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Drivers/CMSIS/DSP/Source/BasicMathFunctions/arm_dot_prod_q31.c

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+/* ----------------------------------------------------------------------
+ * Project:      CMSIS DSP Library
+ * Title:        arm_dot_prod_q31.c
+ * Description:  Q31 dot product
+ *
+ * $Date:        18. March 2019
+ * $Revision:    V1.6.0
+ *
+ * Target Processor: Cortex-M cores
+ * -------------------------------------------------------------------- */
+/*
+ * Copyright (C) 2010-2019 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 groupMath
+ */
+
+/**
+  @addtogroup BasicDotProd
+  @{
+ */
+
+/**
+  @brief         Dot product of Q31 vectors.
+  @param[in]     pSrcA      points to the first input vector.
+  @param[in]     pSrcB      points to the second input vector.
+  @param[in]     blockSize  number of samples in each vector.
+  @param[out]    result     output result returned here.
+  @return        none
+
+  @par           Scaling and Overflow Behavior
+                   The intermediate multiplications are in 1.31 x 1.31 = 2.62 format and these
+                   are truncated to 2.48 format by discarding the lower 14 bits.
+                   The 2.48 result is then added without saturation to a 64-bit accumulator in 16.48 format.
+                   There are 15 guard bits in the accumulator and there is no risk of overflow as long as
+                   the length of the vectors is less than 2^16 elements.
+                   The return result is in 16.48 format.
+ */
+
+void arm_dot_prod_q31(
+  const q31_t * pSrcA,
+  const q31_t * pSrcB,
+        uint32_t blockSize,
+        q63_t * result)
+{
+        uint32_t blkCnt;                               /* Loop counter */
+        q63_t sum = 0;                                 /* Temporary return variable */
+
+#if defined (ARM_MATH_LOOPUNROLL)
+
+  /* Loop unrolling: Compute 4 outputs at a time */
+  blkCnt = blockSize >> 2U;
+
+  while (blkCnt > 0U)
+  {
+    /* C = A[0]* B[0] + A[1]* B[1] + A[2]* B[2] + .....+ A[blockSize-1]* B[blockSize-1] */
+
+    /* Calculate dot product and store result in a temporary buffer. */
+    sum += ((q63_t) *pSrcA++ * *pSrcB++) >> 14U;
+
+    sum += ((q63_t) *pSrcA++ * *pSrcB++) >> 14U;
+
+    sum += ((q63_t) *pSrcA++ * *pSrcB++) >> 14U;
+
+    sum += ((q63_t) *pSrcA++ * *pSrcB++) >> 14U;
+
+    /* Decrement loop counter */
+    blkCnt--;
+  }
+
+  /* Loop unrolling: Compute remaining outputs */
+  blkCnt = blockSize % 0x4U;
+
+#else
+
+  /* Initialize blkCnt with number of samples */
+  blkCnt = blockSize;
+
+#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
+
+  while (blkCnt > 0U)
+  {
+    /* C = A[0]* B[0] + A[1]* B[1] + A[2]* B[2] + .....+ A[blockSize-1]* B[blockSize-1] */
+
+    /* Calculate dot product and store result in a temporary buffer. */
+    sum += ((q63_t) *pSrcA++ * *pSrcB++) >> 14U;
+
+    /* Decrement loop counter */
+    blkCnt--;
+  }
+
+  /* Store result in destination buffer in 16.48 format */
+  *result = sum;
+}
+
+/**
+  @} end of BasicDotProd group
+ */