51 lines
1.7 KiB
C
51 lines
1.7 KiB
C
/************************************************************************
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* lib/math/lib_libsqrtapprox.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 <stdint.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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float lib_sqrtapprox(float x)
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{
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int32_t i;
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/* Floats + bit manipulation = +inf fun! */
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i = *((int32_t *) & x);
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i = 0x1fc00000 + (i >> 1);
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x = *((float *)&i);
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return x;
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}
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