text: /* ----------------------------------------------------------------------
   * Project:      CMSIS DSP Library
   * Title:        arm_conv_partial_f32.c
   * Description:  Partial convolution of floating-point sequences
   *
   * $Date:        18. March 2019
   * $Revision:    V1.6.0
   *
   * Target Processor: Cortex-M cores
   * -------------------------------------------------------------------- */
  /*
   * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
   *
   * SPDX-License-Identifier: Apache-2.0
   *
   * Licensed under the Apache License, Version 2.0 (the License); you may
   * not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an AS IS BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #include "dsp/filtering_functions.h"
  
  /**
    @ingroup groupFilters
   */
  
  /**
    @defgroup PartialConv Partial Convolution
  
    Partial Convolution is equivalent to Convolution except that a subset of the output samples is generated.
    Each function has two additional arguments.
    <code>firstIndex</code> specifies the starting index of the subset of output samples.
    <code>numPoints</code> is the number of output samples to compute.
    The function computes the output in the range
    <code>[firstIndex, ..., firstIndex+numPoints-1]</code>.
    The output array <code>pDst</code> contains <code>numPoints</code> values.
  
    The allowable range of output indices is [0 srcALen+srcBLen-2].
    If the requested subset does not fall in this range then the functions return ARM_MATH_ARGUMENT_ERROR.
    Otherwise the functions return ARM_MATH_SUCCESS.
    \note Refer to \ref arm_conv_f32() for details on fixed point behavior.
  
    @par           Fast Versions
                     Fast versions are supported for Q31 and Q15 of partial convolution.
                     Cycles for Fast versions are less compared to Q31 and Q15 of partial conv and the design requires
                     the input signals should be scaled down to avoid intermediate overflows.
  
    @par           Opt Versions
                     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 partial convolution
   */
  
  /**
    @addtogroup PartialConv
    @{
   */
  
  /**
    @brief         Partial convolution 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
    @param[in]     firstIndex  is the first output sample to start with
    @param[in]     numPoints   is the number of output points to be computed
    @return        execution status
                     - \ref ARM_MATH_SUCCESS        : Operation successful
                     - \ref ARM_MATH_ARGUMENT_ERROR : requested subset is not in the range [0 srcALen+srcBLen-2]
   */
  
  arm_status arm_conv_partial_f32(
    const float32_t * pSrcA,
          uint32_t srcALen,
    const float32_t * pSrcB,
          uint32_t srcBLen,
          float32_t * pDst,
          uint32_t firstIndex,
          uint32_t numPoints)
  {
  #if defined (ARM_MATH_DSP)
    const float32_t *pIn1 = pSrcA;                       /* InputA pointer */
    const float32_t *pIn2 = pSrcB;                       /* InputB pointer */
          float32_t *pOut = pDst;                        /* Output pointer */
    const float32_t *px;                                 /* Intermediate inputA pointer */
    const float32_t *py;                                 /* Intermediate inputB pointer */
    const float32_t *pSrc1, *pSrc2;                      /* Intermediate pointers */
          float32_t sum;                                 /* Accumulator */
          uint32_t j, k, count, blkCnt, check;
          uint32_t blockSize1, blockSize2, blockSize3;    /* Loop counters */
          arm_status status;                             /* Status of Partial convolution */
  
  #if defined (ARM_MATH_LOOPUNROLL)
          float32_t acc0, acc1, acc2, acc3;              /* Accumulator */
          float32_t x0, x1, x2, x3, c0;                  /* Temporary variables */
  #endif
  
    /* Check for range of output samples to be calculated */
    if ((firstIndex + numPoints) > ((srcALen + (srcBLen - 1U))))
    {
      /* Set status as ARM_MATH_ARGUMENT_ERROR */
      status = ARM_MATH_ARGUMENT_ERROR;
    }
    else
    {
      /* 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;
      }
      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;
      }
  
      /* Conditions to check which loopCounter holds
       * the first and last indices of the output samples to be calculated. */
      check = firstIndex + numPoints;
      blockSize3 = ((int32_t)check > (int32_t)srcALen) ? (int32_t)check - (int32_t)srcALen : 0;
      blockSize3 = ((int32_t)firstIndex > (int32_t)srcALen - 1) ? blockSize3 - (int32_t)firstIndex + (int32_t)srcALen : blockSize3;
      blockSize1 = ((int32_t) srcBLen - 1) - (int32_t) firstIndex;
      blockSize1 = (blockSize1 > 0) ? ((check > (srcBLen - 1U)) ? blockSize1 : numPoints) : 0;
      blockSize2 = ((int32_t) check - blockSize3) - (blockSize1 + (int32_t) firstIndex);
      blockSize2 = (blockSize2 > 0) ? blockSize2 : 0;
  
      /* conv(x,y) at n = x[n] * y[0] + x[n-1] * y[1] + x[n-2] * y[2] + ...+ x[n-N+1] * y[N -1] */
      /* The function is internally
       * divided into three stages according to the number of multiplications that has to be
       * taken place between inputA samples and inputB samples. In the first stage of the
       * algorithm, the multiplications increase by one for every iteration.
       * In the second stage of the algorithm, srcBLen number of multiplications are done.
       * In the third stage of the algorithm, the multiplications decrease by one
       * for every iteration. */
  
      /* Set the output pointer to point to the firstIndex
       * of the output sample to be calculated. */
      pOut = pDst + firstIndex;
  
      /* --------------------------
       * Initializations of stage1
       * -------------------------*/
  
      /* sum = x[0] * y[0]
       * sum = x[0] * y[1] + x[1] * y[0]
       * ....
       * sum = x[0] * y[srcBlen - 1] + x[1] * y[srcBlen - 2] +...+ x[srcBLen - 1] * y[0]
       */
  
      /* In this stage the MAC operations are increased by 1 for every iteration.
         The count variable holds the number of MAC operations performed.
         Since the partial convolution starts from firstIndex
         Number of Macs to be performed is firstIndex + 1 */
      count = 1U + firstIndex;
  
      /* Working pointer of inputA */
      px = pIn1;
  
      /* Working pointer of inputB */
      pSrc1 = pIn2 + firstIndex;
      py = pSrc1;
  
      /* ------------------------
       * Stage1 process
       * ----------------------*/
  
      /* The first stage starts here */
      while (blockSize1 > 0U)
      {
        /* Accumulator is made zero for every iteration */
        sum = 0.0f;
  
  #if defined (ARM_MATH_LOOPUNROLL)
  
        /* Loop unrolling: Compute 4 outputs at a time */
        k = count >> 2U;
  
        while (k > 0U)
        {
          /* x[0] * y[srcBLen - 1] */
          sum += *px++ * *py--;
  
          /* x[1] * y[srcBLen - 2] */
          sum += *px++ * *py--;
  
          /* x[2] * y[srcBLen - 3] */
          sum += *px++ * *py--;
  
          /* x[3] * y[srcBLen - 4] */
          sum += *px++ * *py--;
  
          /* Decrement loop counter */
          k--;
        }
  
        /* Loop unrolling: Compute remaining outputs */
        k = count % 0x4U;
  
  #else
  
        /* Initialize k with number of samples */
        k = count;
  
  #endif /* #if defined (ARM_MATH_LOOPUNROLL) */
  
        while (k > 0U)
        {
          /* Perform the multiply-accumulate */
          sum += *px++ * *py--;
  
          /* Decrement loop counter */
          k--;
        }
  
        /* Store the result in the accumulator in the destination buffer. */
        *pOut++ = sum;
  
        /* Update the inputA and inputB pointers for next MAC calculation */
        py = ++pSrc1;
        px = pIn1;
  
        /* Increment MAC count */
        count++;
  
        /* Decrement loop counter */
        blockSize1--;
      }
  
      /* --------------------------
       * Initializations of stage2
       * ------------------------*/
  
      /* sum = x[0] * y[srcBLen-1] + x[1] * y[srcBLen-2] +...+ x[srcBLen-1] * y[0]
       * sum = x[1] * y[srcBLen-1] + x[2] * y[srcBLen-2] +...+ x[srcBLen] * y[0]
       * ....
       * sum = x[srcALen-srcBLen-2] * y[srcBLen-1] + x[srcALen] * y[srcBLen-2] +...+ x[srcALen-1] * y[0]
       */
  
      /* Working pointer of inputA */
      if ((int32_t)firstIndex - (int32_t)srcBLen + 1 > 0)
      {
        pSrc1 = pIn1 + firstIndex - srcBLen + 1;
      }
      else
      {
        pSrc1 = pIn1;
      }
      px = pSrc1;
  
      /* Working pointer of inputB */
      pSrc2 = pIn2 + (srcBLen - 1U);
      py = pSrc2;
  
      /* 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 */
      if (srcBLen >= 4U)
      {
  #if defined (ARM_MATH_LOOPUNROLL)
  
        /* Loop unrolling: Compute 4 outputs at a time */
        blkCnt = ((uint32_t) 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[srcBLen - 1] sample */
            c0 = *py--;
            /* Read x[3] sample */
            x3 = *px++;
  
            /* Perform the multiply-accumulate */
            /* acc0 +=  x[0] * y[srcBLen - 1] */
            acc0 += x0 * c0;
            /* acc1 +=  x[1] * y[srcBLen - 1] */
            acc1 += x1 * c0;
            /* acc2 +=  x[2] * y[srcBLen - 1] */
            acc2 += x2 * c0;
            /* acc3 +=  x[3] * y[srcBLen - 1] */
            acc3 += x3 * c0;
  
            /* Read y[srcBLen - 2] sample */
            c0 = *py--;
            /* Read x[4] sample */
            x0 = *px++;
  
            /* Perform the multiply-accumulate */
            /* acc0 +=  x[1] * y[srcBLen - 2] */
            acc0 += x1 * c0;
            /* acc1 +=  x[2] * y[srcBLen - 2] */
            acc1 += x2 * c0;
            /* acc2 +=  x[3] * y[srcBLen - 2] */
            acc2 += x3 * c0;
            /* acc3 +=  x[4] * y[srcBLen - 2] */
            acc3 += x0 * c0;
  
            /* Read y[srcBLen - 3] sample */
            c0 = *py--;
            /* Read x[5] sample */
            x1 = *px++;
  
            /* Perform the multiply-accumulate */
            /* acc0 +=  x[2] * y[srcBLen - 3] */
            acc0 += x2 * c0;
            /* acc1 +=  x[3] * y[srcBLen - 2] */
            acc1 += x3 * c0;
            /* acc2 +=  x[4] * y[srcBLen - 2] */
            acc2 += x0 * c0;
            /* acc3 +=  x[5] * y[srcBLen - 2] */
            acc3 += x1 * c0;
  
            /* Read y[srcBLen - 4] sample */
            c0 = *py--;
            /* Read x[6] sample */
            x2 = *px++;
  
            /* Perform the multiply-accumulate */
            /* acc0 +=  x[3] * y[srcBLen - 4] */
            acc0 += x3 * c0;
            /* acc1 +=  x[4] * y[srcBLen - 4] */
            acc1 += x0 * c0;
            /* acc2 +=  x[5] * y[srcBLen - 4] */
            acc2 += x1 * c0;
            /* acc3 +=  x[6] * y[srcBLen - 4] */
            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[srcBLen - 5] sample */
            c0 = *py--;
            /* Read x[7] sample */
            x3 = *px++;
  
            /* Perform the multiply-accumulates */
            /* acc0 +=  x[4] * y[srcBLen - 5] */
            acc0 += x0 * c0;
            /* acc1 +=  x[5] * y[srcBLen - 5] */
            acc1 += x1 * c0;
            /* acc2 +=  x[6] * y[srcBLen - 5] */
            acc2 += x2 * c0;
            /* acc3 +=  x[7] * y[srcBLen - 5] */
            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;
          *pOut++ = acc1;
          *pOut++ = acc2;
          *pOut++ = acc3;
  
          /* Increment the pointer pIn1 index, count by 4 */
          count += 4U;
  
          /* Update the inputA and inputB pointers for next MAC calculation */
          px = pSrc1 + count;
          py = pSrc2;
  
          /* Decrement loop counter */
          blkCnt--;
        }
  
        /* Loop unrolling: Compute remaining outputs */
        blkCnt = (uint32_t) blockSize2 % 0x4U;
  
  #else
  
        /* Initialize blkCnt with number of samples */
        blkCnt = blockSize2;
  
  #endif /* #if defined (ARM_MATH_LOOPUNROLL) */
  
        while (blkCnt > 0U)
        {
          /* Accumulator is made zero for every iteration */
          sum = 0.0f;
  
  #if defined (ARM_MATH_LOOPUNROLL)
  
          /* Loop unrolling: Compute 4 outputs at a time */
          k = srcBLen >> 2U;
  
          while (k > 0U)
          {
            /* Perform the multiply-accumulates */
            sum += *px++ * *py--;
            sum += *px++ * *py--;
            sum += *px++ * *py--;
            sum += *px++ * *py--;
  
            /* Decrement loop counter */
            k--;
          }
  
          /* Loop unrolling: Compute remaining outputs */
          k = srcBLen % 0x4U;
  
  #else
  
          /* Initialize blkCnt with number of samples */
          k = srcBLen;
  
  #endif /* #if defined (ARM_MATH_LOOPUNROLL) */
  
          while (k > 0U)
          {
            /* Perform the multiply-accumulate */
            sum += *px++ * *py--;
  
            /* Decrement loop counter */
            k--;
          }
  
          /* Store the result in the accumulator in the destination buffer. */
          *pOut++ = sum;
  
          /* Increment MAC count */
          count++;
  
          /* Update the inputA and inputB pointers for next MAC calculation */
          px = pSrc1 + count;
          py = pSrc2;
  
          /* Decrement loop counter */
          blkCnt--;
        }
      }
      else
      {
        /* If the srcBLen is not a multiple of 4,
         * the blockSize2 loop cannot be unrolled by 4 */
        blkCnt = (uint32_t) blockSize2;
  
        while (blkCnt > 0U)
        {
          /* Accumulator is made zero for every iteration */
          sum = 0.0f;
  
          /* srcBLen number of MACS should be performed */
          k = srcBLen;
  
          while (k > 0U)
          {
            /* Perform the multiply-accumulate */
            sum += *px++ * *py--;
  
            /* Decrement loop counter */
            k--;
          }
  
          /* Store the result in the accumulator in the destination buffer. */
          *pOut++ = sum;
  
          /* Increment the MAC count */
          count++;
  
          /* Update the inputA and inputB pointers for next MAC calculation */
          px = pSrc1 + count;
          py = pSrc2;
  
          /* Decrement the loop counter */
          blkCnt--;
        }
      }
  
  
      /* --------------------------
       * Initializations of stage3
       * -------------------------*/
  
      /* sum += x[srcALen-srcBLen+1] * y[srcBLen-1] + x[srcALen-srcBLen+2] * y[srcBLen-2] +...+ x[srcALen-1] * y[1]
       * sum += x[srcALen-srcBLen+2] * y[srcBLen-1] + x[srcALen-srcBLen+3] * y[srcBLen-2] +...+ x[srcALen-1] * y[2]
       * ....
       * sum +=  x[srcALen-2] * y[srcBLen-1] + x[srcALen-1] * y[srcBLen-2]
       * sum +=  x[srcALen-1] * y[srcBLen-1]
       */
  
      /* In this stage the MAC operations are decreased by 1 for every iteration.
         The blockSize3 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 */
      pSrc2 = pIn2 + (srcBLen - 1U);
      py = pSrc2;
  
      /* -------------------
       * Stage3 process
       * ------------------*/
  
      while (blockSize3 > 0U)
      {
        /* Accumulator is made zero for every iteration */
        sum = 0.0f;
  
  #if defined (ARM_MATH_LOOPUNROLL)
  
        /* Loop unrolling: Compute 4 outputs at a time */
        k = count >> 2U;
  
        while (k > 0U)
        {
          /* sum += x[srcALen - srcBLen + 1] * y[srcBLen - 1] */
          sum += *px++ * *py--;
  
          /* sum += x[srcALen - srcBLen + 2] * y[srcBLen - 2] */
          sum += *px++ * *py--;
  
          /* sum += x[srcALen - srcBLen + 3] * y[srcBLen - 3] */
          sum += *px++ * *py--;
  
          /* sum += x[srcALen - srcBLen + 4] * y[srcBLen - 4] */
          sum += *px++ * *py--;
  
          /* Decrement loop counter */
          k--;
        }
  
        /* Loop unrolling: Compute remaining outputs */
        k = count % 0x4U;
  
  #else
  
        /* Initialize blkCnt with number of samples */
        k = count;
  
  #endif /* #if defined (ARM_MATH_LOOPUNROLL) */
  
        while (k > 0U)
        {
          /* Perform the multiply-accumulate */
          /* sum +=  x[srcALen-1] * y[srcBLen-1] */
          sum += *px++ * *py--;
  
          /* Decrement loop counter */
          k--;
        }
  
        /* Store the result in the accumulator in the destination buffer. */
        *pOut++ = sum;
  
        /* Update the inputA and inputB pointers for next MAC calculation */
        px = ++pSrc1;
        py = pSrc2;
  
        /* Decrement MAC count */
        count--;
  
        /* Decrement the loop counter */
        blockSize3--;
      }
  
      /* Set status as ARM_MATH_SUCCESS */
      status = ARM_MATH_SUCCESS;
    }
  
    /* Return to application */
    return (status);
  
  #else
  /* alternate version for CM0_FAMILY */
  
    const float32_t *pIn1 = pSrcA;                       /* InputA pointer */
    const float32_t *pIn2 = pSrcB;                       /* InputB pointer */
          float32_t sum;                                 /* Accumulator */
          uint32_t i, j;                                 /* Loop counters */
          arm_status status;                             /* Status of Partial convolution */
  
    /* Check for range of output samples to be calculated */
    if ((firstIndex + numPoints) > ((srcALen + (srcBLen - 1U))))
    {
      /* Set status as ARM_MATH_ARGUMENT_ERROR */
      status = ARM_MATH_ARGUMENT_ERROR;
    }
    else
    {
      /* Loop to calculate convolution for output length number of values */
      for (i = firstIndex; i <= (firstIndex + numPoints - 1); 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[i - j]);
          }
        }
  
        /* Store the output in the destination buffer */
        pDst[i] = sum;
      }
  
      /* Set status as ARM_SUCCESS */
      status = ARM_MATH_SUCCESS;
    }
  
    /* Return to application */
    return (status);
  
  #endif /* defined(ARM_MATH_DSP) */
  }
  
  /**
    @} end of PartialConv group
   */
  