CMSIS DSP Software Library: arm_var_q15.c Source File
Main Page
Modules
Data Structures
Files
Examples
File List
Globals
arm_var_q15.c
Go to the documentation of this file.00001 /* ----------------------------------------------------------------------
00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
00003 *
00004 * $Date: 29. November 2010
00005 * $Revision: V1.0.3
00006 *
00007 * Project: CMSIS DSP Library
00008 * Title: arm_var_q15.c
00009 *
00010 * Description: Variance of an array of Q15 type.
00011 *
00012 * Target Processor: Cortex-M4/Cortex-M3
00013 *
00014 * Version 1.0.3 2010/11/29
00015 * Re-organized the CMSIS folders and updated documentation.
00016 *
00017 * Version 1.0.2 2010/11/11
00018 * Documentation updated.
00019 *
00020 * Version 1.0.1 2010/10/05
00021 * Production release and review comments incorporated.
00022 *
00023 * Version 1.0.0 2010/09/20
00024 * Production release and review comments incorporated.
00025 * -------------------------------------------------------------------- */
00026
00027 #include "arm_math.h"
00028
00061 void arm_var_q15(
00062 q15_t * pSrc,
00063 uint32_t blockSize,
00064 q31_t * pResult)
00065 {
00066 q63_t sum = 0; /* Accumulator */
00067 q31_t meanOfSquares, squareOfMean; /* Mean of square and square of mean */
00068 q15_t mean; /* mean */
00069 q31_t in; /* Input variable */
00070 q15_t in1; /* Temporary variable */
00071 uint32_t blkCnt; /* loop counter */
00072 q15_t t; /* Temporary variable */
00073 q15_t *pIn; /* Temporary pointer */
00074
00075 pIn = pSrc;
00076
00077 /*loop Unrolling */
00078 blkCnt = blockSize >> 2u;
00079
00080 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
00081 ** a second loop below computes the remaining 1 to 3 samples. */
00082 while(blkCnt > 0u)
00083 {
00084 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
00085 /* Compute Sum of squares of the input samples
00086 * and then store the result in a temporary variable, sum. */
00087 in = *__SIMD32(pSrc)++;
00088 sum = __SMLALD(in, in, sum);
00089 in = *__SIMD32(pSrc)++;
00090 sum = __SMLALD(in, in, sum);
00091
00092 /* Decrement the loop counter */
00093 blkCnt--;
00094 }
00095
00096 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
00097 ** No loop unrolling is used. */
00098 blkCnt = blockSize % 0x4u;
00099
00100 while(blkCnt > 0u)
00101 {
00102 /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
00103 /* Compute Sum of squares of the input samples
00104 * and then store the result in a temporary variable, sum. */
00105 in1 = *pSrc++;
00106 sum = __SMLALD(in1, in1, sum);
00107
00108 /* Decrement the loop counter */
00109 blkCnt--;
00110 }
00111
00112 /* Compute Mean of squares of the input samples
00113 * and then store the result in a temporary variable, meanOfSquares. */
00114 t = (q15_t) ((1.0f / (float32_t) (blockSize - 1u)) * 16384);
00115 sum = __SSAT((sum >> 15u), 16u);
00116
00117 meanOfSquares = (q31_t) ((sum * t) >> 14u);
00118
00119 /* Reset the accumulator */
00120 sum = 0;
00121
00122 /*loop Unrolling */
00123 blkCnt = blockSize >> 2u;
00124
00125 /* Reset the input working pointer */
00126 pSrc = pIn;
00127
00128 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
00129 ** a second loop below computes the remaining 1 to 3 samples. */
00130 while(blkCnt > 0u)
00131 {
00132 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
00133 /* Compute sum of all input values and then store the result in a temporary variable, sum. */
00134 sum += *pSrc++;
00135 sum += *pSrc++;
00136 sum += *pSrc++;
00137 sum += *pSrc++;
00138
00139 /* Decrement the loop counter */
00140 blkCnt--;
00141 }
00142
00143 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
00144 ** No loop unrolling is used. */
00145 blkCnt = blockSize % 0x4u;
00146
00147 while(blkCnt > 0u)
00148 {
00149 /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
00150 /* Compute sum of all input values and then store the result in a temporary variable, sum. */
00151 sum += *pSrc++;
00152
00153 /* Decrement the loop counter */
00154 blkCnt--;
00155 }
00156
00157 /* Compute mean of all input values */
00158 t = (q15_t) ((1.0f / (float32_t) (blockSize * (blockSize - 1u))) * 32768);
00159 mean = __SSAT(sum, 16u);
00160
00161 /* Compute square of mean */
00162 squareOfMean = ((q31_t) mean * mean) >> 15;
00163 squareOfMean = (q31_t) (((q63_t) squareOfMean * t) >> 15);
00164
00165 /* Compute variance and then store the result to the destination */
00166 *pResult = (meanOfSquares - squareOfMean);
00167
00168 }
00169
All Data Structures Files Functions Variables Typedefs Enumerations Enumerator Defines
Generated on Mon Nov 29 2010 17:19:57 for CMSIS DSP Software Library by
1.7.2