diff options
Diffstat (limited to 'nuttx/lib/math/lib_sqrt.c')
| -rw-r--r-- | nuttx/lib/math/lib_sqrt.c | 179 |
1 files changed, 81 insertions, 98 deletions
diff --git a/nuttx/lib/math/lib_sqrt.c b/nuttx/lib/math/lib_sqrt.c index 206a7fe82..96f0d5409 100644 --- a/nuttx/lib/math/lib_sqrt.c +++ b/nuttx/lib/math/lib_sqrt.c @@ -1,4 +1,14 @@ -/* +/************************************************************************ + * lib/math/lib_sqrt.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 @@ -12,105 +22,78 @@ * 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. - */ + * + ************************************************************************/ -#include <stdint.h> -#include <float.h> -#include <errno.h> -#include <apps/math.h> - -static float __sqrt_approx(float x) { - int32_t i; - - // floats + bit manipulation = +inf fun! - i = *((int32_t*) &x); - i = 0x1FC00000 + (i >> 1); - x = *((float*) &i); - - return x; -} - -float sqrtf(float x) { - float y; +/************************************************************************ + * Included Files + ************************************************************************/ - // 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; +#include <nuttx/config.h> +#include <nuttx/compiler.h> - // guess square root (using bit manipulation) - y = __sqrt_approx(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; -} - -double sqrt(double x) { - long double y, y1; - - // 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 = __sqrt_approx(x); - - // perform four iterations of approximation - // this number (4) is definitely optimal - y = 0.5 * (y + x / y); - y = 0.5 * (y + x / y); - y = 0.5 * (y + x / y); - y = 0.5 * (y + x / y); - - // if guess was terribe (out of range of float) - // repeat approximation until convergence - if (y * y < x - 1.0 || y * y > x + 1.0) { - y1 = -1.0; - while (y != y1) { - y1 = y; - y = 0.5 * (y + x / y); - } - } - - return y; -} +#include <math.h> +#include <errno.h> -long double sqrtl(long double x) { - long double y, y1; - - // 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 = __sqrt_approx(x); - - // perform four iterations of approximation - // this number (4) is definitely optimal - y = 0.5 * (y + x / y); - y = 0.5 * (y + x / y); - y = 0.5 * (y + x / y); - y = 0.5 * (y + x / y); - - // if guess was terribe (out of range of float) - // repeat approximation until convergence - if (y * y < x - 1.0 || y * y > x + 1.0) { - y1 = -1.0; - while (y != y1) { - y1 = y; - y = 0.5 * (y + x / y); - } - } - - return y; +#include "lib_internal.h" + +/************************************************************************ + * Public Functions + ************************************************************************/ + +#if CONFIG_HAVE_DOUBLE +double sqrt(double x) +{ + long double y, y1; + + 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 four iterations of approximation. This number (4) is + * definitely optimal + */ + + y = 0.5 * (y + x / y); + y = 0.5 * (y + x / y); + y = 0.5 * (y + x / y); + y = 0.5 * (y + x / y); + + /* If guess was terribe (out of range of float). Repeat approximation + * until convergence. + */ + + if (y * y < x - 1.0 || y * y > x + 1.0) + { + y1 = -1.0; + while (y != y1) + { + y1 = y; + y = 0.5 * (y + x / y); + } + } + + return y; } +#endif |