213b954a90
- Add check in roundx() functions for infinite or NaN cases - Add block to avoid style warnings - Define long double constants and macros for infinity and nan - Correct return syntax to match NuttX style - Make c89 compliant - Fix definitions of INFINITY_L/NAN_L * include/nuttx/lib/math.h - match standard naming conventions - Rename isinf_l to isinfl - Rename isinf_f to isinff - Add finite() - Add finitel() - Add finitef() - Define isnanl and isnanf - Define isfinite() so that it uses the appropriate macro * libs/libc/math/lib_asinf.c libs/libc/math/lib_asinl.c libs/libc/math/lib_roundf.c libs/libc/math/lib_roundl.c libs/libc/math/lib_sqrtf.c libs/libc/math/lib_sqrtl.c - Use renamed macros - Use correct NAN_x or INFINIT_x macro on returns
115 lines
3.2 KiB
C
115 lines
3.2 KiB
C
/****************************************************************************
|
|
* libs/libc/math/lib_logf.c
|
|
*
|
|
* This file is a part of NuttX:
|
|
*
|
|
* Copyright (C) 2012, 2017-2018 Gregory Nutt. All rights reserved.
|
|
* Ported by: Darcy Gong
|
|
*
|
|
* It derives from the Rhombus OS math library by Nick Johnson which has
|
|
* a compatible, MIT-style license:
|
|
*
|
|
* 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.
|
|
*
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#include <math.h>
|
|
#include <float.h>
|
|
|
|
/****************************************************************************
|
|
* Pre-processor Definitions
|
|
****************************************************************************/
|
|
|
|
#define FLT_MAX_EXP_X 88.0F
|
|
|
|
/* To avoid looping forever in particular corner cases, every LOGF_MAX_ITER
|
|
* the error criteria is relaxed by a factor LOGF_RELAX_MULTIPLIER.
|
|
* todo: might need to adjust the double floating point version too.
|
|
*/
|
|
|
|
#define LOGF_MAX_ITER 10
|
|
#define LOGF_RELAX_MULTIPLIER 2.0F
|
|
|
|
/****************************************************************************
|
|
* Public Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: logf
|
|
****************************************************************************/
|
|
|
|
float logf(float x)
|
|
{
|
|
float y;
|
|
float y_old;
|
|
float ey;
|
|
float epsilon;
|
|
float relax_factor;
|
|
int iter;
|
|
|
|
y = 0.0F;
|
|
y_old = 1.0F;
|
|
epsilon = FLT_EPSILON;
|
|
|
|
iter = 0;
|
|
relax_factor = 1.0F;
|
|
|
|
while (y > y_old + epsilon || y < y_old - epsilon)
|
|
{
|
|
y_old = y;
|
|
ey = expf(y);
|
|
y -= (ey - x) / ey;
|
|
|
|
if (y > FLT_MAX_EXP_X)
|
|
{
|
|
y = FLT_MAX_EXP_X;
|
|
}
|
|
|
|
if (y < -FLT_MAX_EXP_X)
|
|
{
|
|
y = -FLT_MAX_EXP_X;
|
|
}
|
|
|
|
epsilon = (fabsf(y) > 1.0F) ? fabsf(y) * FLT_EPSILON : FLT_EPSILON;
|
|
|
|
if (++iter >= LOGF_MAX_ITER)
|
|
{
|
|
relax_factor *= LOGF_RELAX_MULTIPLIER;
|
|
iter = 0;
|
|
}
|
|
|
|
if (relax_factor > 1.0F)
|
|
{
|
|
epsilon *= relax_factor;
|
|
}
|
|
}
|
|
|
|
if (y == FLT_MAX_EXP_X)
|
|
{
|
|
return INFINITY_F;
|
|
}
|
|
|
|
if (y == -FLT_MAX_EXP_X)
|
|
{
|
|
return INFINITY_F;
|
|
}
|
|
|
|
return y;
|
|
}
|