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arm_correlate_fast_q31.c
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/ lib / src / stm32f4 / CPU / CMSIS / DSP_Lib / Source / FilteringFunctions / arm_correlate_fast_q31.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_q31.c
*
* Description: Fast Q31 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 Q31 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.
*
* @details
* <b>Scaling and Overflow Behavior:</b>
*
* \par
* This function is optimized for speed at the expense of fixed-point precision and overflow protection.
* The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format.
* These intermediate results are accumulated in a 32-bit register in 2.30 format.
* Finally, the accumulator is saturated and converted to a 1.31 result.
*
* \par
* The fast version has the same overflow behavior as the standard version but provides less precision since it discards the low 32 bits of each multiplication result.
* In order to avoid overflows completely the input signals must be scaled down.
* The input signals should be scaled down to avoid intermediate overflows.
* Scale down one of the inputs by 1/min(srcALen, srcBLen)to avoid overflows since a
* maximum of min(srcALen, srcBLen) number of additions is carried internally.
*
* \par
* See <code>arm_correlate_q31()</code> for a slower implementation of this function which uses 64-bit accumulation to provide higher precision.
*/
void arm_correlate_fast_q31(
q31_t * pSrcA,
uint32_t srcALen,
q31_t * pSrcB,
uint32_t srcBLen,
q31_t * pDst)
{
q31_t *pIn1; /* inputA pointer */
q31_t *pIn2; /* inputB pointer */
q31_t *pOut = pDst; /* output pointer */
q31_t *px; /* Intermediate inputA pointer */
q31_t *py; /* Intermediate inputB pointer */
q31_t *pSrc1; /* Intermediate pointers */
q31_t sum, acc0, acc1, acc2, acc3; /* Accumulators */
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 */
/* 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 */
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 stage 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] */
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* x[1] * y[srcBLen - 3] */
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* x[2] * y[srcBLen - 2] */
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* x[3] * y[srcBLen - 1] */
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* 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 = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* Decrement the loop counter */
k--;
}
/* Store the result in the accumulator in the destination buffer. */
*pOut = sum << 1;
/* 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;
/* count is index by which the pointer pIn1 to be incremented */
count = 1u;
/* -------------------
* 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 */
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], x[2] samples */
x0 = *(px++);
x1 = *(px++);
x2 = *(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 y[0] sample */
c0 = *(py++);
/* Read x[3] sample */
x3 = *(px++);
/* Perform the multiply-accumulate */
/* acc0 += x[0] * y[0] */
acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
/* acc1 += x[1] * y[0] */
acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
/* acc2 += x[2] * y[0] */
acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x2 * c0)) >> 32);
/* acc3 += x[3] * y[0] */
acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x3 * c0)) >> 32);
/* Read y[1] sample */
c0 = *(py++);
/* Read x[4] sample */
x0 = *(px++);
/* Perform the multiply-accumulates */
/* acc0 += x[1] * y[1] */
acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x1 * c0)) >> 32);
/* acc1 += x[2] * y[1] */
acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x2 * c0)) >> 32);
/* acc2 += x[3] * y[1] */
acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x3 * c0)) >> 32);
/* acc3 += x[4] * y[1] */
acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x0 * c0)) >> 32);
/* Read y[2] sample */
c0 = *(py++);
/* Read x[5] sample */
x1 = *(px++);
/* Perform the multiply-accumulates */
/* acc0 += x[2] * y[2] */
acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x2 * c0)) >> 32);
/* acc1 += x[3] * y[2] */
acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x3 * c0)) >> 32);
/* acc2 += x[4] * y[2] */
acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x0 * c0)) >> 32);
/* acc3 += x[5] * y[2] */
acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x1 * c0)) >> 32);
/* Read y[3] sample */
c0 = *(py++);
/* Read x[6] sample */
x2 = *(px++);
/* Perform the multiply-accumulates */
/* acc0 += x[3] * y[3] */
acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x3 * c0)) >> 32);
/* acc1 += x[4] * y[3] */
acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x0 * c0)) >> 32);
/* acc2 += x[5] * y[3] */
acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x1 * c0)) >> 32);
/* acc3 += x[6] * y[3] */
acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x2 * c0)) >> 32);
} while(--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)
{
/* Read y[4] sample */
c0 = *(py++);
/* Read x[7] sample */
x3 = *(px++);
/* Perform the multiply-accumulates */
/* acc0 += x[4] * y[4] */
acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
/* acc1 += x[5] * y[4] */
acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
/* acc2 += x[6] * y[4] */
acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x2 * c0)) >> 32);
/* acc3 += x[7] * y[4] */
acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x3 * c0)) >> 32);
/* Reuse the present samples for the next MAC */
x0 = x1;
x1 = x2;
x2 = x3;
/* Decrement the loop counter */
k--;
}
/* Store the result in the accumulator in the destination buffer. */
*pOut = (q31_t) (acc0 << 1);
/* Destination pointer is updated according to the address modifier, inc */
pOut += inc;
*pOut = (q31_t) (acc1 << 1);
pOut += inc;
*pOut = (q31_t) (acc2 << 1);
pOut += inc;
*pOut = (q31_t) (acc3 << 1);
pOut += inc;
/* Update the inputA and inputB pointers for next MAC calculation */
px = pIn1 + (count * 4u);
py = pIn2;
/* Increment the pointer pIn1 index, count by 1 */
count++;
/* 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) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* 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-accumulate */
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* Decrement the loop counter */
k--;
}
/* Store the result in the accumulator in the destination buffer. */
*pOut = sum << 1;
/* Destination pointer is updated according to the address modifier, inc */
pOut += inc;
/* Update the inputA and inputB pointers for next MAC calculation */
px = pIn1 + count;
py = pIn2;
/* Increment the MAC count */
count++;
/* 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) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* Decrement the loop counter */
k--;
}
/* Store the result in the accumulator in the destination buffer. */
*pOut = sum << 1;
/* Destination pointer is updated according to the address modifier, inc */
pOut += inc;
/* Update the inputA and inputB pointers for next MAC calculation */
px = pIn1 + count;
py = pIn2;
/* Increment the MAC count */
count++;
/* 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 = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* sum += x[srcALen - srcBLen + 3] * y[2] */
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* sum += x[srcALen - srcBLen + 2] * y[1] */
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* sum += x[srcALen - srcBLen + 1] * y[0] */
sum = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* 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 = (q31_t) ((((q63_t) sum << 32) +
((q63_t) * px++ * (*py++))) >> 32);
/* Decrement the loop counter */
k--;
}
/* Store the result in the accumulator in the destination buffer. */
*pOut = sum << 1;
/* 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
*/