arm_power_q31.c
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| text/x-c
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CLexer
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r41 | /* ---------------------------------------------------------------------- | ||
* Copyright (C) 2010 ARM Limited. All rights reserved. | ||||
* | ||||
* $Date: 15. July 2011 | ||||
* $Revision: V1.0.10 | ||||
* | ||||
* Project: CMSIS DSP Library | ||||
* Title: arm_power_q31.c | ||||
* | ||||
* Description: Sum of the squares of the elements of a Q31 vector. | ||||
* | ||||
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 | ||||
* | ||||
* Version 1.0.10 2011/7/15 | ||||
* Big Endian support added and Merged M0 and M3/M4 Source code. | ||||
* | ||||
* Version 1.0.3 2010/11/29 | ||||
* Re-organized the CMSIS folders and updated documentation. | ||||
* | ||||
* Version 1.0.2 2010/11/11 | ||||
* Documentation updated. | ||||
* | ||||
* Version 1.0.1 2010/10/05 | ||||
* Production release and review comments incorporated. | ||||
* | ||||
* Version 1.0.0 2010/09/20 | ||||
* Production release and review comments incorporated. | ||||
* -------------------------------------------------------------------- */ | ||||
#include "arm_math.h" | ||||
/** | ||||
* @ingroup groupStats | ||||
*/ | ||||
/** | ||||
* @addtogroup power | ||||
* @{ | ||||
*/ | ||||
/** | ||||
* @brief Sum of the squares of the elements of a Q31 vector. | ||||
* @param[in] *pSrc points to the input vector | ||||
* @param[in] blockSize length of the input vector | ||||
* @param[out] *pResult sum of the squares value returned here | ||||
* @return none. | ||||
* | ||||
* @details | ||||
* <b>Scaling and Overflow Behavior:</b> | ||||
* | ||||
* \par | ||||
* The function is implemented using a 64-bit internal accumulator. | ||||
* The input is represented in 1.31 format. | ||||
* Intermediate multiplication yields a 2.62 format, and this | ||||
* result is 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. | ||||
* With 15 guard bits in the accumulator, there is no risk of overflow, and the | ||||
* full precision of the intermediate multiplication is preserved. | ||||
* Finally, the return result is in 16.48 format. | ||||
* | ||||
*/ | ||||
void arm_power_q31( | ||||
q31_t * pSrc, | ||||
uint32_t blockSize, | ||||
q63_t * pResult) | ||||
{ | ||||
q63_t sum = 0; /* Temporary result storage */ | ||||
q31_t in; | ||||
uint32_t blkCnt; /* loop counter */ | ||||
#ifndef ARM_MATH_CM0 | ||||
/* Run the below code for Cortex-M4 and Cortex-M3 */ | ||||
/*loop Unrolling */ | ||||
blkCnt = blockSize >> 2u; | ||||
/* First part of the processing with loop unrolling. Compute 4 outputs at a time. | ||||
** a second loop below computes the remaining 1 to 3 samples. */ | ||||
while(blkCnt > 0u) | ||||
{ | ||||
/* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */ | ||||
/* Compute Power then shift intermediate results by 14 bits to maintain 16.48 format and then store the result in a temporary variable sum, providing 15 guard bits. */ | ||||
in = *pSrc++; | ||||
sum += ((q63_t) in * in) >> 14u; | ||||
in = *pSrc++; | ||||
sum += ((q63_t) in * in) >> 14u; | ||||
in = *pSrc++; | ||||
sum += ((q63_t) in * in) >> 14u; | ||||
in = *pSrc++; | ||||
sum += ((q63_t) in * in) >> 14u; | ||||
/* Decrement the loop counter */ | ||||
blkCnt--; | ||||
} | ||||
/* If the blockSize is not a multiple of 4, compute any remaining output samples here. | ||||
** No loop unrolling is used. */ | ||||
blkCnt = blockSize % 0x4u; | ||||
#else | ||||
/* Run the below code for Cortex-M0 */ | ||||
/* Loop over blockSize number of values */ | ||||
blkCnt = blockSize; | ||||
#endif /* #ifndef ARM_MATH_CM0 */ | ||||
while(blkCnt > 0u) | ||||
{ | ||||
/* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */ | ||||
/* Compute Power and then store the result in a temporary variable, sum. */ | ||||
in = *pSrc++; | ||||
sum += ((q63_t) in * in) >> 14u; | ||||
/* Decrement the loop counter */ | ||||
blkCnt--; | ||||
} | ||||
/* Store the results in 16.48 format */ | ||||
*pResult = sum; | ||||
} | ||||
/** | ||||
* @} end of power group | ||||
*/ | ||||