Vector Dot Product

Functions
void	arm_dot_prod_f32 (const float32_t *pSrcA, const float32_t *pSrcB, uint32_t blockSize, float32_t *result)
	Dot product of floating-point vectors. More...
void	arm_dot_prod_q15 (const q15_t *pSrcA, const q15_t *pSrcB, uint32_t blockSize, q63_t *result)
	Dot product of Q15 vectors. More...
void	arm_dot_prod_q31 (const q31_t *pSrcA, const q31_t *pSrcB, uint32_t blockSize, q63_t *result)
	Dot product of Q31 vectors. More...
void	arm_dot_prod_q7 (const q7_t *pSrcA, const q7_t *pSrcB, uint32_t blockSize, q31_t *result)
	Dot product of Q7 vectors. More...

Description

Computes the dot product of two vectors. The vectors are multiplied element-by-element and then summed.

    sum = pSrcA[0]*pSrcB[0] + pSrcA[1]*pSrcB[1] + ... + pSrcA[blockSize-1]*pSrcB[blockSize-1]

There are separate functions for floating-point, Q7, Q15, and Q31 data types.

Function Documentation

void arm_dot_prod_f32	(	const float32_t *	pSrcA,
		const float32_t *	pSrcB,
		uint32_t	blockSize,
		float32_t *	result
	)

Parameters

[in]	pSrcA	points to the first input vector.
[in]	pSrcB	points to the second input vector.
[in]	blockSize	number of samples in each vector.
[out]	result	output result returned here.

Returns

none

void arm_dot_prod_q15	(	const q15_t *	pSrcA,
		const q15_t *	pSrcB,
		uint32_t	blockSize,
		q63_t *	result
	)

Parameters

[in]	pSrcA	points to the first input vector
[in]	pSrcB	points to the second input vector
[in]	blockSize	number of samples in each vector
[out]	result	output result returned here

Returns

none

Scaling and Overflow Behavior

The intermediate multiplications are in 1.15 x 1.15 = 2.30 format and these results are added to a 64-bit accumulator in 34.30 format. Nonsaturating additions are used and given that there are 33 guard bits in the accumulator there is no risk of overflow. The return result is in 34.30 format.

void arm_dot_prod_q31	(	const q31_t *	pSrcA,
		const q31_t *	pSrcB,
		uint32_t	blockSize,
		q63_t *	result
	)

Parameters

[in]	pSrcA	points to the first input vector.
[in]	pSrcB	points to the second input vector.
[in]	blockSize	number of samples in each vector.
[out]	result	output result returned here.

Returns

none

Scaling and Overflow Behavior

The intermediate multiplications are in 1.31 x 1.31 = 2.62 format and these are truncated to 2.48 format by discarding the lower 14 bits. The 2.48 result is then added without saturation to a 64-bit accumulator in 16.48 format. There are 15 guard bits in the accumulator and there is no risk of overflow as long as the length of the vectors is less than 2^16 elements. The return result is in 16.48 format.

void arm_dot_prod_q7	(	const q7_t *	pSrcA,
		const q7_t *	pSrcB,
		uint32_t	blockSize,
		q31_t *	result
	)

Parameters

[in]	pSrcA	points to the first input vector
[in]	pSrcB	points to the second input vector
[in]	blockSize	number of samples in each vector
[out]	result	output result returned here

Returns

none

Scaling and Overflow Behavior

The intermediate multiplications are in 1.7 x 1.7 = 2.14 format and these results are added to an accumulator in 18.14 format. Nonsaturating additions are used and there is no danger of wrap around as long as the vectors are less than 2^18 elements long. The return result is in 18.14 format.