pigweed / third_party / github / STMicroelectronics / cmsis_core / 7dd288b23bf605a3a2fafa81a29d2c96a2fd83ce / . / DSP_Lib / Source / FilteringFunctions / arm_correlate_f32.c

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

* Copyright (C) 2010-2014 ARM Limited. All rights reserved. | |

* | |

* $Date: 19. March 2015 | |

* $Revision: V.1.4.5 | |

* | |

* Project: CMSIS DSP Library | |

* Title: arm_correlate_f32.c | |

* | |

* Description: Correlation of floating-point sequences. | |

* | |

* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 | |

* | |

* Redistribution and use in source and binary forms, with or without | |

* modification, are permitted provided that the following conditions | |

* are met: | |

* - Redistributions of source code must retain the above copyright | |

* notice, this list of conditions and the following disclaimer. | |

* - Redistributions in binary form must reproduce the above copyright | |

* notice, this list of conditions and the following disclaimer in | |

* the documentation and/or other materials provided with the | |

* distribution. | |

* - Neither the name of ARM LIMITED nor the names of its contributors | |

* may be used to endorse or promote products derived from this | |

* software without specific prior written permission. | |

* | |

* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |

* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |

* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS | |

* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE | |

* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, | |

* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, | |

* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | |

* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER | |

* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |

* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN | |

* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | |

* POSSIBILITY OF SUCH DAMAGE. | |

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

#include "arm_math.h" | |

/** | |

* @ingroup groupFilters | |

*/ | |

/** | |

* @defgroup Corr Correlation | |

* | |

* Correlation is a mathematical operation that is similar to convolution. | |

* As with convolution, correlation uses two signals to produce a third signal. | |

* The underlying algorithms in correlation and convolution are identical except that one of the inputs is flipped in convolution. | |

* Correlation is commonly used to measure the similarity between two signals. | |

* It has applications in pattern recognition, cryptanalysis, and searching. | |

* The CMSIS library provides correlation functions for Q7, Q15, Q31 and floating-point data types. | |

* Fast versions of the Q15 and Q31 functions are also provided. | |

* | |

* \par Algorithm | |

* Let <code>a[n]</code> and <code>b[n]</code> be sequences of length <code>srcALen</code> and <code>srcBLen</code> samples respectively. | |

* The convolution of the two signals is denoted by | |

* <pre> | |

* c[n] = a[n] * b[n] | |

* </pre> | |

* In correlation, one of the signals is flipped in time | |

* <pre> | |

* c[n] = a[n] * b[-n] | |

* </pre> | |

* | |

* \par | |

* and this is mathematically defined as | |

* \image html CorrelateEquation.gif | |

* \par | |

* The <code>pSrcA</code> points to the first input vector of length <code>srcALen</code> and <code>pSrcB</code> points to the second input vector of length <code>srcBLen</code>. | |

* The result <code>c[n]</code> is of length <code>2 * max(srcALen, srcBLen) - 1</code> and is defined over the interval <code>n=0, 1, 2, ..., (2 * max(srcALen, srcBLen) - 2)</code>. | |

* The output result is written to <code>pDst</code> and the calling function must allocate <code>2 * max(srcALen, srcBLen) - 1</code> words for the result. | |

* | |

* <b>Note</b> | |

* \par | |

* The <code>pDst</code> should be initialized to all zeros before being used. | |

* | |

* <b>Fixed-Point Behavior</b> | |

* \par | |

* Correlation requires summing up a large number of intermediate products. | |

* As such, the Q7, Q15, and Q31 functions run a risk of overflow and saturation. | |

* Refer to the function specific documentation below for further details of the particular algorithm used. | |

* | |

* | |

* <b>Fast Versions</b> | |

* | |

* \par | |

* Fast versions are supported for Q31 and Q15. Cycles for Fast versions are less compared to Q31 and Q15 of correlate and the design requires | |

* the input signals should be scaled down to avoid intermediate overflows. | |

* | |

* | |

* <b>Opt Versions</b> | |

* | |

* \par | |

* Opt versions are supported for Q15 and Q7. Design uses internal scratch buffer for getting good optimisation. | |

* These versions are optimised in cycles and consumes more memory(Scratch memory) compared to Q15 and Q7 versions of correlate | |

*/ | |

/** | |

* @addtogroup Corr | |

* @{ | |

*/ | |

/** | |

* @brief Correlation of floating-point 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. | |

*/ | |

void arm_correlate_f32( | |

float32_t * pSrcA, | |

uint32_t srcALen, | |

float32_t * pSrcB, | |

uint32_t srcBLen, | |

float32_t * pDst) | |

{ | |

#ifndef ARM_MATH_CM0_FAMILY | |

/* Run the below code for Cortex-M4 and Cortex-M3 */ | |

float32_t *pIn1; /* inputA pointer */ | |

float32_t *pIn2; /* inputB pointer */ | |

float32_t *pOut = pDst; /* output pointer */ | |

float32_t *px; /* Intermediate inputA pointer */ | |

float32_t *py; /* Intermediate inputB pointer */ | |

float32_t *pSrc1; /* Intermediate pointers */ | |

float32_t sum, acc0, acc1, acc2, acc3; /* Accumulators */ | |

float32_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 counters */ | |

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 */ | |

/* 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 assume 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 has to be 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; | |

//while(j > 0u) | |

//{ | |

// /* Zero is stored in the destination buffer */ | |

// *pOut++ = 0.0f; | |

// /* Decrement the loop counter */ | |

// 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 = 0.0f; | |

/* 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) | |

{ | |

/* x[0] * y[srcBLen - 4] */ | |

sum += *px++ * *py++; | |

/* x[1] * y[srcBLen - 3] */ | |

sum += *px++ * *py++; | |

/* x[2] * y[srcBLen - 2] */ | |

sum += *px++ * *py++; | |

/* x[3] * y[srcBLen - 1] */ | |

sum += *px++ * *py++; | |

/* 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-accumulate */ | |

/* x[0] * y[srcBLen - 1] */ | |

sum += *px++ * *py++; | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* Store the result in the accumulator in the destination buffer. */ | |

*pOut = sum; | |

/* 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 = 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 = 0.0f; | |

acc1 = 0.0f; | |

acc2 = 0.0f; | |

acc3 = 0.0f; | |

/* 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 += x0 * c0; | |

/* acc1 += x[1] * y[0] */ | |

acc1 += x1 * c0; | |

/* acc2 += x[2] * y[0] */ | |

acc2 += x2 * c0; | |

/* acc3 += x[3] * y[0] */ | |

acc3 += x3 * c0; | |

/* Read y[1] sample */ | |

c0 = *(py++); | |

/* Read x[4] sample */ | |

x0 = *(px++); | |

/* Perform the multiply-accumulate */ | |

/* acc0 += x[1] * y[1] */ | |

acc0 += x1 * c0; | |

/* acc1 += x[2] * y[1] */ | |

acc1 += x2 * c0; | |

/* acc2 += x[3] * y[1] */ | |

acc2 += x3 * c0; | |

/* acc3 += x[4] * y[1] */ | |

acc3 += x0 * c0; | |

/* Read y[2] sample */ | |

c0 = *(py++); | |

/* Read x[5] sample */ | |

x1 = *(px++); | |

/* Perform the multiply-accumulates */ | |

/* acc0 += x[2] * y[2] */ | |

acc0 += x2 * c0; | |

/* acc1 += x[3] * y[2] */ | |

acc1 += x3 * c0; | |

/* acc2 += x[4] * y[2] */ | |

acc2 += x0 * c0; | |

/* acc3 += x[5] * y[2] */ | |

acc3 += x1 * c0; | |

/* Read y[3] sample */ | |

c0 = *(py++); | |

/* Read x[6] sample */ | |

x2 = *(px++); | |

/* Perform the multiply-accumulates */ | |

/* acc0 += x[3] * y[3] */ | |

acc0 += x3 * c0; | |

/* acc1 += x[4] * y[3] */ | |

acc1 += x0 * c0; | |

/* acc2 += x[5] * y[3] */ | |

acc2 += x1 * c0; | |

/* acc3 += x[6] * y[3] */ | |

acc3 += x2 * c0; | |

} 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 += x0 * c0; | |

/* acc1 += x[5] * y[4] */ | |

acc1 += x1 * c0; | |

/* acc2 += x[6] * y[4] */ | |

acc2 += x2 * c0; | |

/* acc3 += x[7] * y[4] */ | |

acc3 += x3 * c0; | |

/* 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 = acc0; | |

/* Destination pointer is updated according to the address modifier, inc */ | |

pOut += inc; | |

*pOut = acc1; | |

pOut += inc; | |

*pOut = acc2; | |

pOut += inc; | |

*pOut = acc3; | |

pOut += inc; | |

/* Increment the pointer pIn1 index, count by 4 */ | |

count += 4u; | |

/* Update the inputA and inputB pointers for next MAC calculation */ | |

px = pIn1 + count; | |

py = pIn2; | |

/* 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 = 0.0f; | |

/* 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 += *px++ * *py++; | |

sum += *px++ * *py++; | |

sum += *px++ * *py++; | |

sum += *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-accumulate */ | |

sum += *px++ * *py++; | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* Store the result in the accumulator in the destination buffer. */ | |

*pOut = sum; | |

/* 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 = 0.0f; | |

/* Loop over srcBLen */ | |

k = srcBLen; | |

while(k > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

sum += *px++ * *py++; | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* Store the result in the accumulator in the destination buffer. */ | |

*pOut = sum; | |

/* 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--; | |

} | |

} | |

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

* 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 = 0.0f; | |

/* 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 += *px++ * *py++; | |

/* sum += x[srcALen - srcBLen + 3] * y[2] */ | |

sum += *px++ * *py++; | |

/* sum += x[srcALen - srcBLen + 2] * y[1] */ | |

sum += *px++ * *py++; | |

/* sum += x[srcALen - srcBLen + 1] * y[0] */ | |

sum += *px++ * *py++; | |

/* 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 += *px++ * *py++; | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* Store the result in the accumulator in the destination buffer. */ | |

*pOut = sum; | |

/* 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 */ | |

float32_t *pIn1 = pSrcA; /* inputA pointer */ | |

float32_t *pIn2 = pSrcB + (srcBLen - 1u); /* inputB pointer */ | |

float32_t sum; /* Accumulator */ | |

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 assume 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 = 0.0f; | |

/* 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 += pIn1[j] * pIn2[-((int32_t) i - j)]; | |

} | |

} | |

/* Store the output in the destination buffer */ | |

if(inv == 1) | |

*pDst-- = sum; | |

else | |

*pDst++ = sum; | |

} | |

#endif /* #ifndef ARM_MATH_CM0_FAMILY */ | |

} | |

/** | |

* @} end of Corr group | |

*/ |