| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_var_f32.c |
| * Description: Variance of the elements of a floating-point vector |
| * |
| * $Date: 27. January 2017 |
| * $Revision: V.1.5.1 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2017 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 |
| */ |
| |
| /** |
| * @defgroup variance Variance |
| * |
| * Calculates the variance of the elements in the input vector. |
| * The underlying algorithm used is the direct method sometimes referred to as the two-pass method: |
| * |
| * <pre> |
| * Result = sum(element - meanOfElements)^2) / numElement - 1 |
| * |
| * where, meanOfElements = ( pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] ) / blockSize |
| * |
| * </pre> |
| * |
| * There are separate functions for floating point, Q31, and Q15 data types. |
| */ |
| |
| /** |
| * @addtogroup variance |
| * @{ |
| */ |
| |
| |
| /** |
| * @brief Variance 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 variance value returned here |
| * @return none. |
| */ |
| |
| void arm_var_f32( |
| float32_t * pSrc, |
| uint32_t blockSize, |
| float32_t * pResult) |
| { |
| float32_t fMean, fValue; |
| uint32_t blkCnt; /* loop counter */ |
| float32_t * pInput = pSrc; |
| float32_t sum = 0.0f; |
| float32_t fSum = 0.0f; |
| #if defined(ARM_MATH_DSP) |
| float32_t in1, in2, in3, in4; |
| #endif |
| |
| if (blockSize <= 1U) |
| { |
| *pResult = 0; |
| return; |
| } |
| |
| #if defined(ARM_MATH_DSP) |
| /* Run the below code for Cortex-M4 and Cortex-M7 */ |
| |
| /*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[1] + A[2] + ... + A[blockSize-1]) */ |
| in1 = *pInput++; |
| in2 = *pInput++; |
| in3 = *pInput++; |
| in4 = *pInput++; |
| |
| sum += in1; |
| sum += in2; |
| sum += in3; |
| sum += in4; |
| |
| /* 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; |
| |
| #else |
| /* Run the below code for Cortex-M0 or Cortex-M3 */ |
| |
| /* Loop over blockSize number of values */ |
| blkCnt = blockSize; |
| |
| #endif |
| |
| while (blkCnt > 0U) |
| { |
| /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */ |
| sum += *pInput++; |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize */ |
| fMean = sum / (float32_t) blockSize; |
| |
| pInput = pSrc; |
| |
| #if defined(ARM_MATH_DSP) |
| |
| /*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) |
| { |
| fValue = *pInput++ - fMean; |
| fSum += fValue * fValue; |
| fValue = *pInput++ - fMean; |
| fSum += fValue * fValue; |
| fValue = *pInput++ - fMean; |
| fSum += fValue * fValue; |
| fValue = *pInput++ - fMean; |
| fSum += fValue * fValue; |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| blkCnt = blockSize % 0x4U; |
| #else |
| /* Run the below code for Cortex-M0 or Cortex-M3 */ |
| |
| /* Loop over blockSize number of values */ |
| blkCnt = blockSize; |
| #endif |
| |
| while (blkCnt > 0U) |
| { |
| fValue = *pInput++ - fMean; |
| fSum += fValue * fValue; |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| /* Variance */ |
| *pResult = fSum / (float32_t)(blockSize - 1.0f); |
| } |
| |
| /** |
| * @} end of variance group |
| */ |