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arm_correlate_fast_q15.c
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/ lib / src / stm32f4 / CPU / CMSIS / DSP_Lib / Source / FilteringFunctions / arm_correlate_fast_q15.c
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/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date: 15. July 2011
* $Revision: V1.0.10
*
* Project: CMSIS DSP Library
* Title: arm_correlate_fast_q15.c
*
* Description: Fast Q15 Correlation.
*
* Target Processor: Cortex-M4/Cortex-M3
*
* 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 groupFilters
*/
/**
* @addtogroup Corr
* @{
*/
/**
* @brief Correlation of Q15 sequences (fast version) for Cortex-M3 and Cortex-M4.
* @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.
*
* <b>Scaling and Overflow Behavior:</b>
*
* \par
* This fast version uses a 32-bit accumulator with 2.30 format.
* The accumulator maintains full precision of the intermediate multiplication results but provides only a single guard bit.
* There is no saturation on intermediate additions.
* Thus, if the accumulator overflows it wraps around and distorts the result.
* The input signals should be scaled down to avoid intermediate overflows.
* Scale down one of the inputs by 1/min(srcALen, srcBLen) to avoid overflow since a
* maximum of min(srcALen, srcBLen) number of additions is carried internally.
* The 2.30 accumulator is right shifted by 15 bits and then saturated to 1.15 format to yield the final result.
*
* \par
* See <code>arm_correlate_q15()</code> for a slower implementation of this function which uses a 64-bit accumulator to avoid wrap around distortion.
*/
void arm_correlate_fast_q15(
q15_t * pSrcA,
uint32_t srcALen,
q15_t * pSrcB,
uint32_t srcBLen,
q15_t * pDst)
{
q15_t *pIn1; /* inputA pointer */
q15_t *pIn2; /* inputB pointer */
q15_t *pOut = pDst; /* output pointer */
q31_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 = __SMLAD(*__SIMD32(px)++, *__SIMD32(py)++, sum);
/* x[3] * y[srcBLen - 1] , x[2] * y[srcBLen - 2] */
sum = __SMLAD(*__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 = __SMLAD(*px++, *py++, sum);
/* Decrement the loop counter */
k--;
}
/* Store the result in the accumulator in the destination buffer. */
*pOut = (q15_t) (sum >> 15);
/* 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 = __SMLAD(x0, c0, acc0);
/* acc1 += x[1] * y[0] + x[2] * y[1] */
acc1 = __SMLAD(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 = __SMLAD(x2, c0, acc2);
/* acc3 += x[3] * y[0] + x[4] * y[1] */
acc3 = __SMLAD(x3, c0, acc3);
/* Read y[2] and y[3] */
c0 = *(pb++);
/* acc0 += x[2] * y[2] + x[3] * y[3] */
acc0 = __SMLAD(x2, c0, acc0);
/* acc1 += x[3] * y[2] + x[4] * y[3] */
acc1 = __SMLAD(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 = __SMLAD(x0, c0, acc2);
/* acc3 += x[5] * y[2] + x[6] * y[3] */
acc3 = __SMLAD(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 = __SMLAD(x0, c0, acc0);
acc1 = __SMLAD(x1, c0, acc1);
acc2 = __SMLADX(x1, c0, acc2);
acc3 = __SMLADX(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 = __SMLAD(x0, c0, acc0);
acc1 = __SMLAD(x1, c0, acc1);
acc2 = __SMLAD(x3, c0, acc2);
acc3 = __SMLAD(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 = __SMLAD(x0, c0, acc0);
acc1 = __SMLAD(x1, c0, acc1);
acc2 = __SMLAD(x3, c0, acc2);
acc3 = __SMLAD(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 = __SMLADX(x1, c0, acc0);
acc1 = __SMLAD(x2, c0, acc1);
acc2 = __SMLADX(x2, c0, acc2);
acc3 = __SMLADX(x3, c0, acc3);
}
/* Store the result in the accumulator in the destination buffer. */
*pOut = (q15_t) (acc0 >> 15);
/* Destination pointer is updated according to the address modifier, inc */
pOut += inc;
*pOut = (q15_t) (acc1 >> 15);
pOut += inc;
*pOut = (q15_t) (acc2 >> 15);
pOut += inc;
*pOut = (q15_t) (acc3 >> 15);
pOut += inc;
/* Increment the pointer pIn1 index, count by 1 */
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 += ((q31_t) * px++ * *py++);
sum += ((q31_t) * px++ * *py++);
sum += ((q31_t) * px++ * *py++);
sum += ((q31_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 += ((q31_t) * px++ * *py++);
/* Decrement the loop counter */
k--;
}
/* Store the result in the accumulator in the destination buffer. */
*pOut = (q15_t) (sum >> 15);
/* Destination pointer is updated according to the address modifier, inc */
pOut += inc;
/* Increment the pointer pIn1 index, count by 1 */
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 += ((q31_t) * px++ * *py++);
/* Decrement the loop counter */
k--;
}
/* Store the result in the accumulator in the destination buffer. */
*pOut = (q15_t) (sum >> 15);
/* 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 = __SMLAD(*__SIMD32(px)++, *__SIMD32(py)++, sum);
/* sum += x[srcALen - srcBLen + 2] * y[1] , sum += x[srcALen - srcBLen + 1] * y[0] */
sum = __SMLAD(*__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 = __SMLAD(*px++, *py++, sum);
/* Decrement the loop counter */
k--;
}
/* Store the result in the accumulator in the destination buffer. */
*pOut = (q15_t) (sum >> 15);
/* 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--;
}
}
/**
* @} end of Corr group
*/