diff options
Diffstat (limited to 'Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q15.c')
| -rw-r--r-- | Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q15.c | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q15.c b/Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q15.c new file mode 100644 index 0000000..70d142d --- /dev/null +++ b/Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q15.c @@ -0,0 +1,161 @@ +/* ----------------------------------------------------------------------
+ * Project: CMSIS DSP Library
+ * Title: arm_std_q15.c
+ * Description: Standard deviation of an array of Q15 vector
+ *
+ * $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 "arm_math.h"
+
+/**
+ @ingroup groupStats
+ */
+
+/**
+ @addtogroup STD
+ @{
+ */
+
+/**
+ @brief Standard deviation of the elements of a Q15 vector.
+ @param[in] pSrc points to the input vector
+ @param[in] blockSize number of samples in input vector
+ @param[out] pResult standard deviation value returned here
+ @return none
+
+ @par Scaling and Overflow Behavior
+ The function is implemented using a 64-bit internal accumulator.
+ The input is represented in 1.15 format.
+ Intermediate multiplication yields a 2.30 format, and this
+ result is added without saturation to a 64-bit accumulator in 34.30 format.
+ With 33 guard bits in the accumulator, there is no risk of overflow, and the
+ full precision of the intermediate multiplication is preserved.
+ Finally, the 34.30 result is truncated to 34.15 format by discarding the lower
+ 15 bits, and then saturated to yield a result in 1.15 format.
+ */
+
+void arm_std_q15(
+ const q15_t * pSrc,
+ uint32_t blockSize,
+ q15_t * pResult)
+{
+ uint32_t blkCnt; /* Loop counter */
+ q31_t sum = 0; /* Accumulator */
+ q31_t meanOfSquares, squareOfMean; /* Square of mean and mean of square */
+ q63_t sumOfSquares = 0; /* Sum of squares */
+ q15_t in; /* Temporary variable to store input value */
+
+#if defined (ARM_MATH_LOOPUNROLL) && defined (ARM_MATH_DSP)
+ q31_t in32; /* Temporary variable to store input value */
+#endif
+
+ if (blockSize <= 1U)
+ {
+ *pResult = 0;
+ return;
+ }
+
+#if defined (ARM_MATH_LOOPUNROLL)
+
+ /* Loop unrolling: Compute 4 outputs at a time */
+ blkCnt = blockSize >> 2U;
+
+ while (blkCnt > 0U)
+ {
+ /* C = A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1] */
+ /* C = A[0] + A[1] + ... + A[blockSize-1] */
+
+ /* Compute sum of squares and store result in a temporary variable, sumOfSquares. */
+ /* Compute sum and store result in a temporary variable, sum. */
+#if defined (ARM_MATH_DSP)
+ in32 = read_q15x2_ia ((q15_t **) &pSrc);
+ sumOfSquares = __SMLALD(in32, in32, sumOfSquares);
+ sum += ((in32 << 16U) >> 16U);
+ sum += (in32 >> 16U);
+
+ in32 = read_q15x2_ia ((q15_t **) &pSrc);
+ sumOfSquares = __SMLALD(in32, in32, sumOfSquares);
+ sum += ((in32 << 16U) >> 16U);
+ sum += (in32 >> 16U);
+#else
+ in = *pSrc++;
+ sumOfSquares += (in * in);
+ sum += in;
+
+ in = *pSrc++;
+ sumOfSquares += (in * in);
+ sum += in;
+
+ in = *pSrc++;
+ sumOfSquares += (in * in);
+ sum += in;
+
+ in = *pSrc++;
+ sumOfSquares += (in * in);
+ sum += in;
+#endif /* #if defined (ARM_MATH_DSP) */
+
+ /* Decrement loop counter */
+ blkCnt--;
+ }
+
+ /* Loop unrolling: Compute remaining outputs */
+ blkCnt = blockSize % 0x4U;
+
+#else
+
+ /* Initialize blkCnt with number of samples */
+ blkCnt = blockSize;
+
+#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
+
+ while (blkCnt > 0U)
+ {
+ /* C = A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1] */
+ /* C = A[0] + A[1] + ... + A[blockSize-1] */
+
+ in = *pSrc++;
+ /* Compute sum of squares and store result in a temporary variable, sumOfSquares. */
+ sumOfSquares += (in * in);
+ /* Compute sum and store result in a temporary variable, sum. */
+ sum += in;
+
+ /* Decrement loop counter */
+ blkCnt--;
+ }
+
+ /* Compute Mean of squares and store result in a temporary variable, meanOfSquares. */
+ meanOfSquares = (q31_t) (sumOfSquares / (q63_t)(blockSize - 1U));
+
+ /* Compute square of mean */
+ squareOfMean = (q31_t) ((q63_t) sum * sum / (q63_t)(blockSize * (blockSize - 1U)));
+
+ /* mean of squares minus the square of mean. */
+ /* Compute standard deviation and store result in destination */
+ arm_sqrt_q15(__SSAT((meanOfSquares - squareOfMean) >> 15U, 16U), pResult);
+}
+
+/**
+ @} end of STD group
+ */
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