| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_var_f32.c |
| * Description: Variance of the elements of a floating-point 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 |
| */ |
| |
| /** |
| @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 |
| |
| 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 number of samples in input vector |
| @param[out] pResult variance value returned here |
| @return none |
| */ |
| #if defined(ARM_MATH_NEON_EXPERIMENTAL) |
| void arm_var_f32( |
| const float32_t * pSrc, |
| uint32_t blockSize, |
| float32_t * pResult) |
| { |
| float32_t mean; |
| |
| float32_t sum = 0.0f; /* accumulator */ |
| float32_t in; /* Temporary variable to store input value */ |
| uint32_t blkCnt; /* loop counter */ |
| |
| float32x4_t sumV = vdupq_n_f32(0.0f); /* Temporary result storage */ |
| float32x2_t sumV2; |
| float32x4_t inV; |
| float32x4_t avg; |
| |
| arm_mean_f32(pSrc,blockSize,&mean); |
| avg = vdupq_n_f32(mean); |
| |
| blkCnt = blockSize >> 2U; |
| |
| /* 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[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */ |
| /* Compute Power and then store the result in a temporary variable, sum. */ |
| inV = vld1q_f32(pSrc); |
| inV = vsubq_f32(inV, avg); |
| sumV = vmlaq_f32(sumV, inV, inV); |
| pSrc += 4; |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| sumV2 = vpadd_f32(vget_low_f32(sumV),vget_high_f32(sumV)); |
| sum = sumV2[0] + sumV2[1]; |
| |
| /* 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[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */ |
| /* compute power and then store the result in a temporary variable, sum. */ |
| in = *pSrc++; |
| in = in - mean; |
| sum += in * in; |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| /* Variance */ |
| *pResult = sum / (float32_t)(blockSize - 1.0f); |
| |
| } |
| |
| #else |
| void arm_var_f32( |
| const float32_t * pSrc, |
| uint32_t blockSize, |
| float32_t * pResult) |
| { |
| uint32_t blkCnt; /* Loop counter */ |
| float32_t sum = 0.0f; /* Temporary result storage */ |
| float32_t fSum = 0.0f; |
| float32_t fMean, fValue; |
| const float32_t * pInput = pSrc; |
| |
| 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[1] + A[2] + ... + A[blockSize-1]) */ |
| |
| sum += *pInput++; |
| sum += *pInput++; |
| sum += *pInput++; |
| sum += *pInput++; |
| |
| |
| /* 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[1] + A[2] + ... + A[blockSize-1]) */ |
| |
| sum += *pInput++; |
| |
| /* Decrement 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_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time */ |
| blkCnt = blockSize >> 2U; |
| |
| 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 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) |
| { |
| fValue = *pInput++ - fMean; |
| fSum += fValue * fValue; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Variance */ |
| *pResult = fSum / (float32_t)(blockSize - 1.0f); |
| } |
| #endif /* #if defined(ARM_MATH_NEON) */ |
| |
| /** |
| @} end of variance group |
| */ |