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