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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_atan2_f16.c
* Description: float16 Arc tangent of y/x
*
* $Date: 22 April 2022
* $Revision: V1.10.0
*
* Target Processor: Cortex-M and Cortex-A cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2022 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/fast_math_functions_f16.h"
#if defined(ARM_FLOAT16_SUPPORTED)
/*
atan for argument between in [0, 1.0]
*/
#define PIF16 3.14f16
#define PI16HALF 1.571f16
#define ATANHALFF16 0.463648f16
#define ATAN2_NB_COEFS_F16 5
static const float16_t atan2_coefs_f16[ATAN2_NB_COEFS_F16]={0.f16
,1.f16
,0.f16
,-0.367f16
,0.152f16
};
__STATIC_FORCEINLINE float16_t arm_atan_limited_f16(float16_t x)
{
float16_t res=atan2_coefs_f16[ATAN2_NB_COEFS_F16-1];
int i=1;
for(i=1;i<ATAN2_NB_COEFS_F16;i++)
{
res = (_Float16)x*(_Float16)res + (_Float16)atan2_coefs_f16[ATAN2_NB_COEFS_F16-1-i];
}
return(res);
}
__STATIC_FORCEINLINE float16_t arm_atan_f16(float16_t x)
{
int sign=0;
float16_t res=0.0f16;
if ((_Float16)x < 0.0f16)
{
sign=1;
x=-(_Float16)x;
}
if ((_Float16)x > 1.0f16)
{
x = 1.0f16 / (_Float16)x;
res = (_Float16)PI16HALF - (_Float16)arm_atan_limited_f16(x);
}
else
{
res += (_Float16)arm_atan_limited_f16(x);
}
if (sign)
{
res = -(_Float16)res;
}
return(res);
}
/**
@ingroup groupFastMath
*/
/**
@addtogroup atan2
@{
*/
/**
@brief Arc Tangent of y/x using sign of y and x to get right quadrant
@param[in] y y coordinate
@param[in] x x coordinate
@param[out] result Result
@return error status.
@par Compute the Arc tangent of y/x:
The sign of y and x are used to determine the right quadrant
and compute the right angle.
*/
arm_status arm_atan2_f16(float16_t y,float16_t x,float16_t *result)
{
if ((_Float16)x > 0.0f16)
{
*result=arm_atan_f16((_Float16)y/(_Float16)x);
return(ARM_MATH_SUCCESS);
}
if ((_Float16)x < 0.0f16)
{
if ((_Float16)y > 0.0f16)
{
*result=(_Float16)arm_atan_f16((_Float16)y/(_Float16)x) + (_Float16)PIF16;
}
else if ((_Float16)y < 0.0f16)
{
*result=(_Float16)arm_atan_f16((_Float16)y/(_Float16)x) - (_Float16)PIF16;
}
else
{
if (signbit(y))
{
*result= -(_Float16)PIF16;
}
else
{
*result= PIF16;
}
}
return(ARM_MATH_SUCCESS);
}
if ((_Float16)x == 0.0f16)
{
if ((_Float16)y > 0.0f16)
{
*result=PI16HALF;
return(ARM_MATH_SUCCESS);
}
if ((_Float16)y < 0.0f16)
{
*result=-(_Float16)PI16HALF;
return(ARM_MATH_SUCCESS);
}
}
return(ARM_MATH_NANINF);
}
#endif /* #if defined(ARM_FLOAT16_SUPPORTED) */
/**
@} end of atan2 group
*/
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