Vector and Accumulator Conversions

Overview

Vectors can be reinterpreted as vectors with a different element type, as long as they have the same total size.

aie::vector<int16, 32> v;
aie::vector<int32, 16> v2;
aie::vector<cint16, 16> v3;
 
v2 = v.cast_to<int32>(v);
 
v3 = aie::vector_cast<cint16>(v);

Vectors can be converted into accumulators. Their values can be shifted into a larger magnitude to implement fixed point precision schemes (this does not apply to floating point accumulators).

aie::vector<int16, 16> v;
aie::accum<acc32, 16> acc;
 
acc.from_vector(v, shift);

Conversely, accumulators can be converted into vectors. Their values can be shifted down before rounding and saturation is applied (this does not apply to floating point accumulators).

aie::accum<acc32, 16> acc;
aie::vector<int16, 16> v;
 
v = acc.to_vector<int16>(shift);

Functions
template<AccumElemBaseType AccumTag, VectorOrOp Vec>
accum< AccumTag, Vec::size()>	aie::from_vector (const Vec &v, int shift=0)
	Returns the values of the passed vector in an accumulator of the requested type after applying the requested upshift operation.
template<VectorOrOp Vec, typename T2 = Utils::get_prev_integer_type_t<typename Vec::value_type>> requires (!detail::is_floating_point_v<Vec>)
auto	aie::pack (const Vec &v) -> vector< T2, Vec::size()>
	Returns a conversion of the passed vector to the next smaller integer datatype, with the same number of elements.
template<typename TR, typename T> requires (AccumOrOp<T> || MmulOrOp<T>)
vector< TR, T::size()>	aie::to_vector (const T &acc, int shift=0)
	Returns the values of the passed accumulator in a vector of the requested type.
template<VectorOrOp Vec, typename T2 = Utils::get_next_integer_type_t<typename Vec::value_type>> requires (!detail::is_floating_point_v<Vec>)
auto	aie::unpack (const Vec &v) -> vector< T2, Vec::size()>
	Returns a conversion of the passed vector to the next larger integer datatype, with the same number of elements.
template<ElemBaseType DstT, Accum Acc> requires (arch::is(arch::Gen2))
auto	aie::vector_cast (const Acc &acc)
	Reinterpret an accumulator as a vector.
template<ElemBaseType DstT, Vector Vec>
auto	aie::vector_cast (const Vec &v)
	Reinterpret a vector using a different element type.

Function Documentation

from_vector()

template<AccumElemBaseType AccumTag, VectorOrOp Vec>

accum< AccumTag, Vec::size()> aie::from_vector	(	const Vec &	v,
		int	shift = 0 )

Returns the values of the passed vector in an accumulator of the requested type after applying the requested upshift operation.

Parameters

v	Input vector. The type must meet aie::VectorOrOp.
shift	Optional upshift in bits to be applied to output accumulator. This parameter is ignored for floating-point types.

Template Parameters

AccumTag

Accumulator tag that specifies returned accumulator type. The class must be compatible with the vector type (real/complex).

pack()

template<VectorOrOp Vec, typename T2 = Utils::get_prev_integer_type_t<typename Vec::value_type>>
requires (!detail::is_floating_point_v<Vec>)

auto aie::pack

(

const Vec &

v

)

-> vector<T2, Vec::size()>

Returns a conversion of the passed vector to the next smaller integer datatype, with the same number of elements.

Parameters

v	Input vector. The type must meet aie::VectorOrOp

Template Parameters

T2	Element type for the returned vector. Can only select between int8/uint8 on AIE1.

to_vector()

template<typename TR, typename T>
requires (AccumOrOp<T> || MmulOrOp<T>)

vector< TR, T::size()> aie::to_vector	(	const T &	acc,
		int	shift = 0 )

Returns the values of the passed accumulator in a vector of the requested type.

The values can be shifted down before rounding and saturation are applied (does not apply to floating point accumulators).

Note

On AIE-ML/XDNA 1 shift values of -4, -3, and -2 are unsafe, as they will only produce correct result if truncation is selected or saturation against 0 is required.

Parameters

acc	Input accumulator. The type must meet aie::AccumOrOp or aie::MmulOrOp.
shift	Optional downshift in bits to be applied to output data. This parameter is ignored for floating-point types.

Template Parameters

TR	Element type for the returned vector.

unpack()

template<VectorOrOp Vec, typename T2 = Utils::get_next_integer_type_t<typename Vec::value_type>>
requires (!detail::is_floating_point_v<Vec>)

auto aie::unpack

(

const Vec &

v

)

-> vector<T2, Vec::size()>

Returns a conversion of the passed vector to the next larger integer datatype, with the same number of elements.

Parameters

v	Input vector. The type must meet aie::VectorOrOp

vector_cast() [1/2]

template<ElemBaseType DstT, Accum Acc>
requires (arch::is(arch::Gen2))

auto aie::vector_cast

(

const Acc &

acc

)

Reinterpret an accumulator as a vector.

The returned vector has the same size in bits as the input accumulator.

Template Parameters

DstT	Element type for the returned vector.

Parameters

acc	Input accumulator.

vector_cast() [2/2]

template<ElemBaseType DstT, Vector Vec>

auto aie::vector_cast

(

const Vec &

v

)

Reinterpret a vector using a different element type.

The returned vector has the same size in bits as the input vector.

Template Parameters

DstT	Element type for the returned vector.

Parameters

v	Input vector.