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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_scale_f32.c
* Description: Multiplies a floating-point vector by a scalar
*
* $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
*/
/**
@defgroup BasicScale Vector Scale
Multiply a vector by a scalar value. For floating-point data, the algorithm used is:
<pre>
pDst[n] = pSrc[n] * scale, 0 <= n < blockSize.
</pre>
In the fixed-point Q7, Q15, and Q31 functions, <code>scale</code> is represented by
a fractional multiplication <code>scaleFract</code> and an arithmetic shift <code>shift</code>.
The shift allows the gain of the scaling operation to exceed 1.0.
The algorithm used with fixed-point data is:
<pre>
pDst[n] = (pSrc[n] * scaleFract) << shift, 0 <= n < blockSize.
</pre>
The overall scale factor applied to the fixed-point data is
<pre>
scale = scaleFract * 2^shift.
</pre>
The functions support in-place computation allowing the source and destination
pointers to reference the same memory buffer.
*/
/**
@addtogroup BasicScale
@{
*/
/**
@brief Multiplies a floating-point vector by a scalar.
@param[in] pSrc points to the input vector
@param[in] scale scale factor to be applied
@param[out] pDst points to the output vector
@param[in] blockSize number of samples in each vector
@return none
*/
void arm_scale_f32(
const float32_t *pSrc,
float32_t scale,
float32_t *pDst,
uint32_t blockSize)
{
uint32_t blkCnt; /* Loop counter */
#if defined(ARM_MATH_NEON_EXPERIMENTAL)
float32x4_t vec1;
float32x4_t res;
/* Compute 4 outputs at a time */
blkCnt = blockSize >> 2U;
while (blkCnt > 0U)
{
/* C = A * scale */
/* Scale the input and then store the results in the destination buffer. */
vec1 = vld1q_f32(pSrc);
res = vmulq_f32(vec1, vdupq_n_f32(scale));
vst1q_f32(pDst, res);
/* Increment pointers */
pSrc += 4;
pDst += 4;
/* Decrement the loop counter */
blkCnt--;
}
/* Tail */
blkCnt = blockSize & 0x3;
#else
#if defined (ARM_MATH_LOOPUNROLL)
/* Loop unrolling: Compute 4 outputs at a time */
blkCnt = blockSize >> 2U;
while (blkCnt > 0U)
{
/* C = A * scale */
/* Scale input and store result in destination buffer. */
*pDst++ = (*pSrc++) * scale;
*pDst++ = (*pSrc++) * scale;
*pDst++ = (*pSrc++) * scale;
*pDst++ = (*pSrc++) * scale;
/* 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) */
#endif /* #if defined(ARM_MATH_NEON_EXPERIMENTAL) */
while (blkCnt > 0U)
{
/* C = A * scale */
/* Scale input and store result in destination buffer. */
*pDst++ = (*pSrc++) * scale;
/* Decrement loop counter */
blkCnt--;
}
}
/**
@} end of BasicScale group
*/
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