ShiftLeft (Shift Amount as Tensor)

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

Performs a left shift on each element of the source operand. A left shift operation is classified into the following types based on the data type of the source operand:

If the data type is unsigned, a logical left shift is performed. In this case, a left shift moves a binary number to the left by the specified number of bits, discarding the highest bits and filling the lowest bits with zeros. For example, the binary number 1010101010101010 (uint16_t) after a logical left shift by 1 bit becomes 0101010101010100.
If the data type is signed, an arithmetic left shift is performed. In this case, a left shift moves the binary number to the left by a specified number of bits, discarding the next most significant bits and filling the least significant bits with zeros. For example, the binary number 1010101010101010 (int16_t) becomes 1101010101010100 after an arithmetic left shift by 1 bit, and becomes 1101010101010000 after an arithmetic left shift by 3 bits.

Prototype

template <typename T, typename U>
__aicore__ inline void ShiftLeft(const LocalTensor<T>& dst, const LocalTensor<T>& src0, const LocalTensor<U>& src1, const int32_t& count)

Parameters

**Table 1** Template parameters
Parameter	Description
T	Data type of the source and destination operands. For the Atlas 350 Accelerator Card, the supported data types are int8_t, uint8_t, int16_t, uint16_t, int32_t, uint32_t, int64_t, and uint64_t.
U	Data type of the source operand. For the Atlas 350 Accelerator Card, the supported data types are int8_t, int16_t, int32_t, and int64_t.

**Table 2** Parameters
Parameter	Input/Output	Meaning
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.
src0	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 data type must be the same as that of the destination operand.
src1	Input	LocalTensor that stores the number of bits to shift (shift amount). It must have a data type with the same byte size as the tensor element data type of the src0 operand. Negative values are not supported.
count	Input	Number of elements involved in the computation.

Returns

None

Restrictions

For details about the operand address alignment requirements, see General Address Alignment Restrictions.

For a logical shift (unsigned data type), if the shift amount is greater than the bit width of the data type, the output is 0.
For an arithmetic shift (signed data type), if both src0 and src1 are less than 0 and the shift amount is greater than the bit width of the data type, the output is –1. If src0 is greater than 0 and the shift amount is greater than the bit width of the data type, the output is 0.

Examples

AscendC::ShiftLeft(dstLocal, srcLocal0, srcLocal1, 512);

Result example:

Input (srcLocal0): [1 2 3 ... 512]
Input (srcLocal1): [2 2 2 ... 2]
Output (dstLocal): [4 8 12 ... 2048]

Parent topic: Logical Computation