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Diffstat (limited to 'nuttx/libc/math/lib_sqrtf.c')
-rw-r--r-- | nuttx/libc/math/lib_sqrtf.c | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/nuttx/libc/math/lib_sqrtf.c b/nuttx/libc/math/lib_sqrtf.c new file mode 100644 index 000000000..cf45ccacc --- /dev/null +++ b/nuttx/libc/math/lib_sqrtf.c @@ -0,0 +1,84 @@ +/************************************************************************ + * libc/math/lib_sqrtf.c + * + * This file is a part of NuttX: + * + * Copyright (C) 2012 Gregory Nutt. All rights reserved. + * Ported by: Darcy Gong + * + * It derives from the Rhombs OS math library by Nick Johnson which has + * a compatibile, MIT-style license: + * + * Copyright (C) 2009-2011 Nick Johnson <nickbjohnson4224 at gmail.com> + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + * + ************************************************************************/ + +/************************************************************************ + * Included Files + ************************************************************************/ + +#include <nuttx/config.h> +#include <nuttx/compiler.h> + +#include <math.h> +#include <errno.h> + +#include "lib_internal.h" + +/************************************************************************ + * Public Functions + ************************************************************************/ + +float sqrtf(float x) +{ + float y; + + /* Filter out invalid/trivial inputs */ + + if (x < 0.0) + { + errno = EDOM; + return NAN; + } + + if (isnan(x)) + { + return NAN; + } + + if (isinf(x)) + { + return INFINITY; + } + + if (x == 0.0) + { + return 0.0; + } + + /* Guess square root (using bit manipulation) */ + + y = lib_sqrtapprox(x); + + /* Perform three iterations of approximation. This number (3) is + * definitely optimal + */ + + y = 0.5 * (y + x / y); + y = 0.5 * (y + x / y); + y = 0.5 * (y + x / y); + + return y; +} |