Diff: DSP/source/StatisticsFunctions/arm_mean_q15.c

Revision:

0:eedb7d567a5d

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DSP/source/StatisticsFunctions/arm_mean_q15.c	Thu Apr 12 01:31:58 2018 +0000
@@ -0,0 +1,121 @@
+/* ----------------------------------------------------------------------
+ * Project:      CMSIS DSP Library
+ * Title:        arm_mean_q15.c
+ * Description:  Mean value of a Q15 vector
+ *
+ * $Date:        27. January 2017
+ * $Revision:    V.1.5.1
+ *
+ * Target Processor: Cortex-M cores
+ * -------------------------------------------------------------------- */
+/*
+ * Copyright (C) 2010-2017 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 groupStats
+ */
+
+/**
+ * @addtogroup mean
+ * @{
+ */
+
+
+/**
+ * @brief Mean value of a Q15 vector.
+ * @param[in]       *pSrc points to the input vector
+ * @param[in]       blockSize length of the input vector
+ * @param[out]      *pResult mean value returned here
+ * @return none.
+ *
+ * @details
+ * <b>Scaling and Overflow Behavior:</b>
+ * \par
+ * The function is implemented using a 32-bit internal accumulator.
+ * The input is represented in 1.15 format and is accumulated in a 32-bit
+ * accumulator in 17.15 format.
+ * There is no risk of internal overflow with this approach, and the
+ * full precision of intermediate result is preserved.
+ * Finally, the accumulator is saturated and truncated to yield a result of 1.15 format.
+ *
+ */
+
+void arm_mean_q15(
+  q15_t * pSrc,
+  uint32_t blockSize,
+  q15_t * pResult)
+{
+  q31_t sum = 0;                                 /* Temporary result storage */
+  uint32_t blkCnt;                               /* loop counter */
+
+#if defined (ARM_MATH_DSP)
+  /* Run the below code for Cortex-M4 and Cortex-M3 */
+
+  q31_t in;
+
+  /*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[1] + A[2] + ... + A[blockSize-1]) */
+    in = *__SIMD32(pSrc)++;
+    sum += ((in << 16U) >> 16U);
+    sum +=  (in >> 16U);
+    in = *__SIMD32(pSrc)++;
+    sum += ((in << 16U) >> 16U);
+    sum +=  (in >> 16U);
+
+    /* 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;
+
+#else
+  /* Run the below code for Cortex-M0 */
+
+  /* Loop over blockSize number of values */
+  blkCnt = blockSize;
+
+#endif /* #if defined (ARM_MATH_DSP) */
+
+  while (blkCnt > 0U)
+  {
+    /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
+    sum += *pSrc++;
+
+    /* Decrement the loop counter */
+    blkCnt--;
+  }
+
+  /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize  */
+  /* Store the result to the destination */
+  *pResult = (q15_t) (sum / (q31_t)blockSize);
+}
+
+/**
+ * @} end of mean group
+ */
+