Diff: StatisticsFunctions/arm_rms_q15.c

Revision:

0:3d9c67d97d6f

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/StatisticsFunctions/arm_rms_q15.c	Mon Jul 28 15:03:15 2014 +0000
@@ -0,0 +1,153 @@
+/* ----------------------------------------------------------------------    
+* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
+*    
+* $Date:        12. March 2014
+* $Revision: 	V1.4.3  
+*    
+* Project: 	    CMSIS DSP Library    
+* Title:		arm_rms_q15.c    
+*    
+* Description:	Root Mean Square of the elements of a Q15 vector.  
+*    
+* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
+*  
+* Redistribution and use in source and binary forms, with or without 
+* modification, are permitted provided that the following conditions
+* are met:
+*   - Redistributions of source code must retain the above copyright
+*     notice, this list of conditions and the following disclaimer.
+*   - Redistributions in binary form must reproduce the above copyright
+*     notice, this list of conditions and the following disclaimer in
+*     the documentation and/or other materials provided with the 
+*     distribution.
+*   - Neither the name of ARM LIMITED nor the names of its contributors
+*     may be used to endorse or promote products derived from this
+*     software without specific prior written permission.
+*
+* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
+* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+* POSSIBILITY OF SUCH DAMAGE.    
+* ---------------------------------------------------------------------------- */
+
+#include "arm_math.h"
+
+/**    
+ * @addtogroup RMS    
+ * @{    
+ */
+
+/**    
+ * @brief Root Mean Square of the elements of a Q15 vector.    
+ * @param[in]       *pSrc points to the input vector    
+ * @param[in]       blockSize length of the input vector    
+ * @param[out]      *pResult rms value returned here    
+ * @return none.    
+ *    
+ * @details    
+ * <b>Scaling and Overflow Behavior:</b>    
+ *    
+ * \par    
+ * The function is implemented using a 64-bit internal accumulator.    
+ * The input is represented in 1.15 format.    
+ * Intermediate multiplication yields a 2.30 format, and this    
+ * result is added without saturation to a 64-bit accumulator in 34.30 format.    
+ * With 33 guard bits in the accumulator, there is no risk of overflow, and the    
+ * full precision of the intermediate multiplication is preserved.    
+ * Finally, the 34.30 result is truncated to 34.15 format by discarding the lower     
+ * 15 bits, and then saturated to yield a result in 1.15 format.    
+ *    
+ */
+
+void arm_rms_q15(
+  q15_t * pSrc,
+  uint32_t blockSize,
+  q15_t * pResult)
+{
+  q63_t sum = 0;                                 /* accumulator */
+
+#ifndef ARM_MATH_CM0_FAMILY
+
+  /* Run the below code for Cortex-M4 and Cortex-M3 */
+
+  q31_t in;                                      /* temporary variable to store the input value */
+  q15_t in1;                                     /* temporary variable to store the input value */
+  uint32_t blkCnt;                               /* loop counter */
+
+  /* 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 the squares and then store the results in a temporary variable, sum */
+    in = *__SIMD32(pSrc)++;
+    sum = __SMLALD(in, in, sum);
+    in = *__SIMD32(pSrc)++;
+    sum = __SMLALD(in, in, sum);
+
+    /* 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 the squares and then store the results in a temporary variable, sum */
+    in1 = *pSrc++;
+    sum = __SMLALD(in1, in1, sum);
+
+    /* Decrement the loop counter */
+    blkCnt--;
+  }
+
+  /* Truncating and saturating the accumulator to 1.15 format */
+  /* Store the result in the destination */
+  arm_sqrt_q15(__SSAT((sum / (q63_t)blockSize) >> 15, 16), pResult);
+
+#else
+
+  /* Run the below code for Cortex-M0 */
+
+  q15_t in;                                      /* temporary variable to store the input value */
+  uint32_t blkCnt;                               /* loop counter */
+
+  /* Loop over blockSize number of values */
+  blkCnt = blockSize;
+
+  while(blkCnt > 0u)
+  {
+    /* C = (A[0] * A[0] + A[1] * A[1] + ... + A[blockSize-1] * A[blockSize-1]) */
+    /* Compute sum of the squares and then store the results in a temporary variable, sum */
+    in = *pSrc++;
+    sum += ((q31_t) in * in);
+
+    /* Decrement the loop counter */
+    blkCnt--;
+  }
+
+  /* Truncating and saturating the accumulator to 1.15 format */
+  /* Store the result in the destination */
+  arm_sqrt_q15(__SSAT((sum / (q63_t)blockSize) >> 15, 16), pResult);
+
+#endif /* #ifndef ARM_MATH_CM0_FAMILY */
+
+}
+
+/**    
+ * @} end of RMS group    
+ */