/* ---------------------------------------------------------------------- * Project: CMSIS DSP Library * Title: arm_var_f64.c * Description: Variance of the elements of a floating-point vector * * $Date: 13 September 2021 * $Revision: V1.10.0 * * Target Processor: Cortex-M and Cortex-A cores * -------------------------------------------------------------------- */ /* * Copyright (C) 2010-2021 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 "dsp/statistics_functions.h" /** @ingroup groupStats */ /** @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 */ ARM_DSP_ATTRIBUTE void arm_var_f64( const float64_t * pSrc, uint32_t blockSize, float64_t * pResult) { uint32_t blkCnt; /* Loop counter */ float64_t fSum = 0.; float64_t fMean, fValue; const float64_t * pInput = pSrc; if (blockSize <= 1U) { *pResult = 0; return; } arm_mean_f64(pInput, blockSize, &fMean); #if defined(ARM_MATH_NEON) && defined(__aarch64__) float64x2_t fValueV ,fsumV , pInputV , fMeanV; fsumV = vdupq_n_f64(0.0); fMeanV = vdupq_n_f64(fMean); blkCnt = blockSize >> 1U; while(blkCnt > 0U) { pInputV = vld1q_f64(pInput); fValueV = vsubq_f64(pInputV, fMeanV); fsumV = vmlaq_f64(fsumV, fValueV, fValueV); pInput += 2 ; blkCnt--; } fSum = vaddvq_f64(fsumV); blkCnt = blockSize & 1 ; #else /* Initialize blkCnt with number of samples */ blkCnt = blockSize; #endif while (blkCnt > 0U) { fValue = *pInput++ - fMean; fSum += fValue * fValue; /* Decrement loop counter */ blkCnt--; } /* Variance */ *pResult = fSum / (float64_t)(blockSize - 1.); } /** @} end of variance group */