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Julien Chevalley
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CMSIS DSP_Lib example arm_variance_example for
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Cortex-M0, Cortex-M3, Cortex-M4 with FPU and Cortex-M7 with single precision FPU.
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The example is configured for uVision Simulator.
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/* ----------------------------------------------------------------------
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* Copyright (C) 2010-2012 ARM Limited. All rights reserved.
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*
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* $Date: 17. January 2013
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* $Revision: V1.4.0
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*
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* Project: CMSIS DSP Library
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* Title: arm_variance_example_f32.c
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*
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* Description: Example code demonstrating variance calculation of input sequence.
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*
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* Target Processor: Cortex-M4/Cortex-M3
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* - Neither the name of ARM LIMITED nor the names of its contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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* -------------------------------------------------------------------- */
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/**
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* @ingroup groupExamples
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*/
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/**
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* @defgroup VarianceExample Variance Example
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*
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* \par Description:
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* \par
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* Demonstrates the use of Basic Math and Support Functions to calculate the variance of an
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* input sequence with N samples. Uniformly distributed white noise is taken as input.
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*
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* \par Algorithm:
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* \par
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* The variance of a sequence is the mean of the squared deviation of the sequence from its mean.
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* \par
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* This is denoted by the following equation:
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* <pre> variance = ((x[0] - x') * (x[0] - x') + (x[1] - x') * (x[1] - x') + ... + * (x[n-1] - x') * (x[n-1] - x')) / (N-1)</pre>
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* where, <code>x[n]</code> is the input sequence, <code>N</code> is the number of input samples, and
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* <code>x'</code> is the mean value of the input sequence, <code>x[n]</code>.
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* \par
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* The mean value <code>x'</code> is defined as:
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* <pre> x' = (x[0] + x[1] + ... + x[n-1]) / N</pre>
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*
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* \par Block Diagram:
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* \par
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* \image html Variance.gif
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*
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*
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* \par Variables Description:
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* \par
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* \li \c testInput_f32 points to the input data
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* \li \c wire1, \c wir2, \c wire3 temporary buffers
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* \li \c blockSize number of samples processed at a time
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* \li \c refVarianceOut reference variance value
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*
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* \par CMSIS DSP Software Library Functions Used:
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* \par
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* - arm_dot_prod_f32()
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* - arm_mult_f32()
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* - arm_sub_f32()
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* - arm_fill_f32()
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* - arm_copy_f32()
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*
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* <b> Refer </b>
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* \link arm_variance_example_f32.c \endlink
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*
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*/
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/** \example arm_variance_example_f32.c
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*/
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#include <math.h>
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#include "arm_math.h"
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/* ----------------------------------------------------------------------
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* Defines each of the tests performed
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* ------------------------------------------------------------------- */
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#define MAX_BLOCKSIZE 32
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#define DELTA (0.000001f)
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/* ----------------------------------------------------------------------
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* Declare I/O buffers
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* ------------------------------------------------------------------- */
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float32_t wire1[MAX_BLOCKSIZE];
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float32_t wire2[MAX_BLOCKSIZE];
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float32_t wire3[MAX_BLOCKSIZE];
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/* ----------------------------------------------------------------------
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* Test input data for Floating point Variance example for 32-blockSize
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* Generated by the MATLAB randn() function
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* ------------------------------------------------------------------- */
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float32_t testInput_f32[32] =
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{
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-0.432564811528221, -1.665584378238097, 0.125332306474831, 0.287676420358549,
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-1.146471350681464, 1.190915465642999, 1.189164201652103, -0.037633276593318,
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0.327292361408654, 0.174639142820925, -0.186708577681439, 0.725790548293303,
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-0.588316543014189, 2.183185818197101, -0.136395883086596, 0.113931313520810,
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1.066768211359189, 0.059281460523605, -0.095648405483669, -0.832349463650022,
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0.294410816392640, -1.336181857937804, 0.714324551818952, 1.623562064446271,
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-0.691775701702287, 0.857996672828263, 1.254001421602532, -1.593729576447477,
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-1.440964431901020, 0.571147623658178, -0.399885577715363, 0.689997375464345
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};
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/* ----------------------------------------------------------------------
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* Declare Global variables
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* ------------------------------------------------------------------- */
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uint32_t blockSize = 32;
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float32_t refVarianceOut = 0.903941793931839;
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/* ----------------------------------------------------------------------
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* Variance calculation test
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* ------------------------------------------------------------------- */
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int32_t main(void)
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{
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arm_status status;
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float32_t mean, oneByBlockSize;
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float32_t variance;
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float32_t diff;
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status = ARM_MATH_SUCCESS;
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/* Calculation of mean value of input */
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/* x' = 1/blockSize * (x(0)* 1 + x(1) * 1 + ... + x(n-1) * 1) */
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/* Fill wire1 buffer with 1.0 value */
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arm_fill_f32(1.0, wire1, blockSize);
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/* Calculate the dot product of wire1 and wire2 */
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/* (x(0)* 1 + x(1) * 1 + ...+ x(n-1) * 1) */
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arm_dot_prod_f32(testInput_f32, wire1, blockSize, &mean);
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/* Calculation of 1/blockSize */
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oneByBlockSize = 1.0 / (blockSize);
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/* 1/blockSize * (x(0)* 1 + x(1) * 1 + ... + x(n-1) * 1) */
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arm_mult_f32(&mean, &oneByBlockSize, &mean, 1);
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/* Calculation of variance value of input */
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/* (1/blockSize) * (x(0) - x') * (x(0) - x') + (x(1) - x') * (x(1) - x') + ... + (x(n-1) - x') * (x(n-1) - x') */
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/* Fill wire2 with mean value x' */
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arm_fill_f32(mean, wire2, blockSize);
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/* wire3 contains (x-x') */
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arm_sub_f32(testInput_f32, wire2, wire3, blockSize);
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/* wire2 contains (x-x') */
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arm_copy_f32(wire3, wire2, blockSize);
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/* (x(0) - x') * (x(0) - x') + (x(1) - x') * (x(1) - x') + ... + (x(n-1) - x') * (x(n-1) - x') */
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arm_dot_prod_f32(wire2, wire3, blockSize, &variance);
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/* Calculation of 1/blockSize */
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oneByBlockSize = 1.0 / (blockSize - 1);
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/* Calculation of variance */
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arm_mult_f32(&variance, &oneByBlockSize, &variance, 1);
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/* absolute value of difference between ref and test */
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diff = fabsf(refVarianceOut - variance);
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/* Comparison of variance value with reference */
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if (diff > DELTA)
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{
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status = ARM_MATH_TEST_FAILURE;
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}
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if ( status != ARM_MATH_SUCCESS)
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{
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while (1);
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}
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while (1); /* main function does not return */
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}
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/** \endlink */
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