pigweed / third_party / github / STMicroelectronics / cmsis_core / be0e91fb4ba19a2ee427ba8b6b75b43eb02b2810 / . / DSP / Source / BasicMathFunctions / arm_dot_prod_q31.c

/* ---------------------------------------------------------------------- | |

* Project: CMSIS DSP Library | |

* Title: arm_dot_prod_q31.c | |

* Description: Q31 dot product | |

* | |

* $Date: 18. March 2019 | |

* $Revision: V1.6.0 | |

* | |

* Target Processor: Cortex-M cores | |

* -------------------------------------------------------------------- */ | |

/* | |

* Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved. | |

* | |

* SPDX-License-Identifier: Apache-2.0 | |

* | |

* Licensed under the Apache License, Version 2.0 (the License); you may | |

* not use this file except in compliance with the License. | |

* You may obtain a copy of the License at | |

* | |

* www.apache.org/licenses/LICENSE-2.0 | |

* | |

* Unless required by applicable law or agreed to in writing, software | |

* distributed under the License is distributed on an AS IS BASIS, WITHOUT | |

* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |

* See the License for the specific language governing permissions and | |

* limitations under the License. | |

*/ | |

#include "arm_math.h" | |

/** | |

@ingroup groupMath | |

*/ | |

/** | |

@addtogroup BasicDotProd | |

@{ | |

*/ | |

/** | |

@brief Dot product of Q31 vectors. | |

@param[in] pSrcA points to the first input vector. | |

@param[in] pSrcB points to the second input vector. | |

@param[in] blockSize number of samples in each vector. | |

@param[out] result output result returned here. | |

@return none | |

@par 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_q31( | |

const q31_t * pSrcA, | |

const q31_t * pSrcB, | |

uint32_t blockSize, | |

q63_t * result) | |

{ | |

uint32_t blkCnt; /* Loop counter */ | |

q63_t sum = 0; /* Temporary return variable */ | |

#if defined (ARM_MATH_LOOPUNROLL) | |

/* Loop unrolling: Compute 4 outputs at a time */ | |

blkCnt = blockSize >> 2U; | |

while (blkCnt > 0U) | |

{ | |

/* C = A[0]* B[0] + A[1]* B[1] + A[2]* B[2] + .....+ A[blockSize-1]* B[blockSize-1] */ | |

/* Calculate dot product and store result in a temporary buffer. */ | |

sum += ((q63_t) *pSrcA++ * *pSrcB++) >> 14U; | |

sum += ((q63_t) *pSrcA++ * *pSrcB++) >> 14U; | |

sum += ((q63_t) *pSrcA++ * *pSrcB++) >> 14U; | |

sum += ((q63_t) *pSrcA++ * *pSrcB++) >> 14U; | |

/* Decrement loop counter */ | |

blkCnt--; | |

} | |

/* Loop unrolling: Compute remaining outputs */ | |

blkCnt = blockSize % 0x4U; | |

#else | |

/* Initialize blkCnt with number of samples */ | |

blkCnt = blockSize; | |

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */ | |

while (blkCnt > 0U) | |

{ | |

/* C = A[0]* B[0] + A[1]* B[1] + A[2]* B[2] + .....+ A[blockSize-1]* B[blockSize-1] */ | |

/* Calculate dot product and store result in a temporary buffer. */ | |

sum += ((q63_t) *pSrcA++ * *pSrcB++) >> 14U; | |

/* Decrement loop counter */ | |

blkCnt--; | |

} | |

/* Store result in destination buffer in 16.48 format */ | |

*result = sum; | |

} | |

/** | |

@} end of BasicDotProd group | |

*/ |