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| author | joshua <joshua@joshuayun.com> | 2023-12-30 23:54:31 -0500 |
|---|---|---|
| committer | joshua <joshua@joshuayun.com> | 2023-12-30 23:54:31 -0500 |
| commit | 86608c6770cf08c138a2bdab5855072f64be09ef (patch) | |
| tree | 494a61b3ef37e76f9235a0d10f5c93d97290a35f /Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q31.c | |
| download | sdr-software-master.tar.gz | |
Diffstat (limited to 'Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q31.c')
| -rw-r--r-- | Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q31.c | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q31.c b/Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q31.c new file mode 100644 index 0000000..1452a69 --- /dev/null +++ b/Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_std_q31.c @@ -0,0 +1,147 @@ +/* ----------------------------------------------------------------------
+ * Project: CMSIS DSP Library
+ * Title: arm_std_q31.c
+ * Description: Standard deviation of the elements of a Q31 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 Q31 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 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(
+ const q31_t * pSrc,
+ uint32_t blockSize,
+ q31_t * pResult)
+{
+ uint32_t blkCnt; /* Loop counter */
+ q63_t sum = 0; /* Accumulator */
+ q63_t meanOfSquares, squareOfMean; /* Square of mean and mean of square */
+ q63_t sumOfSquares = 0; /* Sum of squares */
+ q31_t in; /* Temporary variable to store input value */
+
+ 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] */
+
+ in = *pSrc++ >> 8U;
+ /* Compute sum of squares and store result in a temporary variable, sumOfSquares. */
+ sumOfSquares += ((q63_t) (in) * (in));
+ /* Compute sum and store result in a temporary variable, sum. */
+ sum += in;
+
+ in = *pSrc++ >> 8U;
+ sumOfSquares += ((q63_t) (in) * (in));
+ sum += in;
+
+ in = *pSrc++ >> 8U;
+ sumOfSquares += ((q63_t) (in) * (in));
+ sum += in;
+
+ in = *pSrc++ >> 8U;
+ sumOfSquares += ((q63_t) (in) * (in));
+ sum += in;
+
+ /* 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++ >> 8U;
+ /* Compute sum of squares and store result in a temporary variable, sumOfSquares. */
+ sumOfSquares += ((q63_t) (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 = (sumOfSquares / (q63_t)(blockSize - 1U));
+
+ /* Compute square of mean */
+ squareOfMean = ( sum * sum / (q63_t)(blockSize * (blockSize - 1U)));
+
+ /* Compute standard deviation and store result in destination */
+ arm_sqrt_q31((meanOfSquares - squareOfMean) >> 15U, pResult);
+}
+
+/**
+ @} end of STD group
+ */
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