pigweed / third_party / github / STMicroelectronics / cmsis_core / 7dd288b23bf605a3a2fafa81a29d2c96a2fd83ce / . / DSP_Lib / Source / FilteringFunctions / arm_lms_norm_f32.c

/* ---------------------------------------------------------------------- | |

* Copyright (C) 2010-2014 ARM Limited. All rights reserved. | |

* | |

* $Date: 19. March 2015 | |

* $Revision: V.1.4.5 | |

* | |

* Project: CMSIS DSP Library | |

* Title: arm_lms_norm_f32.c | |

* | |

* Description: Processing function for the floating-point Normalised LMS. | |

* | |

* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 | |

* | |

* Redistribution and use in source and binary forms, with or without | |

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* software without specific prior written permission. | |

* | |

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* -------------------------------------------------------------------- */ | |

#include "arm_math.h" | |

/** | |

* @ingroup groupFilters | |

*/ | |

/** | |

* @defgroup LMS_NORM Normalized LMS Filters | |

* | |

* This set of functions implements a commonly used adaptive filter. | |

* It is related to the Least Mean Square (LMS) adaptive filter and includes an additional normalization | |

* factor which increases the adaptation rate of the filter. | |

* The CMSIS DSP Library contains normalized LMS filter functions that operate on Q15, Q31, and floating-point data types. | |

* | |

* A normalized least mean square (NLMS) filter consists of two components as shown below. | |

* The first component is a standard transversal or FIR filter. | |

* The second component is a coefficient update mechanism. | |

* The NLMS filter has two input signals. | |

* The "input" feeds the FIR filter while the "reference input" corresponds to the desired output of the FIR filter. | |

* That is, the FIR filter coefficients are updated so that the output of the FIR filter matches the reference input. | |

* The filter coefficient update mechanism is based on the difference between the FIR filter output and the reference input. | |

* This "error signal" tends towards zero as the filter adapts. | |

* The NLMS processing functions accept the input and reference input signals and generate the filter output and error signal. | |

* \image html LMS.gif "Internal structure of the NLMS adaptive filter" | |

* | |

* The functions operate on blocks of data and each call to the function processes | |

* <code>blockSize</code> samples through the filter. | |

* <code>pSrc</code> points to input signal, <code>pRef</code> points to reference signal, | |

* <code>pOut</code> points to output signal and <code>pErr</code> points to error signal. | |

* All arrays contain <code>blockSize</code> values. | |

* | |

* The functions operate on a block-by-block basis. | |

* Internally, the filter coefficients <code>b[n]</code> are updated on a sample-by-sample basis. | |

* The convergence of the LMS filter is slower compared to the normalized LMS algorithm. | |

* | |

* \par Algorithm: | |

* The output signal <code>y[n]</code> is computed by a standard FIR filter: | |

* <pre> | |

* y[n] = b[0] * x[n] + b[1] * x[n-1] + b[2] * x[n-2] + ...+ b[numTaps-1] * x[n-numTaps+1] | |

* </pre> | |

* | |

* \par | |

* The error signal equals the difference between the reference signal <code>d[n]</code> and the filter output: | |

* <pre> | |

* e[n] = d[n] - y[n]. | |

* </pre> | |

* | |

* \par | |

* After each sample of the error signal is computed the instanteous energy of the filter state variables is calculated: | |

* <pre> | |

* E = x[n]^2 + x[n-1]^2 + ... + x[n-numTaps+1]^2. | |

* </pre> | |

* The filter coefficients <code>b[k]</code> are then updated on a sample-by-sample basis: | |

* <pre> | |

* b[k] = b[k] + e[n] * (mu/E) * x[n-k], for k=0, 1, ..., numTaps-1 | |

* </pre> | |

* where <code>mu</code> is the step size and controls the rate of coefficient convergence. | |

*\par | |

* In the APIs, <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>. | |

* Coefficients are stored in time reversed order. | |

* \par | |

* <pre> | |

* {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]} | |

* </pre> | |

* \par | |

* <code>pState</code> points to a state array of size <code>numTaps + blockSize - 1</code>. | |

* Samples in the state buffer are stored in the order: | |

* \par | |

* <pre> | |

* {x[n-numTaps+1], x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2]....x[0], x[1], ..., x[blockSize-1]} | |

* </pre> | |

* \par | |

* Note that the length of the state buffer exceeds the length of the coefficient array by <code>blockSize-1</code> samples. | |

* The increased state buffer length allows circular addressing, which is traditionally used in FIR filters, | |

* to be avoided and yields a significant speed improvement. | |

* The state variables are updated after each block of data is processed. | |

* \par Instance Structure | |

* The coefficients and state variables for a filter are stored together in an instance data structure. | |

* A separate instance structure must be defined for each filter and | |

* coefficient and state arrays cannot be shared among instances. | |

* There are separate instance structure declarations for each of the 3 supported data types. | |

* | |

* \par Initialization Functions | |

* There is also an associated initialization function for each data type. | |

* The initialization function performs the following operations: | |

* - Sets the values of the internal structure fields. | |

* - Zeros out the values in the state buffer. | |

* To do this manually without calling the init function, assign the follow subfields of the instance structure: | |

* numTaps, pCoeffs, mu, energy, x0, pState. Also set all of the values in pState to zero. | |

* For Q7, Q15, and Q31 the following fields must also be initialized; | |

* recipTable, postShift | |

* | |

* \par | |

* Instance structure cannot be placed into a const data section and it is recommended to use the initialization function. | |

* \par Fixed-Point Behavior: | |

* Care must be taken when using the Q15 and Q31 versions of the normalised LMS filter. | |

* The following issues must be considered: | |

* - Scaling of coefficients | |

* - Overflow and saturation | |

* | |

* \par Scaling of Coefficients: | |

* Filter coefficients are represented as fractional values and | |

* coefficients are restricted to lie in the range <code>[-1 +1)</code>. | |

* The fixed-point functions have an additional scaling parameter <code>postShift</code>. | |

* At the output of the filter's accumulator is a shift register which shifts the result by <code>postShift</code> bits. | |

* This essentially scales the filter coefficients by <code>2^postShift</code> and | |

* allows the filter coefficients to exceed the range <code>[+1 -1)</code>. | |

* The value of <code>postShift</code> is set by the user based on the expected gain through the system being modeled. | |

* | |

* \par Overflow and Saturation: | |

* Overflow and saturation behavior of the fixed-point Q15 and Q31 versions are | |

* described separately as part of the function specific documentation below. | |

*/ | |

/** | |

* @addtogroup LMS_NORM | |

* @{ | |

*/ | |

/** | |

* @brief Processing function for floating-point normalized LMS filter. | |

* @param[in] *S points to an instance of the floating-point normalized LMS filter structure. | |

* @param[in] *pSrc points to the block of input data. | |

* @param[in] *pRef points to the block of reference data. | |

* @param[out] *pOut points to the block of output data. | |

* @param[out] *pErr points to the block of error data. | |

* @param[in] blockSize number of samples to process. | |

* @return none. | |

*/ | |

void arm_lms_norm_f32( | |

arm_lms_norm_instance_f32 * S, | |

float32_t * pSrc, | |

float32_t * pRef, | |

float32_t * pOut, | |

float32_t * pErr, | |

uint32_t blockSize) | |

{ | |

float32_t *pState = S->pState; /* State pointer */ | |

float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ | |

float32_t *pStateCurnt; /* Points to the current sample of the state */ | |

float32_t *px, *pb; /* Temporary pointers for state and coefficient buffers */ | |

float32_t mu = S->mu; /* Adaptive factor */ | |

uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ | |

uint32_t tapCnt, blkCnt; /* Loop counters */ | |

float32_t energy; /* Energy of the input */ | |

float32_t sum, e, d; /* accumulator, error, reference data sample */ | |

float32_t w, x0, in; /* weight factor, temporary variable to hold input sample and state */ | |

/* Initializations of error, difference, Coefficient update */ | |

e = 0.0f; | |

d = 0.0f; | |

w = 0.0f; | |

energy = S->energy; | |

x0 = S->x0; | |

/* S->pState points to buffer which contains previous frame (numTaps - 1) samples */ | |

/* pStateCurnt points to the location where the new input data should be written */ | |

pStateCurnt = &(S->pState[(numTaps - 1u)]); | |

/* Loop over blockSize number of values */ | |

blkCnt = blockSize; | |

#ifndef ARM_MATH_CM0_FAMILY | |

/* Run the below code for Cortex-M4 and Cortex-M3 */ | |

while(blkCnt > 0u) | |

{ | |

/* Copy the new input sample into the state buffer */ | |

*pStateCurnt++ = *pSrc; | |

/* Initialize pState pointer */ | |

px = pState; | |

/* Initialize coeff pointer */ | |

pb = (pCoeffs); | |

/* Read the sample from input buffer */ | |

in = *pSrc++; | |

/* Update the energy calculation */ | |

energy -= x0 * x0; | |

energy += in * in; | |

/* Set the accumulator to zero */ | |

sum = 0.0f; | |

/* Loop unrolling. Process 4 taps at a time. */ | |

tapCnt = numTaps >> 2; | |

while(tapCnt > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

sum += (*px++) * (*pb++); | |

sum += (*px++) * (*pb++); | |

sum += (*px++) * (*pb++); | |

sum += (*px++) * (*pb++); | |

/* Decrement the loop counter */ | |

tapCnt--; | |

} | |

/* If the filter length is not a multiple of 4, compute the remaining filter taps */ | |

tapCnt = numTaps % 0x4u; | |

while(tapCnt > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

sum += (*px++) * (*pb++); | |

/* Decrement the loop counter */ | |

tapCnt--; | |

} | |

/* The result in the accumulator, store in the destination buffer. */ | |

*pOut++ = sum; | |

/* Compute and store error */ | |

d = (float32_t) (*pRef++); | |

e = d - sum; | |

*pErr++ = e; | |

/* Calculation of Weighting factor for updating filter coefficients */ | |

/* epsilon value 0.000000119209289f */ | |

w = (e * mu) / (energy + 0.000000119209289f); | |

/* Initialize pState pointer */ | |

px = pState; | |

/* Initialize coeff pointer */ | |

pb = (pCoeffs); | |

/* Loop unrolling. Process 4 taps at a time. */ | |

tapCnt = numTaps >> 2; | |

/* Update filter coefficients */ | |

while(tapCnt > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

*pb += w * (*px++); | |

pb++; | |

*pb += w * (*px++); | |

pb++; | |

*pb += w * (*px++); | |

pb++; | |

*pb += w * (*px++); | |

pb++; | |

/* Decrement the loop counter */ | |

tapCnt--; | |

} | |

/* If the filter length is not a multiple of 4, compute the remaining filter taps */ | |

tapCnt = numTaps % 0x4u; | |

while(tapCnt > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

*pb += w * (*px++); | |

pb++; | |

/* Decrement the loop counter */ | |

tapCnt--; | |

} | |

x0 = *pState; | |

/* Advance state pointer by 1 for the next sample */ | |

pState = pState + 1; | |

/* Decrement the loop counter */ | |

blkCnt--; | |

} | |

S->energy = energy; | |

S->x0 = x0; | |

/* Processing is complete. Now copy the last numTaps - 1 samples to the | |

satrt of the state buffer. This prepares the state buffer for the | |

next function call. */ | |

/* Points to the start of the pState buffer */ | |

pStateCurnt = S->pState; | |

/* Loop unrolling for (numTaps - 1u)/4 samples copy */ | |

tapCnt = (numTaps - 1u) >> 2u; | |

/* copy data */ | |

while(tapCnt > 0u) | |

{ | |

*pStateCurnt++ = *pState++; | |

*pStateCurnt++ = *pState++; | |

*pStateCurnt++ = *pState++; | |

*pStateCurnt++ = *pState++; | |

/* Decrement the loop counter */ | |

tapCnt--; | |

} | |

/* Calculate remaining number of copies */ | |

tapCnt = (numTaps - 1u) % 0x4u; | |

/* Copy the remaining q31_t data */ | |

while(tapCnt > 0u) | |

{ | |

*pStateCurnt++ = *pState++; | |

/* Decrement the loop counter */ | |

tapCnt--; | |

} | |

#else | |

/* Run the below code for Cortex-M0 */ | |

while(blkCnt > 0u) | |

{ | |

/* Copy the new input sample into the state buffer */ | |

*pStateCurnt++ = *pSrc; | |

/* Initialize pState pointer */ | |

px = pState; | |

/* Initialize pCoeffs pointer */ | |

pb = pCoeffs; | |

/* Read the sample from input buffer */ | |

in = *pSrc++; | |

/* Update the energy calculation */ | |

energy -= x0 * x0; | |

energy += in * in; | |

/* Set the accumulator to zero */ | |

sum = 0.0f; | |

/* Loop over numTaps number of values */ | |

tapCnt = numTaps; | |

while(tapCnt > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

sum += (*px++) * (*pb++); | |

/* Decrement the loop counter */ | |

tapCnt--; | |

} | |

/* The result in the accumulator is stored in the destination buffer. */ | |

*pOut++ = sum; | |

/* Compute and store error */ | |

d = (float32_t) (*pRef++); | |

e = d - sum; | |

*pErr++ = e; | |

/* Calculation of Weighting factor for updating filter coefficients */ | |

/* epsilon value 0.000000119209289f */ | |

w = (e * mu) / (energy + 0.000000119209289f); | |

/* Initialize pState pointer */ | |

px = pState; | |

/* Initialize pCcoeffs pointer */ | |

pb = pCoeffs; | |

/* Loop over numTaps number of values */ | |

tapCnt = numTaps; | |

while(tapCnt > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

*pb += w * (*px++); | |

pb++; | |

/* Decrement the loop counter */ | |

tapCnt--; | |

} | |

x0 = *pState; | |

/* Advance state pointer by 1 for the next sample */ | |

pState = pState + 1; | |

/* Decrement the loop counter */ | |

blkCnt--; | |

} | |

S->energy = energy; | |

S->x0 = x0; | |

/* Processing is complete. Now copy the last numTaps - 1 samples to the | |

satrt of the state buffer. This prepares the state buffer for the | |

next function call. */ | |

/* Points to the start of the pState buffer */ | |

pStateCurnt = S->pState; | |

/* Copy (numTaps - 1u) samples */ | |

tapCnt = (numTaps - 1u); | |

/* Copy the remaining q31_t data */ | |

while(tapCnt > 0u) | |

{ | |

*pStateCurnt++ = *pState++; | |

/* Decrement the loop counter */ | |

tapCnt--; | |

} | |

#endif /* #ifndef ARM_MATH_CM0_FAMILY */ | |

} | |

/** | |

* @} end of LMS_NORM group | |

*/ |