forked from Archive/PX4-Autopilot
104 lines
3.2 KiB
C
104 lines
3.2 KiB
C
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/************************************************************************
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* libc/math/lib_libexpi.c
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*
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* This file is a part of NuttX:
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*
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* Copyright (C) 2012 Gregory Nutt. All rights reserved.
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* Ported by: Darcy Gong
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*
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* It derives from the Rhombs OS math library by Nick Johnson which has
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* a compatibile, MIT-style license:
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*
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* Copyright (C) 2009-2011 Nick Johnson <nickbjohnson4224 at gmail.com>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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************************************************************************/
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/************************************************************************
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* Included Files
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************************************************************************/
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#include <nuttx/config.h>
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#include <nuttx/compiler.h>
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#include <sys/types.h>
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#include <math.h>
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/************************************************************************
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* Public Functions
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************************************************************************/
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/************************************************************************
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* Pre-processor Definitions
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************************************************************************/
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#define M_E2 (M_E * M_E)
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#define M_E4 (M_E2 * M_E2)
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#define M_E8 (M_E4 * M_E4)
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#define M_E16 (M_E8 * M_E8)
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#define M_E32 (M_E16 * M_E16)
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#define M_E64 (M_E32 * M_E32)
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#define M_E128 (M_E64 * M_E64)
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#define M_E256 (M_E128 * M_E128)
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#define M_E512 (M_E256 * M_E256)
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#define M_E1024 (M_E512 * M_E512)
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/************************************************************************
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* Private Data
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************************************************************************/
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static double _expi_square_tbl[11] =
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{
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M_E, // e^1
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M_E2, // e^2
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M_E4, // e^4
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M_E8, // e^8
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M_E16, // e^16
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M_E32, // e^32
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M_E64, // e^64
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M_E128, // e^128
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M_E256, // e^256
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M_E512, // e^512
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M_E1024, // e^1024
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};
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/************************************************************************
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* Public Functions
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************************************************************************/
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double lib_expi(size_t n)
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{
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size_t i;
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double val;
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if (n > 1024)
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{
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return INFINITY;
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}
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val = 1.0;
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for (i = 0; n; i++)
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{
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if (n & (1 << i))
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{
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n &= ~(1 << i);
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val *= _expi_square_tbl[i];
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}
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}
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return val;
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}
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