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Drivers/CMSIS/DSP/Source/FastMathFunctions/arm_atan2_f16.c

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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
+ */