| /* ---------------------------------------------------------------------- |
| * Copyright (C) 2010 ARM Limited. All rights reserved. |
| * |
| * $Date: 15. July 2011 |
| * $Revision: V1.0.10 |
| * |
| * Project: CMSIS DSP Library |
| * Title: arm_std_f32.c |
| * |
| * Description: Standard deviation of the elements of a floating-point vector. |
| * |
| * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 |
| * |
| * 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 |
| */ |
| |
| /** |
| * @defgroup STD Standard deviation |
| * |
| * Calculates the standard deviation of the elements in the input vector. |
| * The underlying algorithm is used: |
| * |
| * <pre> |
| * Result = sqrt((sumOfSquares - sum<sup>2</sup> / blockSize) / (blockSize - 1)) |
| * |
| * where, sumOfSquares = pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] * pSrc[blockSize-1] |
| * |
| * sum = pSrc[0] + pSrc[1] + pSrc[2] + ... + pSrc[blockSize-1] |
| * </pre> |
| * |
| * There are separate functions for floating point, Q31, and Q15 data types. |
| */ |
| |
| /** |
| * @addtogroup STD |
| * @{ |
| */ |
| |
| |
| /** |
| * @brief Standard deviation of the elements of a floating-point 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. |
| * |
| */ |
| |
| |
| void arm_std_f32( |
| float32_t * pSrc, |
| uint32_t blockSize, |
| float32_t * pResult) |
| { |
| float32_t sum = 0.0f; /* Temporary result storage */ |
| |
| #ifndef ARM_MATH_CM0 |
| |
| /* Run the below code for Cortex-M4 and Cortex-M3 */ |
| |
| float32_t meanOfSquares, mean, in, squareOfMean; |
| uint32_t blkCnt; /* loop counter */ |
| float32_t *pIn; /* Temporary pointer */ |
| |
| pIn = pSrc; |
| |
| |
| /*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 * in; |
| in = *pSrc++; |
| sum += in * in; |
| in = *pSrc++; |
| sum += in * in; |
| in = *pSrc++; |
| sum += 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 * 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 = sum / ((float32_t) blockSize - 1.0f); |
| |
| /* Reset the accumulator */ |
| sum = 0.0f; |
| |
| /*loop Unrolling */ |
| blkCnt = blockSize >> 2u; |
| |
| /* Reset the input working pointer */ |
| pSrc = pIn; |
| |
| /* 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[1] + A[2] + ... + A[blockSize-1]) */ |
| /* Compute sum of all input values and then store the result in a temporary variable, sum. */ |
| sum += *pSrc++; |
| sum += *pSrc++; |
| sum += *pSrc++; |
| sum += *pSrc++; |
| |
| /* 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[1] + A[2] + ... + A[blockSize-1]) */ |
| /* Compute sum of all input values and then store the result in a temporary variable, sum. */ |
| sum += *pSrc++; |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| /* Compute mean of all input values */ |
| mean = sum / (float32_t) blockSize; |
| |
| /* Compute square of mean */ |
| squareOfMean = (mean * mean) * (((float32_t) blockSize) / |
| ((float32_t) blockSize - 1.0f)); |
| |
| /* Compute standard deviation and then store the result to the destination */ |
| arm_sqrt_f32((meanOfSquares - squareOfMean), pResult); |
| |
| #else |
| |
| /* Run the below code for Cortex-M0 */ |
| |
| float32_t sumOfSquares = 0.0f; /* Sum of squares */ |
| float32_t squareOfSum; /* Square of Sum */ |
| float32_t in; /* input value */ |
| float32_t var; /* Temporary varaince storage */ |
| uint32_t blkCnt; /* loop counter */ |
| |
| /* 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 += in * in; |
| |
| /* C = (A[0] + A[1] + ... + A[blockSize-1]) */ |
| /* Compute Sum of the input samples |
| * and then store the result in a temporary variable, sum. */ |
| sum += in; |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| /* Compute the square of sum */ |
| squareOfSum = ((sum * sum) / (float32_t) blockSize); |
| |
| /* Compute the variance */ |
| var = ((sumOfSquares - squareOfSum) / (float32_t) (blockSize - 1.0f)); |
| |
| /* Compute standard deviation and then store the result to the destination */ |
| arm_sqrt_f32(var, pResult); |
| |
| #endif /* #ifndef ARM_MATH_CM0 */ |
| |
| } |
| |
| /** |
| * @} end of STD group |
| */ |