Diff: src/Cortex-M4-M3/StatisticsFunctions/arm_var_f32.c

Revision:

0:1014af42efd9

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Cortex-M4-M3/StatisticsFunctions/arm_var_f32.c	Thu Mar 10 15:07:50 2011 +0000
@@ -0,0 +1,173 @@
+/* ----------------------------------------------------------------------  
+* Copyright (C) 2010 ARM Limited. All rights reserved.  
+*  
+* $Date:        29. November 2010  
+* $Revision: 	V1.0.3  
+*  
+* Project: 	    CMSIS DSP Library  
+* Title:		arm_var_f32.c  
+*  
+* Description:	Variance of an array of F32 type.  
+*  
+* Target Processor: Cortex-M4/Cortex-M3
+*  
+* Version 1.0.3 2010/11/29 
+*    Re-organized the CMSIS folders and updated documentation.  
+*   
+* Version 1.0.2 2010/11/11  
+*    Documentation updated.   
+*  
+* Version 1.0.1 2010/10/05   
+*    Production release and review comments incorporated.  
+*  
+* Version 1.0.0 2010/09/20   
+*    Production release and review comments incorporated.  
+* ---------------------------------------------------------------------------- */ 
+ 
+#include "arm_math.h" 
+ 
+/**  
+ * @ingroup groupStats  
+ */ 
+ 
+/**  
+ * @defgroup variance  Variance  
+ *  
+ * Calculates the variance of the elements in the input vector.  
+ * The underlying algorithm is used:  
+ *  
+ * <pre>  
+ * 	Result = (sumOfSquares - sum<sup>2</sup> / blockSize) / (blockSize - 1) 
+ * 
+ *	   where, sumOfSquares = pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] * pSrc[blockSize-1] 
+ * 
+ *	                   sum = pSrc[0] + pSrc[1] + pSrc[2] + ... + pSrc[blockSize-1] 
+ * </pre> 
+ *  
+ * There are separate functions for floating point, Q31, and Q15 data types.  
+ */ 
+ 
+/**  
+ * @addtogroup variance  
+ * @{  
+ */ 
+ 
+ 
+/**  
+ * @brief Variance of the elements of a floating-point vector.  
+ * @param[in]       *pSrc points to the input vector  
+ * @param[in]       blockSize length of the input vector  
+ * @param[out]      *pResult variance value returned here  
+ * @return none.  
+ *  
+ */ 
+ 
+ 
+void arm_var_f32( 
+  float32_t * pSrc, 
+  uint32_t blockSize, 
+  float32_t * pResult) 
+{ 
+  float32_t sum = (float32_t) 0.0;               /* Accumulator */ 
+  float32_t meanOfSquares, mean, in, squareOfMean;      /* Temporary variables */ 
+  uint32_t blkCnt;                               /* loop counter */ 
+  float32_t *pIn;                                /* Temporary pointer */ 
+ 
+  /* updating temporary pointer */ 
+  pIn = pSrc; 
+ 
+  /*loop Unrolling */ 
+  blkCnt = blockSize >> 2u; 
+ 
+  /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
+   ** a second loop below computes the remaining 1 to 3 samples. */ 
+  while(blkCnt > 0u) 
+  { 
+    /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1])  */ 
+    /* Compute Sum of squares of the input samples  
+     * and then store the result in a temporary variable, sum. */ 
+    in = *pSrc++; 
+    sum += in * in; 
+    in = *pSrc++; 
+    sum += in * in; 
+    in = *pSrc++; 
+    sum += in * in; 
+    in = *pSrc++; 
+    sum += in * in; 
+ 
+    /* Decrement the loop counter */ 
+    blkCnt--; 
+  } 
+ 
+  /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
+   ** No loop unrolling is used. */ 
+  blkCnt = blockSize % 0x4u; 
+ 
+  while(blkCnt > 0u) 
+  { 
+    /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */ 
+    /* Compute Sum of squares of the input samples  
+     * and then store the result in a temporary variable, sum. */ 
+    in = *pSrc++; 
+    sum += in * in; 
+ 
+    /* Decrement the loop counter */ 
+    blkCnt--; 
+  } 
+ 
+  /* Compute Mean of squares of the input samples  
+   * and then store the result in a temporary variable, meanOfSquares. */ 
+  meanOfSquares = sum / ((float32_t) blockSize - 1.0f); 
+ 
+  /* Reset the accumulator */ 
+  sum = 0.0f; 
+ 
+  /*loop Unrolling */ 
+  blkCnt = blockSize >> 2u; 
+ 
+  /* Reset the input working pointer */ 
+  pSrc = pIn; 
+ 
+  /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
+   ** a second loop below computes the remaining 1 to 3 samples. */ 
+  while(blkCnt > 0u) 
+  { 
+    /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */ 
+    /* Compute sum of all input values and then store the result in a temporary variable, sum. */ 
+    sum += *pSrc++; 
+    sum += *pSrc++; 
+    sum += *pSrc++; 
+    sum += *pSrc++; 
+ 
+    /* Decrement the loop counter */ 
+    blkCnt--; 
+  } 
+ 
+  /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
+   ** No loop unrolling is used. */ 
+  blkCnt = blockSize % 0x4u; 
+ 
+  while(blkCnt > 0u) 
+  { 
+    /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */ 
+    /* Compute sum of all input values and then store the result in a temporary variable, sum. */ 
+    sum += *pSrc++; 
+ 
+    /* Decrement the loop counter */ 
+    blkCnt--; 
+  } 
+  /* Compute mean of all input values */ 
+  mean = sum / (float32_t) blockSize; 
+ 
+  /* Compute square of mean */ 
+  squareOfMean = (mean * mean) * (((float32_t) blockSize) / 
+                                  ((float32_t) blockSize - 1.0f)); 
+ 
+  /* Compute variance and then store the result to the destination */ 
+  *pResult = meanOfSquares - squareOfMean; 
+ 
+} 
+ 
+/**  
+ * @} end of variance group  
+ */