text: /* ----------------------------------------------------------------------
  * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
  *
  * $Date: 16/10/14 6:01p $Revision:  V.1.4.5
  *
  * Project:      CMSIS DSP Library
  * Title:        arm_mat_mult_fast_q31.c
  *
  * Description:   Q31 matrix multiplication (fast variant).
  *
  * Target Processor: Cortex-M4/Cortex-M3
  *
  * 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 groupMatrix
   */
  
  /**
   * @addtogroup MatrixMult
   * @{
   */
  
  /**
   * @brief Q31 matrix multiplication (fast variant) for Cortex-M3 and Cortex-M4
   * @param[in]       *pSrcA points to the first input matrix structure
   * @param[in]       *pSrcB points to the second input matrix structure
   * @param[out]      *pDst points to output matrix structure
   * @return          The function returns either
   * <code>ARM_MATH_SIZE_MISMATCH</code> or <code>ARM_MATH_SUCCESS</code> based on the outcome of size checking.
   *
   * @details
   * <b>Scaling and Overflow Behavior:</b>
   *
   * \par
   * The difference between the function arm_mat_mult_q31() and this fast variant is that
   * the fast variant use a 32-bit rather than a 64-bit accumulator.
   * 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.
   * Scale down one of the input matrices by log2(numColsA) bits to
   * avoid overflows, as a total of numColsA additions are computed internally for each
   * output element.
   *
   * \par
   * See <code>arm_mat_mult_q31()</code> for a slower implementation of this function
   * which uses 64-bit accumulation to provide higher precision.
   */
  
  arm_status arm_mat_mult_fast_q31(
      const arm_matrix_instance_q31 * pSrcA,
      const arm_matrix_instance_q31 * pSrcB,
      arm_matrix_instance_q31 * pDst)
  {
      q31_t *pIn1 = pSrcA->pData;                    /* input data matrix pointer A */
      q31_t *pIn2 = pSrcB->pData;                    /* input data matrix pointer B */
      q31_t *pInA = pSrcA->pData;                    /* input data matrix pointer A */
  //  q31_t *pSrcB = pSrcB->pData;                    /* input data matrix pointer B */
      q31_t *pOut = pDst->pData;                     /* output data matrix pointer */
      q31_t *px;                                     /* Temporary output data matrix pointer */
      q31_t sum;                                     /* Accumulator */
      uint16_t numRowsA = pSrcA->numRows;            /* number of rows of input matrix A    */
      uint16_t numColsB = pSrcB->numCols;            /* number of columns of input matrix B */
      uint16_t numColsA = pSrcA->numCols;            /* number of columns of input matrix A */
      uint16_t col, i = 0u, j, row = numRowsA, colCnt;      /* loop counters */
      arm_status status;                             /* status of matrix multiplication */
      q31_t inA1, inA2, inA3, inA4, inB1, inB2, inB3, inB4;
  
  #ifdef ARM_MATH_MATRIX_CHECK
  
  
      /* Check for matrix mismatch condition */
      if((pSrcA->numCols != pSrcB->numRows) ||
              (pSrcA->numRows != pDst->numRows) || (pSrcB->numCols != pDst->numCols))
      {
          /* Set status as ARM_MATH_SIZE_MISMATCH */
          status = ARM_MATH_SIZE_MISMATCH;
      }
      else
  #endif /*      #ifdef ARM_MATH_MATRIX_CHECK    */
  
      {
          /* The following loop performs the dot-product of each row in pSrcA with each column in pSrcB */
          /* row loop */
          do
          {
              /* Output pointer is set to starting address of the row being processed */
              px = pOut + i;
  
              /* For every row wise process, the column loop counter is to be initiated */
              col = numColsB;
  
              /* For every row wise process, the pIn2 pointer is set
               ** to the starting address of the pSrcB data */
              pIn2 = pSrcB->pData;
  
              j = 0u;
  
              /* column loop */
              do
              {
                  /* Set the variable sum, that acts as accumulator, to zero */
                  sum = 0;
  
                  /* Initiate the pointer pIn1 to point to the starting address of pInA */
                  pIn1 = pInA;
  
                  /* Apply loop unrolling and compute 4 MACs simultaneously. */
                  colCnt = numColsA >> 2;
  
  
                  /* matrix multiplication */
                  while(colCnt > 0u)
                  {
                      /* c(m,n) = a(1,1)*b(1,1) + a(1,2) * b(2,1) + .... + a(m,p)*b(p,n) */
                      /* Perform the multiply-accumulates */
                      inB1 = *pIn2;
                      pIn2 += numColsB;
  
                      inA1 = pIn1[0];
                      inA2 = pIn1[1];
  
                      inB2 = *pIn2;
                      pIn2 += numColsB;
  
                      inB3 = *pIn2;
                      pIn2 += numColsB;
  
                      sum = (q31_t)((((q63_t) sum << 32) + ((q63_t) inA1 * inB1)) >> 32);
                      sum = (q31_t)((((q63_t) sum << 32) + ((q63_t) inA2 * inB2)) >> 32);
  
                      inA3 = pIn1[2];
                      inA4 = pIn1[3];
  
                      inB4 = *pIn2;
                      pIn2 += numColsB;
  
                      sum = (q31_t)((((q63_t) sum << 32) + ((q63_t) inA3 * inB3)) >> 32);
                      sum = (q31_t)((((q63_t) sum << 32) + ((q63_t) inA4 * inB4)) >> 32);
  
                      pIn1 += 4u;
  
                      /* Decrement the loop counter */
                      colCnt--;
                  }
  
                  /* If the columns of pSrcA is not a multiple of 4, compute any remaining output samples here.
                   ** No loop unrolling is used. */
                  colCnt = numColsA % 0x4u;
  
                  while(colCnt > 0u)
                  {
                      /* c(m,n) = a(1,1)*b(1,1) + a(1,2) * b(2,1) + .... + a(m,p)*b(p,n) */
                      /* Perform the multiply-accumulates */
                      sum = (q31_t)((((q63_t) sum << 32) +
                                     ((q63_t) * pIn1++ * (*pIn2))) >> 32);
                      pIn2 += numColsB;
  
                      /* Decrement the loop counter */
                      colCnt--;
                  }
  
                  /* Convert the result from 2.30 to 1.31 format and store in destination buffer */
                  *px++ = sum << 1;
  
                  /* Update the pointer pIn2 to point to the  starting address of the next column */
                  j++;
                  pIn2 = pSrcB->pData + j;
  
                  /* Decrement the column loop counter */
                  col--;
  
              }
              while(col > 0u);
  
              /* Update the pointer pInA to point to the  starting address of the next row */
              i = i + numColsB;
              pInA = pInA + numColsA;
  
              /* Decrement the row loop counter */
              row--;
  
          }
          while(row > 0u);
  
          /* set status as ARM_MATH_SUCCESS */
          status = ARM_MATH_SUCCESS;
      }
      /* Return to application */
      return (status);
  }
  
  /**
   * @} end of MatrixMult group
   */
  