pigweed / third_party / github / STMicroelectronics / cmsis_core / refs/heads/cm4 / . / DSP / Source / FilteringFunctions / arm_fir_sparse_f32.c

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

* Project: CMSIS DSP Library | |

* Title: arm_fir_sparse_f32.c | |

* Description: Floating-point sparse FIR filter processing function | |

* | |

* $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 groupFilters | |

*/ | |

/** | |

@defgroup FIR_Sparse Finite Impulse Response (FIR) Sparse Filters | |

This group of functions implements sparse FIR filters. | |

Sparse FIR filters are equivalent to standard FIR filters except that most of the coefficients are equal to zero. | |

Sparse filters are used for simulating reflections in communications and audio applications. | |

There are separate functions for Q7, Q15, Q31, and floating-point data types. | |

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

<code>blockSize</code> samples through the filter. <code>pSrc</code> and | |

<code>pDst</code> points to input and output arrays respectively containing <code>blockSize</code> values. | |

@par Algorithm | |

The sparse filter instant structure contains an array of tap indices <code>pTapDelay</code> which specifies the locations of the non-zero coefficients. | |

This is in addition to the coefficient array <code>b</code>. | |

The implementation essentially skips the multiplications by zero and leads to an efficient realization. | |

<pre> | |

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

</pre> | |

@par | |

\image html FIRSparse.gif "Sparse FIR filter. b[n] represents the filter coefficients" | |

@par | |

<code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>; | |

<code>pTapDelay</code> points to an array of nonzero indices and is also of size <code>numTaps</code>; | |

<code>pState</code> points to a state array of size <code>maxDelay + blockSize</code>, where | |

<code>maxDelay</code> is the largest offset value that is ever used in the <code>pTapDelay</code> array. | |

Some of the processing functions also require temporary working buffers. | |

@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. | |

Coefficient and offset arrays may be shared among several instances while state variable arrays cannot be shared. | |

There are separate instance structure declarations for each of the 4 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, pTapDelay, maxDelay, stateIndex, pState. Also set all of the values in pState to zero. | |

@par | |

Use of the initialization function is optional. | |

However, if the initialization function is used, then the instance structure cannot be placed into a const data section. | |

To place an instance structure into a const data section, the instance structure must be manually initialized. | |

Set the values in the state buffer to zeros before static initialization. | |

The code below statically initializes each of the 4 different data type filter instance structures | |

<pre> | |

arm_fir_sparse_instance_f32 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; | |

arm_fir_sparse_instance_q31 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; | |

arm_fir_sparse_instance_q15 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; | |

arm_fir_sparse_instance_q7 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay}; | |

</pre> | |

@par Fixed-Point Behavior | |

Care must be taken when using the fixed-point versions of the sparse FIR filter functions. | |

In particular, the overflow and saturation behavior of the accumulator used in each function must be considered. | |

Refer to the function specific documentation below for usage guidelines. | |

*/ | |

/** | |

@addtogroup FIR_Sparse | |

@{ | |

*/ | |

/** | |

@brief Processing function for the floating-point sparse FIR filter. | |

@param[in] S points to an instance of the floating-point sparse FIR structure | |

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

@param[out] pDst points to the block of output data | |

@param[in] pScratchIn points to a temporary buffer of size blockSize | |

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

@return none | |

*/ | |

void arm_fir_sparse_f32( | |

arm_fir_sparse_instance_f32 * S, | |

const float32_t * pSrc, | |

float32_t * pDst, | |

float32_t * pScratchIn, | |

uint32_t blockSize) | |

{ | |

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

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

float32_t *px; /* Scratch buffer pointer */ | |

float32_t *py = pState; /* Temporary pointers for state buffer */ | |

float32_t *pb = pScratchIn; /* Temporary pointers for scratch buffer */ | |

float32_t *pOut; /* Destination pointer */ | |

int32_t *pTapDelay = S->pTapDelay; /* Pointer to the array containing offset of the non-zero tap values. */ | |

uint32_t delaySize = S->maxDelay + blockSize; /* state length */ | |

uint16_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ | |

int32_t readIndex; /* Read index of the state buffer */ | |

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

float32_t coeff = *pCoeffs++; /* Read the first coefficient value */ | |

/* BlockSize of Input samples are copied into the state buffer */ | |

/* StateIndex points to the starting position to write in the state buffer */ | |

arm_circularWrite_f32((int32_t *) py, delaySize, &S->stateIndex, 1, (int32_t *) pSrc, 1, blockSize); | |

/* Read Index, from where the state buffer should be read, is calculated. */ | |

readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++; | |

/* Wraparound of readIndex */ | |

if (readIndex < 0) | |

{ | |

readIndex += (int32_t) delaySize; | |

} | |

/* Working pointer for state buffer is updated */ | |

py = pState; | |

/* blockSize samples are read from the state buffer */ | |

arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1, | |

(int32_t *) pb, (int32_t *) pb, blockSize, 1, blockSize); | |

/* Working pointer for the scratch buffer of state values */ | |

px = pb; | |

/* Working pointer for scratch buffer of output values */ | |

pOut = pDst; | |

#if defined (ARM_MATH_LOOPUNROLL) | |

/* Loop unrolling: Compute 4 outputs at a time. */ | |

blkCnt = blockSize >> 2U; | |

while (blkCnt > 0U) | |

{ | |

/* Perform Multiplications and store in destination buffer */ | |

*pOut++ = *px++ * coeff; | |

*pOut++ = *px++ * coeff; | |

*pOut++ = *px++ * coeff; | |

*pOut++ = *px++ * coeff; | |

/* 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) | |

{ | |

/* Perform Multiplication and store in destination buffer */ | |

*pOut++ = *px++ * coeff; | |

/* Decrement loop counter */ | |

blkCnt--; | |

} | |

/* Load the coefficient value and | |

* increment the coefficient buffer for the next set of state values */ | |

coeff = *pCoeffs++; | |

/* Read Index, from where the state buffer should be read, is calculated. */ | |

readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++; | |

/* Wraparound of readIndex */ | |

if (readIndex < 0) | |

{ | |

readIndex += (int32_t) delaySize; | |

} | |

/* Loop over the number of taps. */ | |

tapCnt = (uint32_t) numTaps - 2U; | |

while (tapCnt > 0U) | |

{ | |

/* Working pointer for state buffer is updated */ | |

py = pState; | |

/* blockSize samples are read from the state buffer */ | |

arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1, | |

(int32_t *) pb, (int32_t *) pb, blockSize, 1, blockSize); | |

/* Working pointer for the scratch buffer of state values */ | |

px = pb; | |

/* Working pointer for scratch buffer of output values */ | |

pOut = pDst; | |

#if defined (ARM_MATH_LOOPUNROLL) | |

/* Loop unrolling: Compute 4 outputs at a time. */ | |

blkCnt = blockSize >> 2U; | |

while (blkCnt > 0U) | |

{ | |

/* Perform Multiply-Accumulate */ | |

*pOut++ += *px++ * coeff; | |

*pOut++ += *px++ * coeff; | |

*pOut++ += *px++ * coeff; | |

*pOut++ += *px++ * coeff; | |

/* 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) | |

{ | |

/* Perform Multiply-Accumulate */ | |

*pOut++ += *px++ * coeff; | |

/* Decrement loop counter */ | |

blkCnt--; | |

} | |

/* Load the coefficient value and | |

* increment the coefficient buffer for the next set of state values */ | |

coeff = *pCoeffs++; | |

/* Read Index, from where the state buffer should be read, is calculated. */ | |

readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++; | |

/* Wraparound of readIndex */ | |

if (readIndex < 0) | |

{ | |

readIndex += (int32_t) delaySize; | |

} | |

/* Decrement tap loop counter */ | |

tapCnt--; | |

} | |

/* Compute last tap without the final read of pTapDelay */ | |

/* Working pointer for state buffer is updated */ | |

py = pState; | |

/* blockSize samples are read from the state buffer */ | |

arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1, | |

(int32_t *) pb, (int32_t *) pb, blockSize, 1, blockSize); | |

/* Working pointer for the scratch buffer of state values */ | |

px = pb; | |

/* Working pointer for scratch buffer of output values */ | |

pOut = pDst; | |

#if defined (ARM_MATH_LOOPUNROLL) | |

/* Loop unrolling: Compute 4 outputs at a time. */ | |

blkCnt = blockSize >> 2U; | |

while (blkCnt > 0U) | |

{ | |

/* Perform Multiply-Accumulate */ | |

*pOut++ += *px++ * coeff; | |

*pOut++ += *px++ * coeff; | |

*pOut++ += *px++ * coeff; | |

*pOut++ += *px++ * coeff; | |

/* 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) | |

{ | |

/* Perform Multiply-Accumulate */ | |

*pOut++ += *px++ * coeff; | |

/* Decrement loop counter */ | |

blkCnt--; | |

} | |

} | |

/** | |

@} end of FIR_Sparse group | |

*/ |