WriteSpmBuffer

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	x
Atlas inference product AI Core	√
Atlas inference product Vector Core	x
Atlas training product	√

Function Usage

Copies the data to be overflowed and temporarily stored to the SPM buffer.

Prototype

Applicable to continuous and discontinuous temporary data storage:

template <typename T>
__aicore__ inline void WriteSpmBuffer(const LocalTensor<T>& writeBuffer, const DataCopyParams& copyParams, int32_t writeOffset = 0)

Applicable to continuous temporary data storage:

template <typename T>
__aicore__ inline void WriteSpmBuffer(const LocalTensor<T>& writeBuffer, const int32_t writeSize, int32_t writeOffset = 0)

Parameters

**Table 1** API parameters
Parameter	Input/Output	Meaning
writeBuffer	Input	Local memory to be overflowed and temporarily stored.
copyParams	Input	Movement parameter, DataCopyParams type. For details about the structure definition of DataCopyParams, see Table 2.
writeSize	Input	Number of copied elements.
writeOffset	Input	Offset copied to the SPM buffer, in bytes.

**Table 2** Parameters in the **DataCopyParams** structure
Parameter	Description
blockCount	Number of data chunks to be transferred, which is of the uint16_t type. The value range is [1, 4095].
blockLen	Length of each data chunk to be transferred, in the unit of a data block (32 bytes). The value is of the uint16_t type. The value range is [1, 65535]. Notes: When dst is located in C2PIPE2GM, the unit is 128 bytes. Generally, dst in C2 indicates the length of a data chunk in the source operand. The unit is 64 bytes. For the Atlas 350 Accelerator Card, dst in C2 indicates the length of a data chunk in the source operand. The unit is 32 bytes.
srcGap	Gap between adjacent data chunks of the source operand (the distance from the tail of one data chunk to the head of the next). The unit is a data block (32 bytes). The value is of the uint16_t type and must not exceed the value range of this data type. In the scenario of L1 Buffer -> Fixpipe Buffer, srcGap refers to the gap between adjacent data chunks of the source operand (the distance from the head of one data chunk to the head of the next). The unit is a data block (32 bytes). The value is of the uint16_t type and must not exceed the value range of this data type.
dstGap	Gap between adjacent data chunks of the destination operand (the distance from the tail of one data chunk to the head of the next). The unit is a data block (32 bytes). The value is of the uint16_t type and must not exceed the value range of this data type. Notes: When dst is located in C2PIPE2GM, the unit is 128 bytes. Generally, dst in C2 indicates the length of a data chunk in the source operand. The unit is 64 bytes. For the Atlas 350 Accelerator Card, dst in C2 indicates the length of a data chunk in the source operand. The unit is 32 bytes. In the scenario of L1 Buffer -> Fixpipe Buffer, dstGap refers to the gap between adjacent data chunks of the source operand (the distance from the head of one data chunk to the head of the next). The unit is a data block (32 bytes). The value is of the uint16_t type and must not exceed the value range of this data type.

Constraints

Ensure that writeSize and writeOffset are 32-byte aligned when the data is temporarily stored and copied to L1.
The size of the copied memory cannot exceed the size of the initialized SPM buffer. Otherwise, problems such as overflow violation may occur.

Returns

None

Example

Using DataCopyParams for transfer

AscendC::TPipe pipe;
int dataSize = 32; // Assume that T is of the half type. Allocate the buffer of 32 × sizeof(half) bytes from Unified Buffer.
int offset = 32; // The offset is 32 bytes when data is copied to spmBuffer.
AscendC::DataCopyParams copyParams{1, 2, 0, 0}; // Transfer a data chunk from Unified Buffer. The length of the data chunk is two data blocks, and the length of a data block is 32 bytes.
// writeLocal is a LocalTensor of the half type in the SPM buffer.
pipe.WriteSpmBuffer(writeLocal, copyParams, offset); // Transfer the data chunk from Unified Buffer to the SPM buffer.
pipe.ReadSpmBuffer(writeLocal, copyParams, offset); // Read the data temporarily stored in the SPM buffer back to the local data.
...
// When Unified Buffer has sufficient memory, transfer the data chunk temporarily stored in the SPM buffer back to the global memory. dstGlobal is a GlobalTensor of the half type.
AscendC::DataCopy(dstGlobal, writeLocal, copyParams);

Using writeSize for consecutive transfer

AscendC::TPipe pipe;
int dataSize = 32; // Assume that T is of the half type. Allocate the buffer of 32 × sizeof(half) bytes from Unified Buffer.
int offset = 32; // The offset is 32 bytes when data is copied to spmBuffer.
;
// writeLocal is a LocalTensor of the half type in the SPM buffer.
pipe.WriteSpmBuffer(writeLocal, dataSize, offset); // Transfer the data chunk from Unified Buffer to the SPM buffer.
pipe.ReadSpmBuffer(writeLocal, dataSize, offset); // Read the data temporarily stored in the SPM buffer back to the local data.
...
// When Unified Buffer has sufficient memory, transfer the data chunk temporarily stored in the SPM buffer back to the global memory. dstGlobal is a GlobalTensor of the half type.
AscendC::DataCopy(dstGlobal, writeLocal, dataSize);

Parent topic: TPipe