aie::linear_approx< T, MyLUT > Struct Template Reference

Detailed Description

template<typename T, ParallelLUT MyLUT>
struct aie::linear_approx< T, MyLUT >

Type to support a linear approximation via interpolation with slope/offset values stored in a lookup table.

The logical steps of the computation are:

• index = floor(input / step) + bias
• slope/offset pair read from LUT based on index
• output = slope * (input % step_bits) + (offset << shift_offset)

Supported linear approximation types

Input	Offset	Slope	Accumulator type
int8	int8	int8	acc32
int16	int16 int32	int16 int32	acc64
bfloat16	float	bfloat16	accfloat

Template Parameters

T	Type of the input vector, containing values used to index the lookup table.
MyLUT	Definition of the LUT type, using the lut type.

#include <aie.hpp>

Public Member Functions
	linear_approx (const MyLUT &l, unsigned step_bits, int bias=0, int shift_offset=0)
	More...
template<Vector Vec>
auto	compute (const Vec &input)
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Constructor & Destructor Documentation

linear_approx()

template<typename T , ParallelLUT MyLUT>

aie::linear_approx< T, MyLUT >::linear_approx ( const MyLUT &  l, unsigned  step_bits, int  bias = 0, int  shift_offset = 0  )

inline

Constructor, configures aspects of how the approximation is performed.

Parameters

l	LUT containing the stored slope/offset value pairs used for the linear approximation. Each value in the LUT has the slope in the LSB, the offset in the MSB.
step_bits	Lower bits that won't be used from the input to index the LUT, these will be the remainder multiplied by the slope value at each point.
bias	Optional offset added to the input values used to index, for example to center on 0 by adding half the number of LUT elements.
shift_offset	Optional scaling factor applied to the offset before adding it (to avoid loss of precision).

Member Function Documentation

compute()

template<typename T , ParallelLUT MyLUT>

template<Vector Vec>

auto aie::linear_approx< T, MyLUT >::compute ( const Vec &  input )

inline

Performs a linear approximation for the input values with the configured lookup table. An accumulator of the same number of elements as the input is returned.
Input values are interpreted from MSB to LSB: headroom | LUT elements | step_bits

Parameters

input

Vector of input values that are used to index the look-up table.

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The documentation for this struct was generated from the following file:

• aie.hpp