Log

Applicability

Product	Supported
Atlas 350 Accelerator Card	√
Atlas A3 training product/Atlas A3 inference product	x
Atlas A2 training product/Atlas A2 inference product	x
Atlas 200I/500 A2 inference product	x
Atlas inference product AI Core	x
Atlas inference product Vector Core	x
Atlas training product	x

Function Usage

Computes the natural logarithm of the input data srcReg based on mask and writes the result to dstReg. The formula is as follows:

$\text{[math]}$

Prototype

template <typename T = DefaultType, auto mode = MaskMergeMode::ZEROING, typename U>
__simd_callee__ inline void Log(U& dstReg, U& srcReg, MaskReg& mask)

Parameters

**Table 1** Parameters in the template
Parameter	Description
T	Operand data type. For the Atlas 350 Accelerator Card, the supported data types are half and float.
mode	It can be set to the enumeration of MaskMergeMode or a pointer to a structure of LogSpecificMode. MaskMergeMode: Set it to MERGING or ZEROING. ZEROING: The elements that are not filtered by mask are set to zero in dstReg. MERGING: This option is not supported currently. LogSpecificMode is defined as follows: enum class LogAlgo { INTRINSIC = 0, PRECISION_1ULP_FTZ_TRUE, PRECISION_1ULP_FTZ_FALSE, }; struct LogSpecificMode{ MaskMergeMode mrgMode = MaskMergeMode::ZEROING, LogAlgo algo = LogAlgo::INTRINSIC; }; mrgMode: Set it to MERGING or ZEROING. algo: used to configure the subnormal mode. LogAlgo::INTRINSIC and LogAlgo::PRECISION_1ULP_FTZ_TRUE: The result is computed using a single instruction, and all subnormal numbers are approximated to 0. LogAlgo::PRECISION_1ULP_FTZ_FALSE: Subnormal data computation is supported.
U	RegTensor type of the source and destination operands, for example, RegTensor<half>. It is automatically inferred by the compiler and does not need to be specified.

**Table 2** Parameters
Parameter	Input/Output	Description
dstReg	Output	Destination operand. The type is RegTensor.
srcReg	Input	Source operand. The type is RegTensor. The source operand must have the same data type as the destination operand.
mask	Input	Valid indication of the source operand element operation. For details, see MaskReg.

Returns

None

Restrictions

When the input src is -0, the output is -inf.

Examples

template<typename T>
__simd_vf__ inline void LogVF(__ubuf__ T* dstAddr, __ubuf__ T* srcAddr, uint32_t count, 
 uint32_t oneRepeatSize, uint16_t repeatTimes)
{
    AscendC::Reg::RegTensor<T> srcReg;
    AscendC::Reg::RegTensor<T> dstReg;
    AscendC::Reg::MaskReg mask;
    // Subnormal mode
    // static constexpr AscendC::Reg::LogSpecificMode mode = {MaskMergeMode::ZEROING, LogAlgo::PRECISION_1ULP_FTZ_FALSE};
    for (uint16_t i = 0; i < repeatTimes; i++) {     
        mask = AscendC::Reg::UpdateMask<T>(count);
        AscendC::Reg::LoadAlign(srcReg, srcAddr + i * oneRepeatSize);
        AscendC::Reg::Log(dstReg, srcReg, mask);
        // Subnormal mode
        // AscendC::Reg::Log<DTYPE, &mode>(dstReg, srcReg, mask);
        AscendC::Reg::StoreAlign(dstAddr + i * oneRepeatSize, dstReg, mask);
    }
}

Parent topic: Basic Arithmetic