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Drivers/CMSIS/DSP/Source/StatisticsFunctions/arm_var_f16.c

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+/* ----------------------------------------------------------------------
+ * Project:      CMSIS DSP Library
+ * Title:        arm_var_f16.c
+ * Description:  Variance of the elements of a floating-point vector
+ *
+ * $Date:        23 April 2021
+ * $Revision:    V1.9.0
+ *
+ * Target Processor: Cortex-M and Cortex-A cores
+ * -------------------------------------------------------------------- */
+/*
+ * Copyright (C) 2010-2021 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 "dsp/statistics_functions_f16.h"
+
+
+#if defined(ARM_FLOAT16_SUPPORTED)
+
+
+/**
+  @ingroup groupStats
+ */
+
+
+/**
+  @addtogroup variance
+  @{
+ */
+
+/**
+  @brief         Variance of the elements of a floating-point vector.
+  @param[in]     pSrc       points to the input vector
+  @param[in]     blockSize  number of samples in input vector
+  @param[out]    pResult    variance value returned here
+  @return        none
+ */
+#if defined(ARM_MATH_MVE_FLOAT16) && !defined(ARM_MATH_AUTOVECTORIZE)
+
+#include "arm_helium_utils.h"
+
+
+void arm_var_f16(
+           const float16_t * pSrc,
+                 uint32_t blockSize,
+                 float16_t * pResult)
+{
+    int32_t         blkCnt;     /* loop counters */
+    f16x8_t         vecSrc;
+    f16x8_t         sumVec = vdupq_n_f16(0.0f16);
+    float16_t       fMean;
+
+    if (blockSize <= 1U) {
+        *pResult = 0;
+        return;
+    }
+
+
+    arm_mean_f16(pSrc, blockSize, &fMean);
+
+    blkCnt = blockSize;
+    do {
+        mve_pred16_t    p = vctp16q(blkCnt);
+
+        vecSrc = vldrhq_z_f16((float16_t const *) pSrc, p);
+        /*
+         * sum lanes
+         */
+        vecSrc = vsubq_m(vuninitializedq_f16(), vecSrc, fMean, p);
+        sumVec = vfmaq_m(sumVec, vecSrc, vecSrc, p);
+
+        blkCnt -= 8;
+        pSrc += 8;
+    }
+    while (blkCnt > 0);
+    
+    /* Variance */
+    *pResult = (_Float16)vecAddAcrossF16Mve(sumVec) / (_Float16) (blockSize - 1.0f16);
+}
+#else
+
+void arm_var_f16(
+  const float16_t * pSrc,
+        uint32_t blockSize,
+        float16_t * pResult)
+{
+        uint32_t blkCnt;                               /* Loop counter */
+        _Float16 sum = 0.0f;                          /* Temporary result storage */
+        _Float16 fSum = 0.0f;
+        _Float16 fMean, fValue;
+  const float16_t * pInput = pSrc;
+
+  if (blockSize <= 1U)
+  {
+    *pResult = 0;
+    return;
+  }
+
+#if defined (ARM_MATH_LOOPUNROLL) && !defined(ARM_MATH_AUTOVECTORIZE)
+
+  /* Loop unrolling: Compute 4 outputs at a time */
+  blkCnt = blockSize >> 2U;
+
+  while (blkCnt > 0U)
+  {
+    /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) */
+
+    sum += (_Float16)*pInput++;
+    sum += (_Float16)*pInput++;
+    sum += (_Float16)*pInput++;
+    sum += (_Float16)*pInput++;
+
+
+    /* 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] + A[1] + A[2] + ... + A[blockSize-1]) */
+
+    sum += (_Float16)*pInput++;
+
+    /* Decrement loop counter */
+    blkCnt--;
+  }
+
+  /* C = (A[0] + A[1] + A[2] + ... + A[blockSize-1]) / blockSize  */
+  fMean = (_Float16)sum / (_Float16) blockSize;
+
+  pInput = pSrc;
+
+#if defined (ARM_MATH_LOOPUNROLL) && !defined(ARM_MATH_AUTOVECTORIZE)
+
+  /* Loop unrolling: Compute 4 outputs at a time */
+  blkCnt = blockSize >> 2U;
+
+  while (blkCnt > 0U)
+  {
+    fValue = (_Float16)*pInput++ - (_Float16)fMean;
+    fSum += (_Float16)fValue * (_Float16)fValue;
+
+    fValue = (_Float16)*pInput++ - (_Float16)fMean;
+    fSum += (_Float16)fValue * (_Float16)fValue;
+
+    fValue = (_Float16)*pInput++ - (_Float16)fMean;
+    fSum += (_Float16)fValue * (_Float16)fValue;
+
+    fValue = (_Float16)*pInput++ - (_Float16)fMean;
+    fSum += (_Float16)fValue * (_Float16)fValue;
+
+    /* 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)
+  {
+    fValue = (_Float16)*pInput++ - (_Float16)fMean;
+    fSum += (_Float16)fValue * (_Float16)fValue;
+
+    /* Decrement loop counter */
+    blkCnt--;
+  }
+
+  /* Variance */
+  *pResult = (_Float16)fSum / ((_Float16)blockSize - 1.0f16);
+}
+#endif /* defined(ARM_MATH_MVEF) && !defined(ARM_MATH_AUTOVECTORIZE) */
+
+/**
+  @} end of variance group
+ */
+
+#endif /* #if defined(ARM_FLOAT16_SUPPORTED) */ 
+