CMSIS-DSP: Complex Dot Product

| CMSIS-DSP Version 1.8.0 CMSIS DSP Software Library

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Complex Dot Product
Complex Math Functions

## Functions

void | arm_cmplx_dot_prod_f32 (const float32_t *pSrcA, const float32_t *pSrcB, uint32_t numSamples, float32_t *realResult, float32_t *imagResult)
| Floating-point complex dot product. More...
void | arm_cmplx_dot_prod_q15 (const q15_t *pSrcA, const q15_t *pSrcB, uint32_t numSamples, q31_t *realResult, q31_t *imagResult)
| Q15 complex dot product. More...
void | arm_cmplx_dot_prod_q31 (const q31_t *pSrcA, const q31_t *pSrcB, uint32_t numSamples, q63_t *realResult, q63_t *imagResult)
| Q31 complex dot product. More...

## Description

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

The `pSrcA` points to the first complex input vector and `pSrcB` points to the second complex input vector. `numSamples` specifies the number of complex samples and the data in each array is stored in an interleaved fashion (real, imag, real, imag, ...). Each array has a total of `2*numSamples` values.

The underlying algorithm is used:

    realResult = 0;
    imagResult = 0;
    for (n = 0; n < numSamples; n++) {
        realResult += pSrcA[(2*n)+0] * pSrcB[(2*n)+0] - pSrcA[(2*n)+1] * pSrcB[(2*n)+1];
        imagResult += pSrcA[(2*n)+0] * pSrcB[(2*n)+1] + pSrcA[(2*n)+1] * pSrcB[(2*n)+0];
    }

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

## Function Documentation

void arm_cmplx_dot_prod_f32 | ( | const float32_t * | pSrcA,
|  | const float32_t * | pSrcB,
|  | uint32_t | numSamples,
|  | float32_t * | realResult,
|  | float32_t * | imagResult
| ) |  |

Parameters

  [in] | pSrcA | points to the first input vector
  [in] | pSrcB | points to the second input vector
  [in] | numSamples | number of samples in each vector
  [out] | realResult | real part of the result returned here
  [out] | imagResult | imaginary part of the result returned here

Returns
  none

void arm_cmplx_dot_prod_q15 | ( | const q15_t * | pSrcA,
|  | const q15_t * | pSrcB,
|  | uint32_t | numSamples,
|  | q31_t * | realResult,
|  | q31_t * | imagResult
| ) |  |

Parameters

  [in] | pSrcA | points to the first input vector
  [in] | pSrcB | points to the second input vector
  [in] | numSamples | number of samples in each vector
  [out] | realResult | real part of the result returned here
  [out] | imagResult | imaginary part of the result returned her

Returns
  none

Scaling and Overflow Behavior
  The function is implemented using an internal 64-bit accumulator. The intermediate 1.15 by 1.15 multiplications are performed with full precision and yield a 2.30 result. These are accumulated in a 64-bit accumulator with 34.30 precision. As a final step, the accumulators are converted to 8.24 format. The return results `realResult` and `imagResult` are in 8.24 format.

void arm_cmplx_dot_prod_q31 | ( | const q31_t * | pSrcA,
|  | const q31_t * | pSrcB,
|  | uint32_t | numSamples,
|  | q63_t * | realResult,
|  | q63_t * | imagResult
| ) |  |

Parameters

  [in] | pSrcA | points to the first input vector
  [in] | pSrcB | points to the second input vector
  [in] | numSamples | number of samples in each vector
  [out] | realResult | real part of the result returned here
  [out] | imagResult | imaginary part of the result returned here

Returns
  none

Scaling and Overflow Behavior
  The function is implemented using an internal 64-bit accumulator. The intermediate 1.31 by 1.31 multiplications are performed with 64-bit precision and then shifted to 16.48 format. The internal real and imaginary accumulators are in 16.48 format and provide 15 guard bits. Additions are nonsaturating and no overflow will occur as long as `numSamples` is less than 32768. The return results `realResult` and `imagResult` are in 16.48 format. Input down scaling is not required.