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Diffstat (limited to 'src/modules/mathlib/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c')
| -rw-r--r-- | src/modules/mathlib/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/src/modules/mathlib/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c b/src/modules/mathlib/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c new file mode 100644 index 000000000..45bec01a1 --- /dev/null +++ b/src/modules/mathlib/CMSIS/DSP_Lib/Source/StatisticsFunctions/arm_std_q31.c @@ -0,0 +1,184 @@ +/* ----------------------------------------------------------------------
+* Copyright (C) 2010 ARM Limited. All rights reserved.
+*
+* $Date: 15. February 2012
+* $Revision: V1.1.0
+*
+* 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
+*
+* Version 1.1.0 2012/02/15
+* Updated with more optimizations, bug fixes and minor API changes.
+*
+* Version 1.0.10 2011/7/15
+* Big Endian support added and Merged M0 and M3/M4 Source code.
+*
+* Version 1.0.3 2010/11/29
+* Re-organized the CMSIS folders and updated documentation.
+*
+* Version 1.0.2 2010/11/11
+* Documentation updated.
+*
+* Version 1.0.1 2010/10/05
+* Production release and review comments incorporated.
+*
+* Version 1.0.0 2010/09/20
+* Production release and review comments incorporated.
+* -------------------------------------------------------------------- */
+
+#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, and intermediate multiplication
+ * yields a 2.62 format.
+ * The accumulator maintains full precision of the intermediate multiplication results,
+ * but provides only a single guard bit.
+ * 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) bits, as a total of blockSize additions are performed internally.
+ * Finally, the 2.62 accumulator is right shifted by 31 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 */
+ q31_t meanOfSquares, squareOfMean; /* square of mean and mean of square */
+ q31_t mean; /* mean */
+ q31_t in; /* input value */
+ q31_t t; /* Temporary variable */
+ uint32_t blkCnt; /* loop counter */
+ q63_t sumOfSquares = 0; /* Accumulator */
+
+#ifndef ARM_MATH_CM0
+
+ /* 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++;
+ sum += in;
+ sumOfSquares += ((q63_t) (in) * (in));
+ in = *pSrc++;
+ sum += in;
+ sumOfSquares += ((q63_t) (in) * (in));
+ in = *pSrc++;
+ sum += in;
+ sumOfSquares += ((q63_t) (in) * (in));
+ in = *pSrc++;
+ 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++;
+ sum += in;
+ sumOfSquares += ((q63_t) (in) * (in));
+
+ /* Decrement the loop counter */
+ blkCnt--;
+ }
+
+ t = (q31_t) ((1.0f / (float32_t) (blockSize - 1u)) * 1073741824.0f);
+
+ /* Compute Mean of squares of the input samples
+ * and then store the result in a temporary variable, meanOfSquares. */
+ sumOfSquares = (sumOfSquares >> 31);
+ meanOfSquares = (q31_t) ((sumOfSquares * t) >> 30);
+
+#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++;
+ 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. */
+ t = (q31_t) ((1.0f / (float32_t) (blockSize - 1u)) * 1073741824.0f);
+ sumOfSquares = (sumOfSquares >> 31);
+ meanOfSquares = (q31_t) ((sumOfSquares * t) >> 30);
+
+#endif /* #ifndef ARM_MATH_CM0 */
+
+ /* Compute mean of all input values */
+ t = (q31_t) ((1.0f / (blockSize * (blockSize - 1u))) * 2147483648.0f);
+ mean = (q31_t) (sum);
+
+ /* Compute square of mean */
+ squareOfMean = (q31_t) (((q63_t) mean * mean) >> 31);
+ squareOfMean = (q31_t) (((q63_t) squareOfMean * t) >> 31);
+
+
+ /* Compute standard deviation and then store the result to the destination */
+ arm_sqrt_q31(meanOfSquares - squareOfMean, pResult);
+
+}
+
+/**
+ * @} end of STD group
+ */
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