arm_correlate_q15.c
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CLexer
r71 | /* ---------------------------------------------------------------------- | |||
* Copyright (C) 2010 ARM Limited. All rights reserved. | ||||
* | ||||
* $Date: 15. July 2011 | ||||
* $Revision: V1.0.10 | ||||
* | ||||
* Project: CMSIS DSP Library | ||||
* Title: arm_correlate_q15.c | ||||
* | ||||
* Description: Correlation of Q15 sequences. | ||||
* | ||||
* 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 | ||||
* | ||||
* Version 0.0.7 2010/06/10 | ||||
* Misra-C changes done | ||||
* | ||||
* -------------------------------------------------------------------- */ | ||||
#include "arm_math.h" | ||||
/** | ||||
* @ingroup groupFilters | ||||
*/ | ||||
/** | ||||
* @addtogroup Corr | ||||
* @{ | ||||
*/ | ||||
/** | ||||
* @brief Correlation of Q15 sequences. | ||||
* @param[in] *pSrcA points to the first input sequence. | ||||
* @param[in] srcALen length of the first input sequence. | ||||
* @param[in] *pSrcB points to the second input sequence. | ||||
* @param[in] srcBLen length of the second input sequence. | ||||
* @param[out] *pDst points to the location where the output result is written. Length 2 * max(srcALen, srcBLen) - 1. | ||||
* @return none. | ||||
* | ||||
* @details | ||||
* <b>Scaling and Overflow Behavior:</b> | ||||
* | ||||
* \par | ||||
* The function is implemented using a 64-bit internal accumulator. | ||||
* Both inputs are in 1.15 format and multiplications yield a 2.30 result. | ||||
* The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format. | ||||
* This approach provides 33 guard bits and there is no risk of overflow. | ||||
* The 34.30 result is then truncated to 34.15 format by discarding the low 15 bits and then saturated to 1.15 format. | ||||
* | ||||
* \par | ||||
* Refer to <code>arm_correlate_fast_q15()</code> for a faster but less precise version of this function for Cortex-M3 and Cortex-M4. | ||||
*/ | ||||
void arm_correlate_q15( | ||||
q15_t * pSrcA, | ||||
uint32_t srcALen, | ||||
q15_t * pSrcB, | ||||
uint32_t srcBLen, | ||||
q15_t * pDst) | ||||
{ | ||||
#ifndef ARM_MATH_CM0 | ||||
/* Run the below code for Cortex-M4 and Cortex-M3 */ | ||||
q15_t *pIn1; /* inputA pointer */ | ||||
q15_t *pIn2; /* inputB pointer */ | ||||
q15_t *pOut = pDst; /* output pointer */ | ||||
q63_t sum, acc0, acc1, acc2, acc3; /* Accumulators */ | ||||
q15_t *px; /* Intermediate inputA pointer */ | ||||
q15_t *py; /* Intermediate inputB pointer */ | ||||
q15_t *pSrc1; /* Intermediate pointers */ | ||||
q31_t x0, x1, x2, x3, c0; /* temporary variables for holding input and coefficient values */ | ||||
uint32_t j, k = 0u, count, blkCnt, outBlockSize, blockSize1, blockSize2, blockSize3; /* loop counter */ | ||||
int32_t inc = 1; /* Destination address modifier */ | ||||
q31_t *pb; /* 32 bit pointer for inputB buffer */ | ||||
/* The algorithm implementation is based on the lengths of the inputs. */ | ||||
/* srcB is always made to slide across srcA. */ | ||||
/* So srcBLen is always considered as shorter or equal to srcALen */ | ||||
/* But CORR(x, y) is reverse of CORR(y, x) */ | ||||
/* So, when srcBLen > srcALen, output pointer is made to point to the end of the output buffer */ | ||||
/* and the destination pointer modifier, inc is set to -1 */ | ||||
/* If srcALen > srcBLen, zero pad has to be done to srcB to make the two inputs of same length */ | ||||
/* But to improve the performance, | ||||
* we include zeroes in the output instead of zero padding either of the the inputs*/ | ||||
/* If srcALen > srcBLen, | ||||
* (srcALen - srcBLen) zeroes has to included in the starting of the output buffer */ | ||||
/* If srcALen < srcBLen, | ||||
* (srcALen - srcBLen) zeroes has to included in the ending of the output buffer */ | ||||
if(srcALen >= srcBLen) | ||||
{ | ||||
/* Initialization of inputA pointer */ | ||||
pIn1 = (pSrcA); | ||||
/* Initialization of inputB pointer */ | ||||
pIn2 = (pSrcB); | ||||
/* Number of output samples is calculated */ | ||||
outBlockSize = (2u * srcALen) - 1u; | ||||
/* When srcALen > srcBLen, zero padding is done to srcB | ||||
* to make their lengths equal. | ||||
* Instead, (outBlockSize - (srcALen + srcBLen - 1)) | ||||
* number of output samples are made zero */ | ||||
j = outBlockSize - (srcALen + (srcBLen - 1u)); | ||||
/* Updating the pointer position to non zero value */ | ||||
pOut += j; | ||||
} | ||||
else | ||||
{ | ||||
/* Initialization of inputA pointer */ | ||||
pIn1 = (pSrcB); | ||||
/* Initialization of inputB pointer */ | ||||
pIn2 = (pSrcA); | ||||
/* srcBLen is always considered as shorter or equal to srcALen */ | ||||
j = srcBLen; | ||||
srcBLen = srcALen; | ||||
srcALen = j; | ||||
/* CORR(x, y) = Reverse order(CORR(y, x)) */ | ||||
/* Hence set the destination pointer to point to the last output sample */ | ||||
pOut = pDst + ((srcALen + srcBLen) - 2u); | ||||
/* Destination address modifier is set to -1 */ | ||||
inc = -1; | ||||
} | ||||
/* The function is internally | ||||
* divided into three parts according to the number of multiplications that has to be | ||||
* taken place between inputA samples and inputB samples. In the first part of the | ||||
* algorithm, the multiplications increase by one for every iteration. | ||||
* In the second part of the algorithm, srcBLen number of multiplications are done. | ||||
* In the third part of the algorithm, the multiplications decrease by one | ||||
* for every iteration.*/ | ||||
/* The algorithm is implemented in three stages. | ||||
* The loop counters of each stage is initiated here. */ | ||||
blockSize1 = srcBLen - 1u; | ||||
blockSize2 = srcALen - (srcBLen - 1u); | ||||
blockSize3 = blockSize1; | ||||
/* -------------------------- | ||||
* Initializations of stage1 | ||||
* -------------------------*/ | ||||
/* sum = x[0] * y[srcBlen - 1] | ||||
* sum = x[0] * y[srcBlen - 2] + x[1] * y[srcBlen - 1] | ||||
* .... | ||||
* sum = x[0] * y[0] + x[1] * y[1] +...+ x[srcBLen - 1] * y[srcBLen - 1] | ||||
*/ | ||||
/* In this stage the MAC operations are increased by 1 for every iteration. | ||||
The count variable holds the number of MAC operations performed */ | ||||
count = 1u; | ||||
/* Working pointer of inputA */ | ||||
px = pIn1; | ||||
/* Working pointer of inputB */ | ||||
pSrc1 = pIn2 + (srcBLen - 1u); | ||||
py = pSrc1; | ||||
/* ------------------------ | ||||
* Stage1 process | ||||
* ----------------------*/ | ||||
/* The first loop starts here */ | ||||
while(blockSize1 > 0u) | ||||
{ | ||||
/* Accumulator is made zero for every iteration */ | ||||
sum = 0; | ||||
/* Apply loop unrolling and compute 4 MACs simultaneously. */ | ||||
k = count >> 2; | ||||
/* First part of the processing with loop unrolling. Compute 4 MACs at a time. | ||||
** a second loop below computes MACs for the remaining 1 to 3 samples. */ | ||||
while(k > 0u) | ||||
{ | ||||
/* x[0] * y[srcBLen - 4] , x[1] * y[srcBLen - 3] */ | ||||
sum = __SMLALD(*__SIMD32(px)++, *__SIMD32(py)++, sum); | ||||
/* x[3] * y[srcBLen - 1] , x[2] * y[srcBLen - 2] */ | ||||
sum = __SMLALD(*__SIMD32(px)++, *__SIMD32(py)++, sum); | ||||
/* Decrement the loop counter */ | ||||
k--; | ||||
} | ||||
/* If the count is not a multiple of 4, compute any remaining MACs here. | ||||
** No loop unrolling is used. */ | ||||
k = count % 0x4u; | ||||
while(k > 0u) | ||||
{ | ||||
/* Perform the multiply-accumulates */ | ||||
/* x[0] * y[srcBLen - 1] */ | ||||
sum = __SMLALD(*px++, *py++, sum); | ||||
/* Decrement the loop counter */ | ||||
k--; | ||||
} | ||||
/* Store the result in the accumulator in the destination buffer. */ | ||||
*pOut = (q15_t) (__SSAT((sum >> 15), 16)); | ||||
/* Destination pointer is updated according to the address modifier, inc */ | ||||
pOut += inc; | ||||
/* Update the inputA and inputB pointers for next MAC calculation */ | ||||
py = pSrc1 - count; | ||||
px = pIn1; | ||||
/* Increment the MAC count */ | ||||
count++; | ||||
/* Decrement the loop counter */ | ||||
blockSize1--; | ||||
} | ||||
/* -------------------------- | ||||
* Initializations of stage2 | ||||
* ------------------------*/ | ||||
/* sum = x[0] * y[0] + x[1] * y[1] +...+ x[srcBLen-1] * y[srcBLen-1] | ||||
* sum = x[1] * y[0] + x[2] * y[1] +...+ x[srcBLen] * y[srcBLen-1] | ||||
* .... | ||||
* sum = x[srcALen-srcBLen-2] * y[0] + x[srcALen-srcBLen-1] * y[1] +...+ x[srcALen-1] * y[srcBLen-1] | ||||
*/ | ||||
/* Working pointer of inputA */ | ||||
px = pIn1; | ||||
/* Working pointer of inputB */ | ||||
py = pIn2; | ||||
/* Initialize inputB pointer of type q31 */ | ||||
pb = (q31_t *) (py); | ||||
/* count is index by which the pointer pIn1 to be incremented */ | ||||
count = 0u; | ||||
/* ------------------- | ||||
* Stage2 process | ||||
* ------------------*/ | ||||
/* Stage2 depends on srcBLen as in this stage srcBLen number of MACS are performed. | ||||
* So, to loop unroll over blockSize2, | ||||
* srcBLen should be greater than or equal to 4, to loop unroll the srcBLen loop */ | ||||
if(srcBLen >= 4u) | ||||
{ | ||||
/* Loop unroll over blockSize2, by 4 */ | ||||
blkCnt = blockSize2 >> 2u; | ||||
while(blkCnt > 0u) | ||||
{ | ||||
/* Set all accumulators to zero */ | ||||
acc0 = 0; | ||||
acc1 = 0; | ||||
acc2 = 0; | ||||
acc3 = 0; | ||||
/* read x[0], x[1] samples */ | ||||
x0 = *(q31_t *) (px++); | ||||
/* read x[1], x[2] samples */ | ||||
x1 = *(q31_t *) (px++); | ||||
/* Apply loop unrolling and compute 4 MACs simultaneously. */ | ||||
k = srcBLen >> 2u; | ||||
/* First part of the processing with loop unrolling. Compute 4 MACs at a time. | ||||
** a second loop below computes MACs for the remaining 1 to 3 samples. */ | ||||
do | ||||
{ | ||||
/* Read the first two inputB samples using SIMD: | ||||
* y[0] and y[1] */ | ||||
c0 = *(pb++); | ||||
/* acc0 += x[0] * y[0] + x[1] * y[1] */ | ||||
acc0 = __SMLALD(x0, c0, acc0); | ||||
/* acc1 += x[1] * y[0] + x[2] * y[1] */ | ||||
acc1 = __SMLALD(x1, c0, acc1); | ||||
/* Read x[2], x[3] */ | ||||
x2 = *(q31_t *) (px++); | ||||
/* Read x[3], x[4] */ | ||||
x3 = *(q31_t *) (px++); | ||||
/* acc2 += x[2] * y[0] + x[3] * y[1] */ | ||||
acc2 = __SMLALD(x2, c0, acc2); | ||||
/* acc3 += x[3] * y[0] + x[4] * y[1] */ | ||||
acc3 = __SMLALD(x3, c0, acc3); | ||||
/* Read y[2] and y[3] */ | ||||
c0 = *(pb++); | ||||
/* acc0 += x[2] * y[2] + x[3] * y[3] */ | ||||
acc0 = __SMLALD(x2, c0, acc0); | ||||
/* acc1 += x[3] * y[2] + x[4] * y[3] */ | ||||
acc1 = __SMLALD(x3, c0, acc1); | ||||
/* Read x[4], x[5] */ | ||||
x0 = *(q31_t *) (px++); | ||||
/* Read x[5], x[6] */ | ||||
x1 = *(q31_t *) (px++); | ||||
/* acc2 += x[4] * y[2] + x[5] * y[3] */ | ||||
acc2 = __SMLALD(x0, c0, acc2); | ||||
/* acc3 += x[5] * y[2] + x[6] * y[3] */ | ||||
acc3 = __SMLALD(x1, c0, acc3); | ||||
} while(--k); | ||||
/* For the next MAC operations, SIMD is not used | ||||
* So, the 16 bit pointer if inputB, py is updated */ | ||||
py = (q15_t *) (pb); | ||||
/* If the srcBLen is not a multiple of 4, compute any remaining MACs here. | ||||
** No loop unrolling is used. */ | ||||
k = srcBLen % 0x4u; | ||||
if(k == 1u) | ||||
{ | ||||
/* Read y[4] */ | ||||
c0 = *py; | ||||
#ifdef ARM_MATH_BIG_ENDIAN | ||||
c0 = c0 << 16u; | ||||
#else | ||||
c0 = c0 & 0x0000FFFF; | ||||
#endif /* #ifdef ARM_MATH_BIG_ENDIAN */ | ||||
/* Read x[7] */ | ||||
x3 = *(q31_t *) px++; | ||||
/* Perform the multiply-accumulates */ | ||||
acc0 = __SMLALD(x0, c0, acc0); | ||||
acc1 = __SMLALD(x1, c0, acc1); | ||||
acc2 = __SMLALDX(x1, c0, acc2); | ||||
acc3 = __SMLALDX(x3, c0, acc3); | ||||
} | ||||
if(k == 2u) | ||||
{ | ||||
/* Read y[4], y[5] */ | ||||
c0 = *(pb); | ||||
/* Read x[7], x[8] */ | ||||
x3 = *(q31_t *) px++; | ||||
/* Read x[9] */ | ||||
x2 = *(q31_t *) px++; | ||||
/* Perform the multiply-accumulates */ | ||||
acc0 = __SMLALD(x0, c0, acc0); | ||||
acc1 = __SMLALD(x1, c0, acc1); | ||||
acc2 = __SMLALD(x3, c0, acc2); | ||||
acc3 = __SMLALD(x2, c0, acc3); | ||||
} | ||||
if(k == 3u) | ||||
{ | ||||
/* Read y[4], y[5] */ | ||||
c0 = *pb++; | ||||
/* Read x[7], x[8] */ | ||||
x3 = *(q31_t *) px++; | ||||
/* Read x[9] */ | ||||
x2 = *(q31_t *) px++; | ||||
/* Perform the multiply-accumulates */ | ||||
acc0 = __SMLALD(x0, c0, acc0); | ||||
acc1 = __SMLALD(x1, c0, acc1); | ||||
acc2 = __SMLALD(x3, c0, acc2); | ||||
acc3 = __SMLALD(x2, c0, acc3); | ||||
/* Read y[6] */ | ||||
#ifdef ARM_MATH_BIG_ENDIAN | ||||
c0 = (*pb); | ||||
c0 = c0 & 0xFFFF0000; | ||||
#else | ||||
c0 = (q15_t) (*pb); | ||||
c0 = c0 & 0x0000FFFF; | ||||
#endif /* #ifdef ARM_MATH_BIG_ENDIAN */ | ||||
/* Read x[10] */ | ||||
x3 = *(q31_t *) px++; | ||||
/* Perform the multiply-accumulates */ | ||||
acc0 = __SMLALDX(x1, c0, acc0); | ||||
acc1 = __SMLALD(x2, c0, acc1); | ||||
acc2 = __SMLALDX(x2, c0, acc2); | ||||
acc3 = __SMLALDX(x3, c0, acc3); | ||||
} | ||||
/* Store the result in the accumulator in the destination buffer. */ | ||||
*pOut = (q15_t) (__SSAT(acc0 >> 15, 16)); | ||||
/* Destination pointer is updated according to the address modifier, inc */ | ||||
pOut += inc; | ||||
*pOut = (q15_t) (__SSAT(acc1 >> 15, 16)); | ||||
pOut += inc; | ||||
*pOut = (q15_t) (__SSAT(acc2 >> 15, 16)); | ||||
pOut += inc; | ||||
*pOut = (q15_t) (__SSAT(acc3 >> 15, 16)); | ||||
pOut += inc; | ||||
/* Increment the count by 4 as 4 output values are computed */ | ||||
count += 4u; | ||||
/* Update the inputA and inputB pointers for next MAC calculation */ | ||||
px = pIn1 + count; | ||||
py = pIn2; | ||||
pb = (q31_t *) (py); | ||||
/* Decrement the loop counter */ | ||||
blkCnt--; | ||||
} | ||||
/* If the blockSize2 is not a multiple of 4, compute any remaining output samples here. | ||||
** No loop unrolling is used. */ | ||||
blkCnt = blockSize2 % 0x4u; | ||||
while(blkCnt > 0u) | ||||
{ | ||||
/* Accumulator is made zero for every iteration */ | ||||
sum = 0; | ||||
/* Apply loop unrolling and compute 4 MACs simultaneously. */ | ||||
k = srcBLen >> 2u; | ||||
/* First part of the processing with loop unrolling. Compute 4 MACs at a time. | ||||
** a second loop below computes MACs for the remaining 1 to 3 samples. */ | ||||
while(k > 0u) | ||||
{ | ||||
/* Perform the multiply-accumulates */ | ||||
sum += ((q63_t) * px++ * *py++); | ||||
sum += ((q63_t) * px++ * *py++); | ||||
sum += ((q63_t) * px++ * *py++); | ||||
sum += ((q63_t) * px++ * *py++); | ||||
/* Decrement the loop counter */ | ||||
k--; | ||||
} | ||||
/* If the srcBLen is not a multiple of 4, compute any remaining MACs here. | ||||
** No loop unrolling is used. */ | ||||
k = srcBLen % 0x4u; | ||||
while(k > 0u) | ||||
{ | ||||
/* Perform the multiply-accumulates */ | ||||
sum += ((q63_t) * px++ * *py++); | ||||
/* Decrement the loop counter */ | ||||
k--; | ||||
} | ||||
/* Store the result in the accumulator in the destination buffer. */ | ||||
*pOut = (q15_t) (__SSAT(sum >> 15, 16)); | ||||
/* Destination pointer is updated according to the address modifier, inc */ | ||||
pOut += inc; | ||||
/* Increment count by 1, as one output value is computed */ | ||||
count++; | ||||
/* Update the inputA and inputB pointers for next MAC calculation */ | ||||
px = pIn1 + count; | ||||
py = pIn2; | ||||
/* Decrement the loop counter */ | ||||
blkCnt--; | ||||
} | ||||
} | ||||
else | ||||
{ | ||||
/* If the srcBLen is not a multiple of 4, | ||||
* the blockSize2 loop cannot be unrolled by 4 */ | ||||
blkCnt = blockSize2; | ||||
while(blkCnt > 0u) | ||||
{ | ||||
/* Accumulator is made zero for every iteration */ | ||||
sum = 0; | ||||
/* Loop over srcBLen */ | ||||
k = srcBLen; | ||||
while(k > 0u) | ||||
{ | ||||
/* Perform the multiply-accumulate */ | ||||
sum += ((q63_t) * px++ * *py++); | ||||
/* Decrement the loop counter */ | ||||
k--; | ||||
} | ||||
/* Store the result in the accumulator in the destination buffer. */ | ||||
*pOut = (q15_t) (__SSAT(sum >> 15, 16)); | ||||
/* Destination pointer is updated according to the address modifier, inc */ | ||||
pOut += inc; | ||||
/* Increment the MAC count */ | ||||
count++; | ||||
/* Update the inputA and inputB pointers for next MAC calculation */ | ||||
px = pIn1 + count; | ||||
py = pIn2; | ||||
/* Decrement the loop counter */ | ||||
blkCnt--; | ||||
} | ||||
} | ||||
/* -------------------------- | ||||
* Initializations of stage3 | ||||
* -------------------------*/ | ||||
/* sum += x[srcALen-srcBLen+1] * y[0] + x[srcALen-srcBLen+2] * y[1] +...+ x[srcALen-1] * y[srcBLen-1] | ||||
* sum += x[srcALen-srcBLen+2] * y[0] + x[srcALen-srcBLen+3] * y[1] +...+ x[srcALen-1] * y[srcBLen-1] | ||||
* .... | ||||
* sum += x[srcALen-2] * y[0] + x[srcALen-1] * y[1] | ||||
* sum += x[srcALen-1] * y[0] | ||||
*/ | ||||
/* In this stage the MAC operations are decreased by 1 for every iteration. | ||||
The count variable holds the number of MAC operations performed */ | ||||
count = srcBLen - 1u; | ||||
/* Working pointer of inputA */ | ||||
pSrc1 = (pIn1 + srcALen) - (srcBLen - 1u); | ||||
px = pSrc1; | ||||
/* Working pointer of inputB */ | ||||
py = pIn2; | ||||
/* ------------------- | ||||
* Stage3 process | ||||
* ------------------*/ | ||||
while(blockSize3 > 0u) | ||||
{ | ||||
/* Accumulator is made zero for every iteration */ | ||||
sum = 0; | ||||
/* Apply loop unrolling and compute 4 MACs simultaneously. */ | ||||
k = count >> 2u; | ||||
/* First part of the processing with loop unrolling. Compute 4 MACs at a time. | ||||
** a second loop below computes MACs for the remaining 1 to 3 samples. */ | ||||
while(k > 0u) | ||||
{ | ||||
/* Perform the multiply-accumulates */ | ||||
/* sum += x[srcALen - srcBLen + 4] * y[3] , sum += x[srcALen - srcBLen + 3] * y[2] */ | ||||
sum = __SMLALD(*__SIMD32(px)++, *__SIMD32(py)++, sum); | ||||
/* sum += x[srcALen - srcBLen + 2] * y[1] , sum += x[srcALen - srcBLen + 1] * y[0] */ | ||||
sum = __SMLALD(*__SIMD32(px)++, *__SIMD32(py)++, sum); | ||||
/* Decrement the loop counter */ | ||||
k--; | ||||
} | ||||
/* If the count is not a multiple of 4, compute any remaining MACs here. | ||||
** No loop unrolling is used. */ | ||||
k = count % 0x4u; | ||||
while(k > 0u) | ||||
{ | ||||
/* Perform the multiply-accumulates */ | ||||
sum = __SMLALD(*px++, *py++, sum); | ||||
/* Decrement the loop counter */ | ||||
k--; | ||||
} | ||||
/* Store the result in the accumulator in the destination buffer. */ | ||||
*pOut = (q15_t) (__SSAT((sum >> 15), 16)); | ||||
/* Destination pointer is updated according to the address modifier, inc */ | ||||
pOut += inc; | ||||
/* Update the inputA and inputB pointers for next MAC calculation */ | ||||
px = ++pSrc1; | ||||
py = pIn2; | ||||
/* Decrement the MAC count */ | ||||
count--; | ||||
/* Decrement the loop counter */ | ||||
blockSize3--; | ||||
} | ||||
#else | ||||
/* Run the below code for Cortex-M0 */ | ||||
q15_t *pIn1 = pSrcA; /* inputA pointer */ | ||||
q15_t *pIn2 = pSrcB + (srcBLen - 1u); /* inputB pointer */ | ||||
q63_t sum; /* Accumulators */ | ||||
uint32_t i = 0u, j; /* loop counters */ | ||||
uint32_t inv = 0u; /* Reverse order flag */ | ||||
uint32_t tot = 0u; /* Length */ | ||||
/* The algorithm implementation is based on the lengths of the inputs. */ | ||||
/* srcB is always made to slide across srcA. */ | ||||
/* So srcBLen is always considered as shorter or equal to srcALen */ | ||||
/* But CORR(x, y) is reverse of CORR(y, x) */ | ||||
/* So, when srcBLen > srcALen, output pointer is made to point to the end of the output buffer */ | ||||
/* and a varaible, inv is set to 1 */ | ||||
/* If lengths are not equal then zero pad has to be done to make the two | ||||
* inputs of same length. But to improve the performance, we include zeroes | ||||
* in the output instead of zero padding either of the the inputs*/ | ||||
/* If srcALen > srcBLen, (srcALen - srcBLen) zeroes has to included in the | ||||
* starting of the output buffer */ | ||||
/* If srcALen < srcBLen, (srcALen - srcBLen) zeroes has to included in the | ||||
* ending of the output buffer */ | ||||
/* Once the zero padding is done the remaining of the output is calcualted | ||||
* using convolution but with the shorter signal time shifted. */ | ||||
/* Calculate the length of the remaining sequence */ | ||||
tot = ((srcALen + srcBLen) - 2u); | ||||
if(srcALen > srcBLen) | ||||
{ | ||||
/* Calculating the number of zeros to be padded to the output */ | ||||
j = srcALen - srcBLen; | ||||
/* Initialise the pointer after zero padding */ | ||||
pDst += j; | ||||
} | ||||
else if(srcALen < srcBLen) | ||||
{ | ||||
/* Initialization to inputB pointer */ | ||||
pIn1 = pSrcB; | ||||
/* Initialization to the end of inputA pointer */ | ||||
pIn2 = pSrcA + (srcALen - 1u); | ||||
/* Initialisation of the pointer after zero padding */ | ||||
pDst = pDst + tot; | ||||
/* Swapping the lengths */ | ||||
j = srcALen; | ||||
srcALen = srcBLen; | ||||
srcBLen = j; | ||||
/* Setting the reverse flag */ | ||||
inv = 1; | ||||
} | ||||
/* Loop to calculate convolution for output length number of times */ | ||||
for (i = 0u; i <= tot; i++) | ||||
{ | ||||
/* Initialize sum with zero to carry on MAC operations */ | ||||
sum = 0; | ||||
/* Loop to perform MAC operations according to convolution equation */ | ||||
for (j = 0u; j <= i; j++) | ||||
{ | ||||
/* Check the array limitations */ | ||||
if((((i - j) < srcBLen) && (j < srcALen))) | ||||
{ | ||||
/* z[i] += x[i-j] * y[j] */ | ||||
sum += ((q31_t) pIn1[j] * pIn2[-((int32_t) i - j)]); | ||||
} | ||||
} | ||||
/* Store the output in the destination buffer */ | ||||
if(inv == 1) | ||||
*pDst-- = (q15_t) __SSAT((sum >> 15u), 16u); | ||||
else | ||||
*pDst++ = (q15_t) __SSAT((sum >> 15u), 16u); | ||||
} | ||||
#endif /* #ifndef ARM_MATH_CM0 */ | ||||
} | ||||
/** | ||||
* @} end of Corr group | ||||
*/ | ||||