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# arm_power_q31.c

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    00001 /* ----------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        29. November 2010
    00005 * $Revision:    V1.0.3
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_power_q31.c
    00009 *
    00010 * Description:  sum of the square of the elements in an array of Q31 type
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3
    00013 *
    00014 * Version 1.0.3 2010/11/29
    00015 *    Re-organized the CMSIS folders and updated documentation.
    00016 *
    00017 * Version 1.0.2 2010/11/11
    00018 *    Documentation updated.
    00019 *
    00020 * Version 1.0.1 2010/10/05
    00021 *    Production release and review comments incorporated.
    00022 *
    00023 * Version 1.0.0 2010/09/20
    00024 *    Production release and review comments incorporated.
    00025 * -------------------------------------------------------------------- */
    00026
    00027 #include "arm_math.h"
    00028
    00060 void arm_power_q31(
    00061   q31_t * pSrc,
    00062   uint32_t blockSize,
    00063   q63_t * pResult)
    00064 {
    00065   q63_t sum = 0;                                 /* Temporary result storage */
    00066   q31_t in;
    00067   uint32_t blkCnt;                               /* loop counter */
    00068
    00069
    00070   /*loop Unrolling */
    00071   blkCnt = blockSize >> 2u;
    00072
    00073   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00074    ** a second loop below computes the remaining 1 to 3 samples. */
    00075   while(blkCnt > 0u)
    00076   {
    00077     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
    00078     /* Compute Power then shift intermediate results by 14 bits to maintain 16.48 format and then store the result in a temporary variable sum, providing 15 guard bits. */
    00079     in = *pSrc++;
    00080     sum += ((q63_t) in * in) >> 14u;
    00081
    00082     in = *pSrc++;
    00083     sum += ((q63_t) in * in) >> 14u;
    00084
    00085     in = *pSrc++;
    00086     sum += ((q63_t) in * in) >> 14u;
    00087
    00088     in = *pSrc++;
    00089     sum += ((q63_t) in * in) >> 14u;
    00090
    00091     /* Decrement the loop counter */
    00092     blkCnt--;
    00093   }
    00094
    00095   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00096    ** No loop unrolling is used. */
    00097   blkCnt = blockSize % 0x4u;
    00098
    00099   while(blkCnt > 0u)
    00100   {
    00101     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */
    00102     /* Compute Power and then store the result in a temporary variable, sum. */
    00103     in = *pSrc++;
    00104     sum += ((q63_t) in * in) >> 14u;
    00105
    00106     /* Decrement the loop counter */
    00107     blkCnt--;
    00108   }
    00109
    00110   /* Store the results in 16.48 format  */
    00111   *pResult = sum;
    00112 }
    00113

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