|
|
/* ----------------------------------------------------------------------
|
|
|
* Copyright (C) 2010 ARM Limited. All rights reserved.
|
|
|
*
|
|
|
* $Date: 15. July 2011
|
|
|
* $Revision: V1.0.10
|
|
|
*
|
|
|
* Project: CMSIS DSP Library
|
|
|
* Title: arm_sqrt_q15.c
|
|
|
*
|
|
|
* Description: Q15 square root function.
|
|
|
*
|
|
|
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
|
|
|
*
|
|
|
* Version 1.0.10 2011/7/15
|
|
|
* Big Endian support added and Merged M0 and M3/M4 Source code.
|
|
|
*
|
|
|
* Version 1.0.3 2010/11/29
|
|
|
* Re-organized the CMSIS folders and updated documentation.
|
|
|
*
|
|
|
* Version 1.0.2 2010/11/11
|
|
|
* Documentation updated.
|
|
|
*
|
|
|
* Version 1.0.1 2010/10/05
|
|
|
* Production release and review comments incorporated.
|
|
|
*
|
|
|
* Version 1.0.0 2010/09/20
|
|
|
* Production release and review comments incorporated.
|
|
|
* -------------------------------------------------------------------- */
|
|
|
|
|
|
#include "arm_math.h"
|
|
|
#include "arm_common_tables.h"
|
|
|
|
|
|
|
|
|
/**
|
|
|
* @ingroup groupFastMath
|
|
|
*/
|
|
|
|
|
|
/**
|
|
|
* @addtogroup SQRT
|
|
|
* @{
|
|
|
*/
|
|
|
|
|
|
/**
|
|
|
* @brief Q15 square root function.
|
|
|
* @param[in] in input value. The range of the input value is [0 +1) or 0x0000 to 0x7FFF.
|
|
|
* @param[out] *pOut square root of input value.
|
|
|
* @return The function returns ARM_MATH_SUCCESS if input value is positive value or ARM_MATH_ARGUMENT_ERROR if
|
|
|
* <code>in</code> is negative value and returns zero output for negative values.
|
|
|
*/
|
|
|
|
|
|
arm_status arm_sqrt_q15(
|
|
|
q15_t in,
|
|
|
q15_t * pOut)
|
|
|
{
|
|
|
q31_t prevOut;
|
|
|
q15_t oneByOut;
|
|
|
uint32_t sign_bits;
|
|
|
|
|
|
#ifndef ARM_MATH_CM0
|
|
|
|
|
|
/* Run the below code for Cortex-M4 and Cortex-M3 */
|
|
|
|
|
|
q31_t out;
|
|
|
|
|
|
if(in > 0)
|
|
|
{
|
|
|
/* run for ten iterations */
|
|
|
|
|
|
/* Take initial guess as half of the input and first iteration */
|
|
|
out = ((q31_t) in >> 1u) + 0x3FFF;
|
|
|
|
|
|
/* Calculation of reciprocal of out */
|
|
|
/* oneByOut contains reciprocal of out which is in 2.14 format
|
|
|
and oneByOut should be upscaled by signBits */
|
|
|
sign_bits = arm_recip_q15((q15_t) out, &oneByOut, armRecipTableQ15);
|
|
|
|
|
|
/* 0.5 * (out) */
|
|
|
out = out >> 1u;
|
|
|
/* prevOut = 0.5 * out + (in * (oneByOut << signBits))) */
|
|
|
prevOut = out + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
|
|
|
/* Third iteration */
|
|
|
sign_bits = arm_recip_q15((q15_t) prevOut, &oneByOut, armRecipTableQ15);
|
|
|
prevOut = prevOut >> 1u;
|
|
|
out = prevOut + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
|
|
|
sign_bits = arm_recip_q15((q15_t) out, &oneByOut, armRecipTableQ15);
|
|
|
out = out >> 1u;
|
|
|
prevOut = out + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
|
|
|
/* Fifth iteration */
|
|
|
sign_bits = arm_recip_q15((q15_t) prevOut, &oneByOut, armRecipTableQ15);
|
|
|
prevOut = prevOut >> 1u;
|
|
|
out = prevOut + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
|
|
|
sign_bits = arm_recip_q15((q15_t) out, &oneByOut, armRecipTableQ15);
|
|
|
out = out >> 1u;
|
|
|
prevOut = out + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
|
|
|
/* Seventh iteration */
|
|
|
sign_bits = arm_recip_q15((q15_t) prevOut, &oneByOut, armRecipTableQ15);
|
|
|
prevOut = prevOut >> 1u;
|
|
|
out = prevOut + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
|
|
|
sign_bits = arm_recip_q15((q15_t) out, &oneByOut, armRecipTableQ15);
|
|
|
out = out >> 1u;
|
|
|
prevOut = out + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
|
|
|
sign_bits = arm_recip_q15((q15_t) prevOut, &oneByOut, armRecipTableQ15);
|
|
|
prevOut = prevOut >> 1u;
|
|
|
out = prevOut + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
|
|
|
/* tenth iteration */
|
|
|
sign_bits = arm_recip_q15((q15_t) out, &oneByOut, armRecipTableQ15);
|
|
|
out = out >> 1u;
|
|
|
*pOut = out + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
|
|
|
return (ARM_MATH_SUCCESS);
|
|
|
}
|
|
|
|
|
|
#else
|
|
|
|
|
|
/* Run the below code for Cortex-M0 */
|
|
|
|
|
|
q31_t out, loopVar; /* Temporary variable for output, loop variable */
|
|
|
if(in > 0)
|
|
|
{
|
|
|
/* run for ten iterations */
|
|
|
|
|
|
/* Take initial guess as half of the input and first iteration */
|
|
|
out = ((q31_t) in >> 1u) + 0x3FFF;
|
|
|
|
|
|
/* Calculation of reciprocal of out */
|
|
|
|
|
|
/* oneByOut contains reciprocal of out which is in 2.14 format
|
|
|
and oneByOut should be upscaled by sign bits */
|
|
|
sign_bits = arm_recip_q15((q15_t) out, &oneByOut, armRecipTableQ15);
|
|
|
|
|
|
/* 0.5 * (out) */
|
|
|
out = out >> 1u;
|
|
|
/* prevOut = 0.5 * out + (in * oneByOut) << signbits))) */
|
|
|
prevOut = out + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
|
|
|
/* loop for third iteration to tenth iteration */
|
|
|
|
|
|
for (loopVar = 1; loopVar <= 8; loopVar++)
|
|
|
{
|
|
|
|
|
|
sign_bits = arm_recip_q15((q15_t) prevOut, &oneByOut, armRecipTableQ15);
|
|
|
/* 0.5 * (prevOut) */
|
|
|
prevOut = prevOut >> 1u;
|
|
|
/* prevOut = 0.5 * prevOut+ (in * oneByOut) << signbits))) */
|
|
|
out =
|
|
|
prevOut + (((q15_t) (((q31_t) in * oneByOut) >> 16)) << sign_bits);
|
|
|
/* prevOut = out */
|
|
|
prevOut = out;
|
|
|
|
|
|
}
|
|
|
/* output is moved to pOut pointer */
|
|
|
*pOut = prevOut;
|
|
|
|
|
|
return (ARM_MATH_SUCCESS);
|
|
|
}
|
|
|
|
|
|
#endif /* #ifndef ARM_MATH_CM0 */
|
|
|
|
|
|
else
|
|
|
{
|
|
|
|
|
|
*pOut = 0;
|
|
|
return (ARM_MATH_ARGUMENT_ERROR);
|
|
|
}
|
|
|
|
|
|
}
|
|
|
|
|
|
/**
|
|
|
* @} end of SQRT group
|
|
|
*/
|
|
|
|