diff options
Diffstat (limited to 'nuttx/lib/math/lib_log.c')
-rw-r--r-- | nuttx/lib/math/lib_log.c | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/nuttx/lib/math/lib_log.c b/nuttx/lib/math/lib_log.c new file mode 100644 index 000000000..62af0368a --- /dev/null +++ b/nuttx/lib/math/lib_log.c @@ -0,0 +1,113 @@ +/* + * Copyright (C) 2009, 2010 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. + */ + +#include <apps/math.h> +#include <float.h> + +float logf(float x) { + float y, y_old, ey, epsilon; + + y = 0.0; + y_old = 1.0; + epsilon = FLT_EPSILON; + + while (y > y_old + epsilon || y < y_old - epsilon) { + y_old = y; + ey = exp(y); + y -= (ey - x) / ey; + + if (y > 700.0) { + y = 700.0; + } + if (y < -700.0) { + y = -700.0; + } + + epsilon = (fabs(y) > 1.0) ? fabs(y) * FLT_EPSILON : FLT_EPSILON; + } + + if (y == 700.0) { + return INFINITY; + } + if (y == -700.0) { + return INFINITY; + } + + return y; +} + +double log(double x) { + double y, y_old, ey, epsilon; + + y = 0.0; + y_old = 1.0; + epsilon = DBL_EPSILON; + + while (y > y_old + epsilon || y < y_old - epsilon) { + y_old = y; + ey = exp(y); + y -= (ey - x) / ey; + + if (y > 700.0) { + y = 700.0; + } + if (y < -700.0) { + y = -700.0; + } + + epsilon = (fabs(y) > 1.0) ? fabs(y) * DBL_EPSILON : DBL_EPSILON; + } + + if (y == 700.0) { + return INFINITY; + } + if (y == -700.0) { + return INFINITY; + } + + return y; +} + +long double logl(long double x) { + long double y, y_old, ey, epsilon; + + y = 0.0; + y_old = 1.0; + epsilon = 1e-6; //fixme + + while (y > y_old + epsilon || y < y_old - epsilon) { + y_old = y; + ey = expl(y); + y -= (ey - x) / ey; + + if (y > 700.0) { + y = 700.0; + } + if (y < -700.0) { + y = -700.0; + } + } + + if (y == 700.0) { + return INFINITY; + } + if (y == -700.0) { + return INFINITY; + } + + return y; +} + |