Sqrt

Applicability

Product

Supported

Atlas 350 Accelerator Card

Atlas A3 training product / Atlas A3 inference product

Atlas A2 training product / Atlas A2 inference product

Atlas 200I/500 A2 inference product

Atlas inference product AI Core

Atlas inference product Vector Core

x

Atlas training product

Function Usage

Computes the square root element-wise. The formula is as follows:

Prototype

  • Computation of the first n data elements of a tensor
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    constexpr SqrtConfig DEFAULT_SQRT_CONFIG = { SqrtAlgo::INTRINSIC };
    template <typename T, const SqrtConfig& config = DEFAULT_SQRT_CONFIG>
    __aicore__ inline void Sqrt(const LocalTensor<T>& dst, const LocalTensor<T>& src, const int32_t& count)
    
  • High-dimensional tensor sharding computation
    • Bitwise mask mode
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      template <typename T, bool isSetMask = true, const SqrtConfig& config = DEFAULT_SQRT_CONFIG>
      __aicore__ inline void Sqrt(const LocalTensor<T>& dst, const LocalTensor<T>& src, uint64_t mask[], const uint8_t repeatTime, const UnaryRepeatParams& repeatParams)
      
    • Contiguous mask mode
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      template <typename T, bool isSetMask = true, const SqrtConfig& config = DEFAULT_SQRT_CONFIG>
      __aicore__ inline void Sqrt(const LocalTensor<T>& dst, const LocalTensor<T>& src, uint64_t mask, const uint8_t repeatTime, const UnaryRepeatParams& repeatParams)
      

Parameters

Table 1 Template parameters

Parameter

Description

T

Operand data type.

For the Atlas training product , the supported data types are half and float.

For the Atlas inference product AI Core, the supported data types are half and float.

For the Atlas A2 training product / Atlas A2 inference product , the supported data types are half and float.

For the Atlas A3 training product / Atlas A3 inference product , the supported data types are half and float.

For the Atlas 200I/500 A2 inference product , the supported data types are half and float.

For the Atlas 350 Accelerator Card, the supported data types are half and float.

isSetMask

Indicates whether to set mask inside the API.

  • true: sets mask inside the API.
  • false: sets mask outside the API. Developers need to use the SetVectorMask API to set the mask value. In this mode, the mask value in the input parameter of this API must be set to the placeholder MASK_PLACEHOLDER.

config

This parameter is supported only by the Atlas 350 Accelerator Card.

Precision computation mode. The SqrtConfig type is defined as follows:

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enum class SqrtAlgo {
    INTRINSIC = 0,
    FAST_INVERSE,
    PRECISION_1ULP_FTZ_TRUE,
    PRECISION_0ULP_FTZ_FALSE,
    PRECISION_1ULP_FTZ_FALSE,
};
struct SqrtConfig {
    SqrtAlgo algo = SqrtAlgo::INTRINSIC;
};

The precision computation mode is configured by using the algo parameter of the SqrtConfig structure.

The options of algo are as follows:

  • SqrtAlgo::INTRINSIC and SqrtAlgo::PRECISION_1ULP_FTZ_TRUE: The result is computed using a single instruction, with a maximum precision error of 1 ulp.
  • SqrtAlgo::FAST_INVERSE and SqrtAlgo::PRECISION_0ULP_FTZ_FALSE: The result is computed using a fast inverse algorithm. This algorithm is applicable when the input value is within the range [0, 85070596800837026223494223584045301760]. Within this range, the algorithm guarantees a maximum precision error of 0 ulp for the output. When the input value exceeds 85070596800837026223494223584045301760, the output is 0. Currently, this algorithm supports only the float data type and supports subnormal data computation in this mode.
  • SqrtAlgo::PRECISION_1ULP_FTZ_FALSE: Only subnormal data computation of the half type is supported. In this case, the maximum precision error is 1 ulp.
Table 2 Parameters

Parameter

Input/Output

Description

dst

Output

Destination operand.

The type is LocalTensor, and TPosition can be VECIN, VECCALC, or VECOUT.

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

src

Input

Source operand.

The type is LocalTensor, and TPosition can be VECIN, VECCALC, or VECOUT.

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

The source operand must have the same data type as the destination operand.

count

Input

Number of elements involved in the computation.

mask[]/mask

Input

mask controls the elements that participate in computation in each iteration.

  • 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 from the computation.

    The mask value is an array. The array length and the value range of the array elements are related to the operand data type. When the operand is 16-bit, the array length is 2, with mask[0] and mask[1] each in the range [0, 264 – 1], and they cannot both be 0 at the same time. When the operand is 32-bit, the array length is 1, with mask[0] in the range (0, 264 – 1]. When the operand is 64-bit, the array length is 1, with mask[0] in the range (0, 232 – 1].

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

  • 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].

repeatTime

Input

Number of iteration repeats. The vector compute unit reads 256 bytes of contiguous data for computation each time. To process the input data, the data needs to be read and computed over multiple repeats. repeatTime indicates the number of repeats.

For details about this parameter, see High-dimensional Sharding APIs.

repeatParams

Input

Parameters that control the operand address strides. They are of the UnaryRepeatParams type (see UnaryRepeatParams), and contain parameters such as the address stride of the operand for the same Data Block between adjacent iterations and the address stride of the operand between different Data Blocks in a single iteration.

For details about the address stride of the operand between adjacent iterations, see repeatStride. For details about the address stride of the operand between different data blocks in a single iteration, see dataBlockStride.

Returns

None

Restrictions

  • If the value of src is not positive, unpredictable results may occur.

Examples

In the examples, both srcLocal and dstLocal are of half type.

For more examples, see LINK.

  • Example of high-dimensional tensor sharding computation (contiguous mask mode)
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    uint64_t mask = 256 / sizeof(half);
    // repeatTime = 4, 128 elements one repeat, 512 elements total
    // dstBlkStride, srcBlkStride = 1, no gap between blocks in one repeat
    // dstRepStride, srcRepStride = 8, no gap between repeats
    AscendC::Sqrt(dstLocal, srcLocal, mask, 4, { 1, 1, 8, 8 });
    
  • Example of high-dimensional tensor sharding computation (bitwise mask mode)
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    uint64_t mask[2] = { UINT64_MAX, UINT64_MAX };
    // repeatTime = 4, 128 elements one repeat, 512 elements total
    // dstBlkStride, srcBlkStride = 1, no gap between blocks in one repeat
    // dstRepStride, srcRepStride = 8, no gap between repeats
    AscendC::Sqrt(dstLocal, srcLocal, mask, 4, { 1, 1, 8, 8 });
    
  • Example of computing the first n data elements of a tensor
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    AscendC::Sqrt(dstLocal, srcLocal, 512);
    // Sqrt 0ulp
    static constexpr SqrtConfig config = { SqrtAlgo::FAST_INVERSE };
    Sqrt<T, config>(dstLocal, srcLocal, 512);
    // Sqrt Subnormal
    static constexpr SqrtConfig config = { SqrtAlgo::PRECISION_0ULP_FTZ_FALSE };
    Sqrt<T, config>(dstLocal, srcLocal, 512);
    
Result example:
Input (srcLocal): [1.0 2.0 3.0 4.0 ...]
Output (dstLocal): [1.0 1.414 1.732 2.0...]