arm_rms_f32.c

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_rms_f32.c  
00009 *  
00010 * Description:  Root mean square value of an array of F32 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  
00029 /**  
00030  * @ingroup groupStats  
00031  */ 
00032  
00033 /**  
00034  * @defgroup RMS Root mean square (RMS)  
00035  *  
00036  *   
00037  * Calculates the Root Mean Sqaure of the elements in the input vector.  
00038  * The underlying algorithm is used:  
00039  *  
00040  * <pre>  
00041  *  Result = sqrt(((pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] * pSrc[blockSize-1]) / blockSize));  
00042  * </pre>  
00043  * 
00044  * There are separate functions for floating point, Q31, and Q15 data types.   
00045  */ 
00046  
00047 /**  
00048  * @addtogroup RMS  
00049  * @{  
00050  */ 
00051  
00052  
00053 /**  
00054  * @brief Root Mean Square of the elements of a floating-point vector.  
00055  * @param[in]       *pSrc points to the input vector  
00056  * @param[in]       blockSize length of the input vector  
00057  * @param[out]      *pResult rms value returned here  
00058  * @return none.  
00059  *  
00060  */ 
00061  
00062 void arm_rms_f32( 
00063   float32_t * pSrc, 
00064   uint32_t blockSize, 
00065   float32_t * pResult) 
00066 { 
00067   float32_t sum = 0.0f;                          /* Accumulator */ 
00068   float32_t in;                                  /* Tempoprary variable to store input value */ 
00069   uint32_t blkCnt;                               /* loop counter */ 
00070  
00071   /* loop Unrolling */ 
00072   blkCnt = blockSize >> 2u; 
00073  
00074   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
00075    ** a second loop below computes the remaining 1 to 3 samples. */ 
00076   while(blkCnt > 0u) 
00077   { 
00078     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */ 
00079     /* Compute sum of the squares and then store the result in a temporary variable, sum  */ 
00080     in = *pSrc++; 
00081     sum += in * in; 
00082     in = *pSrc++; 
00083     sum += in * in; 
00084     in = *pSrc++; 
00085     sum += in * in; 
00086     in = *pSrc++; 
00087     sum += in * in; 
00088  
00089     /* Decrement the loop counter */ 
00090     blkCnt--; 
00091   } 
00092  
00093   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
00094    ** No loop unrolling is used. */ 
00095   blkCnt = blockSize % 0x4u; 
00096  
00097   while(blkCnt > 0u) 
00098   { 
00099     /* C = A[0] * A[0] + A[1] * A[1] + A[2] * A[2] + ... + A[blockSize-1] * A[blockSize-1] */ 
00100     /* Compute sum of the squares and then store the results in a temporary variable, sum  */ 
00101     in = *pSrc++; 
00102     sum += in * in; 
00103  
00104     /* Decrement the loop counter */ 
00105     blkCnt--; 
00106   } 
00107  
00108   /* Compute Rms and store the result in the destination */ 
00109   arm_sqrt_f32(sum / (float32_t) blockSize, pResult); 
00110 } 
00111  
00112 /**  
00113  * @} end of RMS group  
00114  */