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Diffstat (limited to 'platform/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c')
| -rw-r--r-- | platform/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/platform/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c b/platform/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c new file mode 100644 index 0000000..4815ff2 --- /dev/null +++ b/platform/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c @@ -0,0 +1,186 @@ +/* ---------------------------------------------------------------------- +* Copyright (C) 2010-2014 ARM Limited. All rights reserved. +* +* $Date: 12. March 2014 +* $Revision: V1.4.4 +* +* Project: CMSIS DSP Library +* Title: arm_std_q31.c +* +* Description: Standard deviation of an array of Q31 type. +* +* 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 groupStats + */ + +/** + * @addtogroup STD + * @{ + */ + + +/** + * @brief Standard deviation of the elements of a Q31 vector. + * @param[in] *pSrc points to the input vector + * @param[in] blockSize length of the input vector + * @param[out] *pResult standard deviation value returned here + * @return none. + * @details + * <b>Scaling and Overflow Behavior:</b> + * + *\par + * The function is implemented using an internal 64-bit accumulator. + * The input is represented in 1.31 format, which is then downshifted by 8 bits + * which yields 1.23, and intermediate multiplication yields a 2.46 format. + * The accumulator maintains full precision of the intermediate multiplication results, + * but provides only a 16 guard bits. + * There is no saturation on intermediate additions. + * If the accumulator overflows it wraps around and distorts the result. + * In order to avoid overflows completely the input signal must be scaled down by + * log2(blockSize)-8 bits, as a total of blockSize additions are performed internally. + * After division, internal variables should be Q18.46 + * Finally, the 18.46 accumulator is right shifted by 15 bits to yield a 1.31 format value. + * + */ + + +void arm_std_q31( + q31_t * pSrc, + uint32_t blockSize, + q31_t * pResult) +{ + q63_t sum = 0; /* Accumulator */ + q63_t meanOfSquares, squareOfMean; /* square of mean and mean of square */ + q31_t in; /* input value */ + uint32_t blkCnt; /* loop counter */ + q63_t sumOfSquares = 0; /* Accumulator */ + + if(blockSize == 1) + { + *pResult = 0; + return; + } + +#ifndef ARM_MATH_CM0_FAMILY + + /* Run the below code for Cortex-M4 and Cortex-M3 */ + + /*loop Unrolling */ + blkCnt = blockSize >> 2u; + + /* First part of the processing with loop unrolling. Compute 4 outputs at a time. + ** a second loop below computes the remaining 1 to 3 samples. */ + while(blkCnt > 0u) + { + /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */ + /* Compute Sum of squares of the input samples + * and then store the result in a temporary variable, sum. */ + in = *pSrc++ >> 8; + sum += in; + sumOfSquares += ((q63_t) (in) * (in)); + in = *pSrc++ >> 8; + sum += in; + sumOfSquares += ((q63_t) (in) * (in)); + in = *pSrc++ >> 8; + sum += in; + sumOfSquares += ((q63_t) (in) * (in)); + in = *pSrc++ >> 8; + sum += in; + sumOfSquares += ((q63_t) (in) * (in)); + + /* Decrement the loop counter */ + blkCnt--; + } + + /* If the blockSize is not a multiple of 4, compute any remaining output samples here. + ** No loop unrolling is used. */ + blkCnt = blockSize % 0x4u; + + while(blkCnt > 0u) + { + /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */ + /* Compute Sum of squares of the input samples + * and then store the result in a temporary variable, sum. */ + in = *pSrc++ >> 8; + sum += in; + sumOfSquares += ((q63_t) (in) * (in)); + + /* Decrement the loop counter */ + blkCnt--; + } + + /* Compute Mean of squares of the input samples + * and then store the result in a temporary variable, meanOfSquares. */ + meanOfSquares = sumOfSquares / (q63_t)(blockSize - 1); + +#else + + /* Run the below code for Cortex-M0 */ + + /* Loop over blockSize number of values */ + blkCnt = blockSize; + + while(blkCnt > 0u) + { + /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */ + /* Compute Sum of squares of the input samples + * and then store the result in a temporary variable, sumOfSquares. */ + in = *pSrc++ >> 8; + sumOfSquares += ((q63_t) (in) * (in)); + + /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */ + /* Compute sum of all input values and then store the result in a temporary variable, sum. */ + sum += in; + + /* Decrement the loop counter */ + blkCnt--; + } + + /* Compute Mean of squares of the input samples + * and then store the result in a temporary variable, meanOfSquares. */ + meanOfSquares = sumOfSquares / (q63_t)(blockSize - 1); + +#endif /* #ifndef ARM_MATH_CM0_FAMILY */ + + /* Compute square of mean */ + squareOfMean = sum * sum / (q63_t)(blockSize * (blockSize - 1u)); + + /* Compute standard deviation and then store the result to the destination */ + arm_sqrt_q31((meanOfSquares - squareOfMean) >> 15, pResult); + +} + +/** + * @} end of STD group + */ |