FFT_2D

Applicable Products

Function Description

API function

• asdFftMakePlan2D: Initializes the 2D FFT configuration.

• asdFftExecC2C: performs FFT from a complex number to another complex number.
• asdFftExecC2R: performs FFT from a complex number to a real number.

• asdFftExecR2C: performs FFT from a real number to a complex number.

Formula

Fourier transform indicates a linear integral transform. It is used to transform signals between the time domain and the frequency domain. It is widely used in physics and engineering. For a signal with a given length of N, the DFT formula is as follows:

The coefficient matrix (N*N) and time-domain signal (N*1) are considered as two tensors. DFT can be completed by directly using matrix multiplication on the NPU. However, the time complexity is too high. Therefore, FFT is required. The basic principle is to split a sequence into sub-sequences by using the rotation symmetry of trigonometric functions in the complex domain. The butterfly operation is performed to reduce calculation complexity.

Function Prototype

• AspbStatus asdFftMakePlan2D(asdFftHandle handle, int64_t fftSizeX, int64_t fftSizeY, asdFftType fftType, asdFftDirection direction, int32_t batchSize)
• AspbStatus asdFftExecC2C(asdFftHandle handle, const aclTensor *input, const aclTensor *output)
• AspbStatus asdFftExecC2R(asdFftHandle handle, const aclTensor *input, const aclTensor *output)
• AspbStatus asdFftExecR2C(asdFftHandle handle, const aclTensor *input, const aclTensor *output)

Parameter Description

• asdFftMakePlan2D

  Parameter	Input/Output	Type	Description
  handle	Input	asdFftHandle	Handle of the FFT operator. You need to manually create the asdFftHandle object.
  fftSizeX	Input	int64_t	M in the formula, which indicates the FFT signal length (the first dimension).
  fftSizeY	Input	int64_t	N in the formula, which indicates the FFT signal length (the second dimension).
  fftType	Input	asdFftType	FFT type. The options are as follows: - ASCEND_FFT_C2C - ASCEND_FFT_C2R - ASCEND_FFT_R2C
  direction	Input	asdFftDirection	Forward transform or inverse transform: - ASCEND_FFT_FORWARD - ASCEND_FFT_INVERSE
  batchSize	Input	int32_t	Number of data batches in the FFT batch processing operation.

• asdFftExecC2C

  Parameter	Input/Output	Type	Description
  handle	Input	asdFftHandle	Handle of the FFT operator. You need to manually create the asdFftHandle object.
  inData	Input	const aclTensor *	x in the formula, which is a tensor on the device. The data type can only be COMPELX64, the data format can be ND, and the input shape is (batchSize, fftSizeX, fftSizeY).
  outData	Output	aclTensor *	y in the formula, which is a tensor on the device. The data type can only be COMPELX64, the data format can be ND, and the input shape is (batchSize, fftSizeX, fftSizeY).

• asdFftExecC2R

  Parameter	Input/Output	Type	Description
  handle	Input	asdFftHandle	Handle of the FFT operator. You need to manually create the asdFftHandle object.
  inData	Input	const aclTensor *	x in the formula, which is a tensor on the device. The data type can only be COMPELX64, the data format can be ND, and the input shape is (batchSize, fftSizeX, fftSizeY/2+1).
  outData	Output	aclTensor *	y in the formula, which is a tensor on the device. The data type can only be FLOAT32, the data format can be ND, and the input shape is (batchSize, fftSizeX, fftSizeY).

• asdFftExecR2C

  Parameter	Input/Output	Type	Description
  handle	Input	asdFftHandle	Handle of the FFT operator. You need to manually create the asdFftHandle object.
  inData	Input	const aclTensor *	x in the formula, which is a tensor on the device. The data type can only be FLOAT32, the data format can be ND, and the input shape is (batchSize, fftSizeX, fftSizeY).
  outData	Output	aclTensor *	y in the formula, which is a tensor on the device. The data type can only be COMPELX64, the data format can be ND, and the input shape is (batchSize, fftSizeX, fftSizeY/2+1).

Return Value Description

For details about the return values, see Return Value.

Constraints

Local update is not supported in FFT_2D. That is, the input tensor and output tensor cannot be the same tensor.

• asdFftMakePlan2D
  • The values of fftSizeX and fftSizeY must be less than or equal to 2^27, and the prime factors after factorization must not be greater than 199.
  • There is no additional restriction on batchSize within the storage scope.
  • The theoretical range of the number of input elements is [1, 2^30].
  • The input elements cannot be inf, -inf, or nan. If the input contains these values, the result is undefined.
• asdFftExecC2C

  None

• asdFftExecC2R

  None

• asdFftExecR2C

  None

Calling Example

For details about the operator calling example, see FFT_2D.