: 0.5 -->
         </port>
     </input>
     <output>
         <port id="3">
             <dim>3</dim> < !-- [ 1.0,  1.5,  2.0] -->
         </port>
     </output>
 </layer>