Diff: DSP/source/StatisticsFunctions/arm_var_f32.c

Revision:

0:eedb7d567a5d

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DSP/source/StatisticsFunctions/arm_var_f32.c	Thu Apr 12 01:31:58 2018 +0000
@@ -0,0 +1,182 @@
+/* ----------------------------------------------------------------------
+ * Project:      CMSIS DSP Library
+ * Title:        arm_var_f32.c
+ * Description:  Variance of the elements of a floating-point 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
+ */
+
+/**
+ * @defgroup variance  Variance
+ *
+ * Calculates the variance of the elements in the input vector.
+ * The underlying algorithm used is the direct method sometimes referred to as the two-pass method:
+ *
+ * <pre>
+ *   Result = sum(element - meanOfElements)^2) / numElement - 1
+ *
+ *     where, meanOfElements = ( pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] ) / blockSize
+ *
+ * </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 fMean, fValue;
+    uint32_t blkCnt;            /* loop counter */
+    float32_t * pInput = pSrc;
+    float32_t sum = 0.0f;
+    float32_t fSum = 0.0f;
+    #if defined(ARM_MATH_DSP)
+    float32_t in1, in2, in3, in4;
+    #endif
+
+    if (blockSize <= 1U)
+    {
+        *pResult = 0;
+        return;
+    }
+
+    #if defined(ARM_MATH_DSP)
+        /* Run the below code for Cortex-M4 and Cortex-M7 */
+
+        /*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]) */
+            in1 = *pInput++;
+            in2 = *pInput++;
+            in3 = *pInput++;
+            in4 = *pInput++;
+
+            sum += in1;
+            sum += in2;
+            sum += in3;
+            sum += in4;
+
+            /* 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 or Cortex-M3 */
+
+        /* Loop over blockSize number of values */
+        blkCnt = blockSize;
+
+    #endif
+
+    while (blkCnt > 0U)
+    {
+        /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
+        sum += *pInput++;
+
+        /* Decrement the loop counter */
+        blkCnt--;
+    }
+
+    /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize  */
+    fMean = sum / (float32_t) blockSize;
+
+    pInput = pSrc;
+
+    #if defined(ARM_MATH_DSP)
+
+        /*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)
+        {
+            fValue = *pInput++ - fMean;
+            fSum += fValue * fValue;
+            fValue = *pInput++ - fMean;
+            fSum += fValue * fValue;
+            fValue = *pInput++ - fMean;
+            fSum += fValue * fValue;
+            fValue = *pInput++ - fMean;
+            fSum += fValue * fValue;
+
+            /* Decrement the loop counter */
+            blkCnt--;
+        }
+
+        blkCnt = blockSize % 0x4U;
+    #else
+        /* Run the below code for Cortex-M0 or Cortex-M3 */
+
+        /* Loop over blockSize number of values */
+        blkCnt = blockSize;
+    #endif
+
+    while (blkCnt > 0U)
+    {
+        fValue = *pInput++ - fMean;
+        fSum += fValue * fValue;
+
+        /* Decrement the loop counter */
+        blkCnt--;
+    }
+
+    /* Variance */
+    *pResult = fSum / (float32_t)(blockSize - 1.0f);
+}
+
+/**
+ * @} end of variance group
+ */
+