Documentation

ShiftRight

Function Usage

Performs right shift on the source operand element-wise. The shift distance is determined by the scalar argument.

Performs logical right shift for the uint16_t/uint32_t data type while arithmetic right shift for the int16_t/int32_t data type.

By logical right shift, the least significant bit is discarded and the most significant bit is padded with 0.

By arithmetic right shift, the least significant bit is discarded and the sign bit is copied to the most significant bit.

For example, the 1-bit logical right shift of the uint16_t binary number 1010101010101010 is 0101010101010101.

The 1-bit arithmetic right shift of the int16_t binary number 1010101010101010 is 1101010101010101.

The 3-bit arithmetic right shift of the int16_t binary number 1010101010101010 is 1111010101010101.

Prototype

  • Computation of the first n data elements of a tensor 
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    template <typename T, bool isSetMask = true>
__aicore__ inline void ShiftRight(const LocalTensor<T>& dstLocal, const LocalTensor<T>& srcLocal, const T& scalarValue, const int32_t& calCount)
  • High-dimensional tensor sharding computation
    • Bitwise mask mode 
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      template <typename T, bool isSetMask = true>
__aicore__ inline void ShiftRight(const LocalTensor<T>& dstLocal, const LocalTensor<T>& srcLocal, const T& scalarValue, uint64_t mask[], const uint8_t repeatTimes, const UnaryRepeatParams& repeatParams, bool roundEn = false)
    • Contiguous mask mode 
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      template <typename T, bool isSetMask = true>
__aicore__ inline void ShiftRight(const LocalTensor<T>& dstLocal, const LocalTensor<T>& srcLocal, const T& scalarValue, uint64_t mask, const uint8_t repeatTimes, const UnaryRepeatParams& repeatParams, bool roundEn = false)

When dstLocal and srcLocal use the TensorTrait type, the data types of TensorTrait and scalarValue (corresponding to the LiteType type in TensorTrait) are different. Therefore, the new template type U indicates the data type of scalarValue, and std::enable_if is used to check whether LiteType extracted from T is the same as U. If they are the same, the API passes the compilation. Otherwise, the compilation fails. The API prototype is defined as follows:

  • Computation of the first n data elements of a tensor 
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    template <typename T, typename U, bool isSetMask = true, typename std::enable_if<IsSameType<PrimT<T>, U>::value, bool>::type = true>
__aicore__ inline void ShiftRight(const LocalTensor<T>& dstLocal, const LocalTensor<T>& srcLocal, const U& scalarValue, const int32_t& calCount)
  • High-dimensional tensor sharding computation
    • Bitwise mask mode 
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      template <typename T, typename U, bool isSetMask = true, typename std::enable_if<IsSameType<PrimT<T>, U>::value, bool>::type = true>
__aicore__ inline void ShiftRight(const LocalTensor<T>& dstLocal, const LocalTensor<T>& srcLocal, const U& scalarValue, uint64_t mask[], const uint8_t repeatTimes, const UnaryRepeatParams& repeatParams, bool roundEn)
    • Contiguous mask mode 
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      template <typename T, typename U, bool isSetMask = true, typename std::enable_if<IsSameType<PrimT<T>, U>::value, bool>::type = true>
__aicore__ inline void ShiftRight(const LocalTensor<T>& dstLocal, const LocalTensor<T>& srcLocal, const U& scalarValue, uint64_t mask, const uint8_t repeatTimes, const UnaryRepeatParams& repeatParams, bool roundEn)

Parameters

Table 1 Parameters in the template

Parameter

Description

T

Operand data type.

U

Data type of scalarValue.

isSetMask

Whether to set the mask mode and mask value inside the API.

  • true: indicates that the settings are performed inside the API.

    The APIs for high-dimensional tensor sharding computation and for calculating the first n pieces of data in a tensor use the normal mode and counter mode of the mask. Generally, retain the default value of isSetMask, indicating that the mask mode and mask value are set in the API based on the mask and calCount parameters passed by the developer.

  • false: indicates that the settings are performed outside the API.
Table 2 Parameters

Parameter

Input/Output

Meaning

dstLocal

Output

Destination operand.

The type is LocalTensor, and the supported TPosition is VECIN, VECCALC, or VECOUT.

The start address of the LocalTensor must be 32-byte aligned.

srcLocal

Input

Source operand.

The type is LocalTensor, and the supported TPosition is VECIN, VECCALC, or VECOUT.

The start address of the LocalTensor must be 32-byte aligned.

Its data type must be the same as that of the destination operand.

scalarValue

Input

Source operand, and its data type must be the same as that of the tensor element in the destination operand.

When src is of type uint16_t or int16_t, the scalar value range is [0, 16].

When src is of type uint32_t or int32_t, the scalar value range is [0, 32].

calCount

Input

Number of elements of the input data.

The parameter value range is related to the operand data type. The maximum number of elements that can be processed varies according to the data type.

The Vector Unit reads 256 bytes of contiguous data for computation each time. The unit needs to read and compute the input data in multiple repeats. Therefore, when the operand is of 16-bit, calCount ∈ [1, 128*255], where 255 indicates the maximum number of iterations, and 128 indicates that 128 pieces of 16-bit data can be processed in each iteration. When the operand is of 32-bit, calCount ∈ [1, 64*255], where 64 indicates that 64 pieces of 32-bit data can be processed in each iteration.

mask

Input

mask is used to control the elements that participate in computation in each iteration.

  • Contiguous mode: indicates the number of contiguous elements that participate in computation. The value range is related to the operand data type. The maximum number of elements that can be processed in each iteration varies according to the data type. When the operand is 16-bit, mask ∈ [1, 128]. When the operand is 32-bit, mask ∈ [1, 64]. When the operand is 64-bit, mask ∈ [1, 32].
  • Bitwise mode: controls the elements that participate in computation by bit. If a bit is set to 1, the corresponding element participates in the computation. If a bit is set to 0, the corresponding element is masked in the computation. The parameter type is a uint64_t array whose length is 2.

    For example, if mask = [0, 8] and 8 = 0b1000, only the fourth element participates in computation.

    The parameter value range is related to the operand data type. The maximum number of elements that can be processed in each iteration varies according to the data type. When the operand is 16-bit, mask[0] and mask[1] ∈ [0, 264 -1] and cannot be 0 at the same time. When the operand is 32-bit, mask[1] is 0 and mask[0] ∈ (0, 264 – 1]. When the operand is 64-bit, mask[1] is 0 and mask[0] ∈ (0, 232 – 1].

repeatTimes

Input

Number of iteration repeats. The Vector Unit reads 256 bytes of contiguous data for computation each time. To read the complete data for processing, the unit needs to read the input data in multiple repeats. repeatTimes indicates the number of iterations.

For details about this parameter, see Common Parameters.

repeatParams

Input

Control structure information of element operations. For details, see UnaryRepeatParams.

roundEn

Input

A bool. Set to True to enable the rounding function. Set to False to disable the rounding function. This parameter is valid only when src is of type int16_t or int32_t.

For example, with the rounding function enabled and src of type int16_t, the 5-bit arithmetic right shift of src is computed as follows:

src_ele = 17 = 0b0000000000010001 (the fifth bit is 1)

dst_ele = arithmetic_righ_shift(src_ele, 5) + 1

= 0b0000000000000000 + 1

= 0b0000000000000001

Returns

None

Availability

Precautions

  • To save memory space when using high-dimensional tensor sharding computation APIs, you can define a tensor shared by the source and destination operands (by address overlapping). The general instruction restrictions are as follows.
    • For a single repeat (repeatTimes = 1), the source operand must completely overlap the destination operand.
    • For multiple repeats (repeatTimes > 1), if there is a dependency between the source operand and the destination operand, that is, the destination operand of the Nth iteration is the source operand of the (N + 1)th iteration, address overlapping is not allowed.
  • For details about the alignment requirements of the operand address offset, see General Restrictions.

Example

This example shows only part of the code used in the computation process. If you need to run the sample code, copy the code snippet and replace the Compute function in the two-operand scalar instruction template provided in More Samples.
  • Example of high-dimensional tensor sharding computation (contiguous mask mode) 
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    uint64_t mask = 128;
int16_t scalar = 2;
// repeatTimes = 4. 128 elements are processed in a single iteration. To compute 512 elements, four iterations are required.
// dstBlkStride, srcBlkStride = 1. The interval between src0 data addresses involved in calculation in each iteration is one data block, indicating that data is continuously read and written in a single iteration.
// dstRepStride, srcRepStride = 8. The interval between addresses of adjacent iterations is eight data blocks, indicating that data is continuously read and written between adjacent iterations.
AscendC::ShiftRight(dstLocal, srcLocal, scalar, mask, 4, { 1, 1, 8, 8 }, false);
  • Example of high-dimensional tensor sharding computation (bitwise mask mode) 
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    uint64_t mask[2] = { UINT64_MAX, UINT64_MAX };
int16_t scalar = 2;
// repeatTimes = 4. 128 elements are processed in a single iteration. To compute 512 elements, four iterations are required.
// dstBlkStride, srcBlkStride = 1. The interval between src0 data addresses involved in calculation in each iteration is one data block, indicating that data is continuously read and written in a single iteration.
// dstRepStride, srcRepStride = 8. The interval between addresses of adjacent iterations is eight data blocks, indicating that data is continuously read and written between adjacent iterations.
AscendC::ShiftRight(dstLocal, srcLocal, scalar, mask, 4, {1, 1, 8, 8}, false);
  • Example of computing the first n data elements of a tensor 
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    int16_t scalar = 2;
AscendC::ShiftRight(dstLocal, srcLocal, scalar, 512);
Result example: 
Input (src0Local): [1 2 3 ... 512]
Input (scalar): 2
Output (dstLocal): [0 0 0 1 1 1 1 ... 128]